How to make a really good board at home. How to make a printed circuit board at home How to make a printed circuit board at home

What is a printed circuit board

A printed circuit board (English printed circuit board, PCB, or printed wiring board, PWB) is a dielectric plate, on the surface and / or in the volume of which electrically conductive circuits of an electronic circuit are formed. The printed circuit board is designed for electrical and mechanical connection of various electronic components. Electronic components on a printed circuit board are connected with their leads to the elements of the conductive pattern, usually by soldering.

In contrast to surface mounting, on a printed circuit board, the electrically conductive pattern is made of foil, entirely located on a solid insulating base. The printed circuit board contains mounting holes and pads for mounting pin or planar components. In addition, printed circuit boards have vias for electrical connection of foil sections located on different layers of the board. From the outside, the board is usually coated with a protective coating (“solder mask”) and markings (an auxiliary figure and text according to the design documentation).

Depending on the number of layers with an electrically conductive pattern, printed circuit boards are divided into:

single-sided (SPP): there is only one layer of foil glued to one side of the dielectric sheet.

double-sided (DPP): two layers of foil.

multilayer (MPP): foil not only on two sides of the board, but also in the inner layers of the dielectric. Multilayer printed circuit boards are obtained by gluing several single or double sided boards together.

As the complexity of the designed devices and the density of mounting increase, the number of layers on the boards increases.

The basis of the printed circuit board is a dielectric, the most commonly used materials are fiberglass, getinaks. Also, a metal base coated with a dielectric (for example, anodized aluminum) can serve as the basis for printed circuit boards; copper foil tracks are applied over the dielectric. Such printed circuit boards are used in power electronics for efficient heat removal from electronic components. In this case, the metal base of the board is attached to the radiator. As a material for printed circuit boards operating in the microwave range and at temperatures up to 260 ° C, fluoroplastic reinforced with glass fabric (for example, FAF-4D) and ceramics are used. Flexible boards are made from polyimide materials such as Kapton.

What material will we use for the manufacture of boards

The most common, affordable materials for the manufacture of circuit boards are Getinaks and Steklotekstolit. Getinax paper impregnated with bakelite varnish, fiberglass textolite with epoxy. We will definitely use fiberglass!

Foiled fiberglass is sheets made on the basis of glass fabrics impregnated with a binder based on epoxy resins and lined on both sides with copper electrolytic galvanic-resistant foil 35 microns thick. The maximum allowable temperature is from -60ºС to +105ºС. It has very high mechanical and electrical insulating properties, lends itself well to machining by cutting, drilling, stamping.

Fiberglass is mainly used one or two-sided with a thickness of 1.5mm and with copper foil with a thickness of 35μm or 18μm. We will use a 0.8mm thick single-sided fiberglass with a 35µm thick foil (why will be discussed in detail later).

Methods for making printed circuit boards at home

Boards can be manufactured chemically and mechanically.

With the chemical method, in those places where there should be tracks (drawing) on ​​the board, a protective composition (lacquer, toner, paint, etc.) is applied to the foil. Next, the board is immersed in a special solution (ferric chloride, hydrogen peroxide, and others), which "corrodes" the copper foil, but does not affect the protective composition. As a result, copper remains under the protective composition. The protective composition is subsequently removed with a solvent and the finished board remains.

The mechanical method uses a scalpel (for manual production) or a milling machine. A special cutter makes grooves on the foil, eventually leaving islands with foil - the necessary pattern.

Milling machines are quite expensive, as well as the cutters themselves are expensive and have a small resource. So, we will not use this method.

The simplest chemical method is manual. With a risograph varnish, tracks are drawn on the board and then we etch with a solution. This method does not allow making complex boards with very thin traces - so this is not our case either.

The next method for making boards is with a photoresist. This is a very common technology (boards are made by this method at the factory) and it is often used at home. There are a lot of articles and methods for manufacturing boards using this technology on the Internet. It gives very good and repeatable results. However, this is also not our option. The main reason is rather expensive materials (photoresist, which also deteriorates over time), as well as additional tools (UV lamp, laminator). Of course, if you have a bulk production of boards at home - then the photoresist is out of competition - we recommend mastering it. It is also worth noting that the equipment and technology of photoresist allows the production of silk-screen printing and protective masks on circuit boards.

With the advent of laser printers, radio amateurs began to actively use them for the manufacture of circuit boards. As you know, a laser printer uses "toner" to print. This is a special powder that sinters under temperature and sticks to paper - as a result, a pattern is obtained. The toner is resistant to various chemicals, which allows it to be used as a protective coating on the copper surface.

So, our method is to transfer the toner from the paper to the surface of the copper foil and then etch the board with a special solution to obtain a pattern.

Due to its ease of use, this method has earned a very wide distribution in amateur radio. If you type in Yandex or Google how to transfer the toner from paper to the board, you will immediately find such a term as "LUT" - laser ironing technology. Boards using this technology are made as follows: a pattern of tracks is printed in a mirror version, paper is applied to the board with a pattern to copper, we iron this paper on top, the toner softens and sticks to the board. The paper is further soaked in water and the board is ready.

There are "a million" articles on the Internet about how to make a board using this technology. But this technology has many disadvantages that require direct hands and a very long attachment to it. That is, you have to feel it. Payments do not come out the first time, they are obtained every other time. There are many improvements - to use a laminator (with alteration - in the usual one there is not enough temperature), which allow to achieve very good results. There are even methods for building special heat presses, but all this again requires special equipment. The main disadvantages of LUT technology:

overheating - the tracks spread out - become wider

underheating - tracks remain on paper

the paper is “cooked” to the board - even when it is soaked, it is difficult to leave - as a result, the toner may be damaged. There is a lot of information on the Internet about which paper to choose.

Porous toner - after removing the paper, micropores remain in the toner - the board is also etched through them - corroded tracks are obtained

repeatability of the result - excellent today, bad tomorrow, then good - it is very difficult to achieve a stable result - you need a strictly constant toner warm-up temperature, you need a stable board pressure.

By the way, this method did not work for me to make a board. Tried to do both on magazines and on coated paper. As a result, he even spoiled the boards - copper swelled from overheating.

For some reason, there is undeservedly little information on the Internet about another method of toner transfer - the method of cold chemical transfer. It is based on the fact that toner does not dissolve with alcohol, but with acetone. As a result, if you choose such a mixture of acetone and alcohol, which will only soften the toner, then it can be “re-pasted” onto the board from paper. I really liked this method and immediately paid off - the first board was ready. However, as it turned out later, I could not find detailed information anywhere that would give a 100% result. We need a method by which even a child could make a payment. But for the second time, the payment did not work out, then again it took a long time to select the necessary ingredients.

As a result, after a long time, a sequence of actions was developed, all components were selected that give, if not 100% then 95% of a good result. And most importantly, the process is so simple that the child can make the payment completely on his own. This is the method we will use. (Of course, it can be further improved to the ideal - if it works out better for you, then write). The advantages of this method:

all reagents are inexpensive, available and safe

no additional tools are needed (irons, lamps, laminators - nothing, although not - you need a pan)

there is no way to spoil the board - the board does not heat up at all

paper moves away by itself - you can see the result of the transfer of toner - where the transfer did not come out

there are no pores in the toner (they are sealed with paper) - accordingly, there are no mordants

do 1-2-3-4-5 and always get the same result - almost 100% repeatability

Before we start, let's see what boards we need, and what we can do at home with this method.

Basic requirements for manufactured boards

We will make devices on microcontrollers, using modern sensors and microcircuits. Microcircuits are getting smaller and smaller. Accordingly, the following requirements must be met:

boards must be two-sided (as a rule, it is very difficult to separate a single-sided board, it is rather difficult to make four-layer boards at home, microcontrollers need a ground layer to protect against interference)

the tracks should be 0.2mm thick - this size is quite enough - 0.1mm would be even better - but there is a possibility of pickling, track departure during soldering

the gaps between the tracks - 0.2mm - this is enough for almost all circuits. Reducing the gap to 0.1mm is fraught with merging of tracks and difficulty in monitoring the board for short circuits.

We will not use protective masks, and also do silk-screening - this will complicate the production, and if you are making the board for yourself, then this is not necessary. Again, there is a lot of information on the Internet on this topic, and if you wish, you can make a “marafet” yourself.

We will not tinker with the boards, this is also not necessary (unless you are making a device for 100 years). For protection, we will use varnish. Our main goal is to quickly, efficiently, cheaply make a board for the device at home.

This is what the finished board looks like. made by our method - tracks 0.25 and 0.3, distances 0.2

How to make a double-sided board from 2 single-sided

One of the problems with making double-sided boards is aligning the sides so that the vias line up. Usually a "sandwich" is made for this. 2 sides are printed on a sheet of paper at once. The sheet is bent in half, the sides are precisely aligned with the help of special marks. Double-sided textolite is inserted inside. With the LUT method, such a sandwich is ironed and a double-sided board is obtained.

However, in the cold transfer toner method, the transfer itself is carried out with the help of a liquid. And therefore it is very difficult to organize the process of wetting one side simultaneously with the other side. Of course, this can also be done, but with the help of a special device - a mini press (vice). Thick sheets of paper are taken - which absorb the toner transfer fluid. The sheets are wetted so that the liquid does not drip and the sheet holds its shape. And then a “sandwich” is made - a wetted sheet, a sheet of toilet paper to absorb excess liquid, a sheet with a pattern, a double-sided board, a sheet with a pattern, a sheet of toilet paper, again a wetted sheet. All this is clamped vertically in a vise. But we will not do this, we will do it easier.

A very good idea slipped through the board manufacturing forums - what a problem it is to make a double-sided board - we take a knife and cut the textolite in half. Since fiberglass is a puff material, it is not difficult to do this with a certain skill:

As a result, from one double-sided board with a thickness of 1.5 mm, we get two one-sided halves.

Next, we make two boards, drill and that's it - they are perfectly aligned. It was not always possible to cut the textolite evenly, and as a result, the idea came up to immediately use a thin one-sided textolite with a thickness of 0.8 mm. Then you can not glue the two halves, they will be held by soldered jumpers in vias, buttons, connectors. But if necessary, you can glue it with epoxy glue without any problems.

The main advantages of this trip:

Textolite with a thickness of 0.8 mm is easily cut with scissors on paper! In any shape, that is, it is very easy to cut to fit the body.

Thin textolite - transparent - by shining a lantern from below, you can easily check the correctness of all tracks, short circuits, breaks.

Soldering one side is easier - the components on the other side do not interfere and you can easily control the soldering of microcircuit pins - you can connect the sides at the very end

You need to drill twice as many holes and the holes may slightly misalign.

The rigidity of the structure is slightly lost if you do not glue the boards, and gluing is not very convenient

One-sided fiberglass 0.8mm thick is difficult to buy, mostly 1.5mm is sold, but if you couldn’t get it, you can cut a thicker textolite with a knife.

Let's move on to the details.

Necessary tools and chemistry

We will need the following ingredients:

Now that all this is there, let's do it step by step.

1. Layout of board layers on a sheet of paper for printing using InkScape

Automatic collet set:

We recommend the first option - it is cheaper. Next, you need to solder wires and a switch to the motor (preferably a button). It is better to place the button on the body, so that it is more convenient to quickly turn the motor on and off. It remains to choose a power supply, you can take any power supply for 7-12V with a current of 1A (or less), if there is no such power supply, then charging via USB at 1-2A or a Kron battery may be suitable (you just need to try - not all chargers like motors, the motor may not start).

The drill is ready, you can drill. But it is only necessary to drill strictly at an angle of 90 degrees. You can build a mini machine - there are various schemes on the Internet:

But there is an easier solution.

Drill jig

To drill exactly at 90 degrees, it is enough to make a drilling jig. We'll do something like this:

It is very easy to make it. We take a square of any plastic. We put our drill on a table or other flat surface. And we drill a hole in the plastic with the right drill. It is important to ensure a smooth horizontal displacement of the drill. You can lean the motor against a wall or rail and plastic too. Next, use a large drill to drill a hole for the collet. On the reverse side, drill or cut off a piece of plastic so that the drill can be seen. A non-slip surface can be glued to the bottom - paper or an elastic band. Such a conductor must be made for each drill. This will ensure perfectly accurate drilling!

This option is also suitable, cut off the top part of the plastic and cut off the corner from the bottom.

Here is how drilling is done with it:

We clamp the drill so that it sticks out 2-3 mm when the collet is fully immersed. We put the drill in the place where it is necessary to drill (when etching the board, we will have a mark where to drill in the form of a mini hole in copper - in Kicad we specially set a checkbox for this, so that the drill will get up there by itself), press the conductor and turn on the motor - the hole ready. For illumination, you can use a flashlight by placing it on the table.

As we wrote earlier, you can only drill holes on one side - where the tracks fit - the second half can be drilled without a jig along the first guide hole. This saves some power.

8. Tinning board

Why tin boards - mainly to protect copper from corrosion. The main disadvantage of tinning is overheating of the board, possible damage to the tracks. If you do not have a soldering station - definitely - do not tin the board! If it is, then the risk is minimal.

It is possible to tin the board with ROSE alloy in boiling water, but it is expensive and difficult to obtain. It is better to tin with ordinary solder. To do this qualitatively, a very thin layer must be made a simple device. We take a piece of braid for soldering parts and put it on the sting, fasten it with a wire to the sting so that it does not come off:

We cover the board with a flux - for example, LTI120 and a braid too. Now we collect tin into the braid and we drive it along the board (we paint it) - we get an excellent result. But with use, the braid falls apart and copper fibers begin to remain on the board - they must be removed, otherwise there will be a short circuit! It is very easy to see this by shining a flashlight on the back of the board. With this method, it is good to use either a powerful soldering iron (60 watts) or ROSE alloy.

As a result, it is better not to tin the boards, but to varnish at the very end - for example, PLASTIC 70, or a simple acrylic varnish bought in auto parts KU-9004:

Fine tuning of the toner transfer method

There are two points in the method that are amenable to tuning, and may not work right away. To set them up, you need to make a test board in Kicad, tracks in a square spiral of different thicknesses, from 0.3 to 0.1 mm and at different intervals, from 0.3 to 0.1 mm. It is better to immediately print several of these samples on one sheet and adjust.

Possible issues we will be fixing:

1) tracks can change geometry - spread, become wider, usually not very much, up to 0.1mm - but this is not good

2) the toner may not adhere well to the board, move away when removing the paper, it may not adhere well to the board

The first and second problems are interrelated. I solve the first, you come to the second. We must find a compromise.

The tracks can spread for two reasons - too much clamping weight, too much acetone in the composition of the resulting liquid. First of all, you need to try to reduce the load. The minimum load is about 800g, you should not reduce it below. Accordingly, we put the load without any pressure - we just put it on top and that's it. Be sure to have 2-3 layers of toilet paper for good absorption of excess solution. You must ensure that after removing the load, the paper should be white, without purple smudges. Such smudges indicate a strong melting of the toner. If it was not possible to adjust the load with the load, the tracks still blur, then we increase the proportion of nail polish remover in the solution. Can be increased to 3 parts liquid and 1 part acetone.

The second problem, if there is no geometry violation, indicates an insufficient weight of the cargo or a small amount of acetone. Again, it's worth starting with the load. More than 3 kg does not make sense. If the toner still does not adhere well to the board, then you need to increase the amount of acetone.

This problem mostly occurs when you change your nail polish remover. Unfortunately, this is not a permanent and not a pure component, but it was not possible to replace it with another one. I tried to replace it with alcohol, but apparently the mixture is not homogeneous and the toner sticks with some inclusions. Also, nail polish remover may contain acetone, then it will need less. In general, you will need to carry out such tuning once until the liquid runs out.

Board ready

If you do not immediately solder the board, then it must be protected. The easiest way to do this is to coat with alcohol rosin flux. Before soldering, this coating will need to be removed, for example, with isopropyl alcohol.

Alternatives

You can also make a payment:

Additionally, a custom board manufacturing service is now gaining popularity - for example, Easy EDA. If a more complex board is needed (for example, a 4-layer board), then this is the only way out.

I don’t know about you, but I have a fierce hatred for classic circuit boards. A montage is such crap with holes where you can insert parts and solder, where all connections are made through wiring. It seems to be simple, but it turns out such a mess that it is very problematic to understand anything in it. Therefore, errors and burnt parts, incomprehensible glitches. Well fuck her. Only to spoil the nerves. It is much easier for me to draw a schematic in my favorite and immediately etch it in the form of a printed circuit board. Using laser-ironing method everything comes out for what that one and a half hours of easy work. And, of course, this method is great for making the final device, since the quality of printed circuit boards obtained by this method is very high. And since this method is very difficult for the inexperienced, I will gladly share my proven technology, which allows you to get printed circuit boards the first time and without any strain. with tracks 0.3mm and clearance between them up to 0.2mm. As an example, I will make a debug board for my controller tutorial. AVR. You will find the principal in the entry, and

There is a demo diagram on the board, as well as a lot of copper patches, which can also be drilled and used for your needs, like a regular circuit board.

▌Technology for manufacturing high-quality printed circuit boards at home.

The essence of the method of manufacturing printed circuit boards is that a protective pattern is applied to the foil textolite, which prevents copper from etching. As a result, after etching, traces of conductors remain on the board. There are many ways to apply protective drawings. Previously, they were drawn with nitro paint, using a glass tube, then they began to be applied with waterproof markers or even cut out of adhesive tape and pasted onto the board. Also available for amateur use photoresist, which is applied to the board, and then illuminated. Illuminated areas become soluble in alkali and washed off. But in terms of ease of use, low cost and speed of manufacture, all these methods lose a lot. laser ironing method(Further LUT).

The LUT method is based on the fact that the protective pattern is formed by toner, which is transferred to the textolite by heating.
So we need a laser printer, since they are not uncommon now. I am using a printer Samsung ML1520 with original cartridge. Refilled cartridges fit extremely poorly, as they lack the density and uniformity of toner delivery. In the print properties, you need to set the maximum density and contrast of the toner, be sure to disable all saving modes - this is not the case.

▌Tool and materials
In addition to foil textolite, we also need a laser printer, iron, photo paper, acetone, fine sandpaper, a suede brush with metal-plastic pile,

▌Process
Then we draw a drawing of the board in any software convenient for us and print it. Sprint layout. Simple drawing for boards. To print normally, you need to set the colors of the layers to black on the left. Otherwise it will be bullshit.

Printout, two copies. You never know, suddenly we mess up one.

Here lies the main subtlety of the technology LUT because of which many people have problems with the release of high-quality boards and they quit this business. Through many experiments, it has been found that the best result is achieved when printing on glossy inkjet photo paper. I would call photo paper ideal LOMOND 120g/m2

It is inexpensive, sold everywhere, and most importantly, it gives an excellent and repeatable result, and does not burn with its glossy layer to the printer's stove. This is very important, as I have heard of cases where the printer oven was crap with glossy paper.

We load paper into the printer and boldly print on the glossy side. You need to print in mirror image so that after transferring the picture is true. How many times I made mistakes and made wrong prints, do not count :) Therefore, the first time it is better to print on plain paper for testing and check that everything is correct. At the same time, warm up the printer's oven.

After printing the picture, in no case can not be grabbed by hands and preferably protected from dust. So that nothing interferes with the contact of the toner and copper. Next, cut out the board pattern exactly along the contour. Without any stock - the paper is stiff, so everything will be fine.

Now let's deal with textolite. We will immediately cut out a piece of the desired size, without tolerances and allowances. As much as needs.

It needs to be well sanded. Carefully, trying to tear off all the oxide, preferably in a circular motion. A little roughness won't hurt - the toner will stick better. You can take not a skin, but an abrasive sponge "effect". Just need to take a new one, not greasy.

It is better to take the smallest skin you can find. I have this one.

After sanding, it must be carefully degreased in the same way. I usually rub a cotton pad from my wife and, having moistened it properly with acetone, I carefully walk over the entire surface. Again, after degreasing, in no case should you grab it with your fingers.

We impose our drawing on the board, naturally with the toner down. warm up iron to the max, holding the paper with your finger, press well and iron one half. It is necessary that the toner sticks to the copper.

Next, without allowing the paper to move, we iron the entire surface. We press with all our might, polish and iron the board. Trying not to miss a millimeter of the surface. This is the most important operation, the quality of the entire board depends on it. Don't be afraid to press as hard as you can, the toner won't float or smudge, as the photo paper is thick and perfectly protects it from spreading.

We iron until the paper turns yellow. However, this depends on the temperature of the iron. It almost does not turn yellow on my new iron, but on the old one it almost charred - the result was equally good everywhere.

After that, you can let the board cool down a bit. And then, grabbing it with tweezers, we put it under the water. And keep some time in the water, usually two or three minutes.

Taking a brush for suede, under a strong stream of water, we begin to furiously lift the outer surface of the paper. We need to cover it with multiple scratches so that the water penetrates deep into the paper. In confirmation of your actions, there will be a manifestation of the drawing through thick paper.

And with this brush we dry the board until we remove the top layer.

When the whole drawing is clearly visible, without white spots, then you can start carefully, rolling the paper from the center to the edges. Paper lomond rolls great, leaving 100% toner and pure copper almost immediately.

Having rolled the entire pattern with your fingers, you can thoroughly scrape the entire board with a toothbrush to clean out the remnants of the glossy layer and scraps of paper. Don't be afraid, it's almost impossible to remove a well-seasoned toner with a toothbrush.

We wipe the board and let it dry. When the toner dries and turns gray, it will be clearly visible where the paper is left, and where everything is clean. Whitish films between the tracks must be removed. You can destroy them with a needle, or you can tear them with a toothbrush under running water. In general, it is useful to brush along the paths. Whitish gloss can be pulled out of narrow slots with electrical tape or masking tape. It sticks not as violently as usual and does not break off the toner. But the remnants of gloss tears off without a trace and immediately.

Under the light of a bright lamp, carefully examine the layers of toner for breaks. The fact is that when cooled, it can crack, then a narrow crack will remain in this place. The cracks gleam under the lamplight. These areas should be touched up with a permanent marker for CDs. Even if there is only a suspicion, it is still better to paint over. With the same marker, you can also draw low-quality tracks, if any. I recommend the marker Centropen 2846- it gives a thick layer of paint and, in fact, they can stupidly draw paths.

When the board is ready, you can bodyaze a solution of ferric chloride.

Technical digression, if you wish, you can skip it
In general, you can poison a lot of things. Someone poisons in blue vitriol, someone in acid solutions, and I in ferric chloride. Because it is sold in any radio store, poisons quickly and cleanly.
But ferric chloride has a terrible drawback - it just gets dirty with a scribe. It will get on clothes or any porous surface like wood or paper, everything, consider the stain for life. So dive your Dolce Gabana sweatshirts or Gucci boots into the safe and wrap three rolls of tape around them. And ferric chloride in the most cruel way destroys almost all metals. Especially fast aluminum and copper. So etching dishes should be glass or plastic.

I throw 250 gram package of ferric chloride per liter of water. And with the resulting solution, I poison dozens of boards until it stops poisoning.
The powder must be poured into the water. And make sure that the water does not overheat, otherwise the reaction proceeds with the release of a large amount of heat.

When the powder is all dissolved and the solution acquires a uniform color, you can throw a board there. It is desirable that the board float on the surface, copper down. Then the precipitate will fall to the bottom of the tank, without interfering with the etching of deeper layers of copper.
To prevent the board from sinking, you can stick a piece of foam to it on double-sided tape. That's exactly what I did. It turned out very convenient. I screwed in the screw for convenience, to hold on to it like a handle.

It is better to dip the board several times into the solution, and lower it not flat, but at an angle so that air bubbles do not remain on the copper surface, otherwise there will be jambs. Periodically it is necessary to get out of the solution and monitor the process. On average, the etching of the board takes from ten minutes to an hour. It all depends on the temperature, strength and freshness of the solution.

The etching process accelerates very sharply if you lower the hose from the aquarium compressor under the board and blow bubbles. The bubbles stir the solution and gently knock out the reacted copper from the board. You can also shake the board or container, the main thing is not to spill it, otherwise you won’t wash it off later.

When all the copper is etched, then carefully remove the board and rinse under running water. Then we look at the clearance, so that there is no snot and undergrass anywhere. If there is snot, then we throw another ten minutes into the solution. If the tracks are etched or there are breaks, then the toner is crooked and these places will need to be soldered with copper wire.

If all is well, then you can wash off the toner. To do this, we need acetone - a true friend of a drug addict. Although now it is becoming more difficult to buy acetone, because. some idiot from the state drug control decided that acetone is a substance used to make drugs, which means that its free sale should be banned. Works well in place of acetone 646 solvent.

We take a piece of bandage and thoroughly wetting it with acetone, we begin to wash off the toner. You don’t need to press hard, the main thing is not to move too fast, so that the solvent has time to be absorbed into the pores of the toner, corroding it from the inside. It takes two or three minutes to flush the toner. During this time, even green dogs under the ceiling will not have time to appear, but it still does not hurt to open the window.

The washed board can be drilled. For these purposes, for many years I have been using a motor from a tape recorder, powered by 12 volts. The monster machine, though its resource is enough for about 2000 holes, after which the brushes burn out completely. And you also need to tear out the stabilization circuit from it by soldering the wires directly to the brushes.

When drilling, try to keep the drill strictly perpendicular. Otherwise, then you'll put the damn chip in there. And with double-sided boards, this principle becomes the main one.

The manufacture of a double-sided board also occurs, only here three reference holes are made, as small as possible in diameter. And after etching one side (the other at this time is sealed with adhesive tape so that it does not etch), the second side is combined through these holes and rolled. The first is sealed tightly with adhesive tape and the second is poisoned.

On the front side, you can apply the designation of radio components using the same LUT method, for beauty and ease of installation. However, I don’t bother like that, but comrade Woodocat from LJ community ru_radio_electric does so always, for which he has great respect!

Soon I will probably also publish an article on photoresist. The method is more confusing, but at the same time, it’s more fun for me to do it - I like to fool around with reagents. Although I still make 90% of the boards with LUT.

By the way, about the accuracy and quality of the boards made by the laser ironing method. Controller P89LPC936 in the building TSSOP28. The distance between the tracks is 0.3mm, the width of the tracks is 0.3mm.

Resistors on the top board 1206 . What is it?

When a laser printer is available, radio amateurs use a printed circuit board manufacturing technology called LUT. However, such a device is not available in every home, since even in our time it is quite expensive. There is also a manufacturing technology using a photoresistive film. However, to work with it, you also need a printer, but already an inkjet. It’s already easier, but the film itself is quite expensive, and at first it’s better for a novice radio amateur to spend the available funds on a good soldering station and other accessories.
Is it possible to make an acceptable quality printed circuit board at home without a printer? Yes. Can. Moreover, if everything is done as described in the material, it will take quite a bit of money and time, and the quality will be at a very high level. In any case, the electric current will “run” along such paths with great pleasure.

List of necessary tools and consumables

It’s worth starting with the preparation of tools, fixtures and consumables, without which you simply cannot do. To implement the most budgetary way to manufacture printed circuit boards at home, you will need the following:

1. Drawing design software.
2. Transparent polyethylene film.
3. Narrow tape.
4. Marker.
5. Foil fiberglass.
6. Sandpaper.
7. Alcohol.
8. Unused toothbrush.
9. Tool for drilling holes with a diameter of 0.7 to 1.2 mm.
10. Ferric chloride.
11. Plastic pickling container.
12. Paint brush.
13. Soldering iron.
14. Solder.
15. Liquid flux.

Let's go through each point briefly, as there are some nuances that can only be reached by experience.
There are a huge number of PCB design programs today, but for a beginner radio amateur, Sprint Layout is the easiest option. It is easy to master the interface, you can use it for free, there is a huge library that includes common radio components.
Polyethylene is needed to transfer the picture from the monitor. It is better to take a film that is harder, for example, from old covers for school books. To attach it to the monitor, any adhesive tape is suitable. It is better to take a narrow one - it will be easier to peel off (this procedure does not harm the monitor).
It is worth dwelling on markers in more detail, as this is a sore subject. To transfer the pattern to polyethylene, in principle, any option is suitable. But for drawing on foil-coated fiberglass, you need a special marker. But there is a little trick here, how to save money and not buy quite expensive "special" markers for drawing printed circuit boards. The fact is that these products are absolutely no different in their properties from ordinary permanent markers, which are sold 5-6 times cheaper in any stationery store. But the marker must necessarily have the inscription "Permanent". Otherwise, nothing will work.

Foil fiberglass can be taken any. It's better if it's thicker. It is much easier for beginners to work with such material. To clean it, you will need sandpaper with a grit of about 1000 units, as well as alcohol (available in any pharmacy). The last consumable can be replaced with a liquid for reducing nail polish, which is in any house where a woman lives. However, this remedy smells rather nasty and disappears for a long time.
To drill the board, it is better to have a special mini-drill or engraver. However, you can also go the cheaper route. It is enough to buy a collet or cam chuck for small drills and adapt it to a regular household drill.
Ferric chloride can be replaced with other chemicals, including those that you probably already have in your home. For example, a solution of citric acid in hydrogen peroxide is suitable. Information on how ferric chloride alternative compositions for board etching are prepared can be easily found on the Web. The only thing worth paying attention to is the container for such chemistry - it should be plastic, acrylic, glass, but not metal at all.
It is not worth talking about a soldering iron, solder and liquid flux in more detail. If a radio amateur has reached the issue of manufacturing a printed circuit board, then he is probably already familiar with these things.

Development and transfer of the board pattern to the template

When all of the above tools, fixtures and consumables are prepared, you can take on the development of the board. If the device being manufactured is not unique, then it will be much easier to download its project from the Web. Even a regular JPEG image will do.

If you want to go the more difficult route, draw the board yourself. This option is often unavoidable, for example, in situations where you do not have exactly the same radio parts that are needed to assemble the original board. Accordingly, replacing components with analogues, you have to allocate space for them on fiberglass, adjust holes and tracks. If the project is unique, then the board will have to be developed from scratch. For this, the above software is needed.
When the board layout is ready, it remains only to transfer it to a transparent template. Polyethylene is fixed directly on the monitor with adhesive tape. Next, we simply translate the existing drawing - tracks, contact patches, and so on. For these purposes, it is best to use the same permanent marker. It does not rub off, does not smear, and is clearly visible.

Preparation of foil fiberglass

The next step is the preparation of fiberglass. First you need to cut it to the size of the future board. It is better to do this with a small margin. For cutting foil fiberglass, you can use one of several methods.
Firstly, the material is perfectly cut with a hacksaw. Secondly, if you have an engraver with cut-off wheels, it will be convenient to use it. Thirdly, fiberglass can be cut to size with a clerical knife. The cutting principle is the same as when working with a glass cutter - a cutting line is applied in several passes, then the material is simply broken off.

Now it is necessary to clean the copper layer of fiberglass from the protective coating and oxide. There is no better way than sandpapering to solve this problem. Grain is taken from 1000 to 1500 units. The goal is to get a clean, shiny surface. It is not worth polishing the copper layer to a mirror finish, since small scratches from sandpaper increase the adhesion of the surface, which will be needed next.
In conclusion, it remains only to clean the foil from dust and traces of your fingers. For this, alcohol or acetone (nail polish remover) is used. After processing, we do not touch the copper surface with our hands. For subsequent manipulations, we grab the fiberglass over the edges.

Combination of template and fiberglass

Now our task is to combine the pattern obtained on polyethylene with the prepared fiberglass. To do this, the film is applied to the right place and positioned. The rest is wrapped on the back side and fastened with the same adhesive tape.

Hole drilling

Before drilling, it is recommended to fix the fiberglass with a template on the surface in some way. This will achieve greater accuracy, as well as eliminate sudden turning of the material during the passage of the drill through. If you have a drilling machine for such work, then the described problem will not arise at all.

You can drill holes in fiberglass at any speed. Someone works at low speeds, someone at high speeds. Experience shows that the drills themselves last much longer if they are operated at low speeds. So they are more difficult to break, bend and damage the sharpening.
The holes are drilled straight through the polyethylene. The future contact patches drawn on the template will serve as guidelines. If the project requires it, then we change the drills to the required diameter in a timely manner.

Drawing tracks

Next, the template is removed, but not thrown away. We still try not to touch the copper coating with our hands. To draw tracks, we use a marker, always permanent. It can be clearly seen from the trail it leaves. It is better to draw in one pass, since after the varnish, which is part of the permanent marker, has hardened, it will be very difficult to make edits.

As a guide, we use the same polyethylene template. You can also draw in front of the computer, referring to the original layout, where there are markings and other notes. If possible, it is better to use several markers with tips of different thicknesses. This will allow you to draw both thin paths and large polygons with better quality.

After applying the pattern, be sure to wait for some time required for the final hardening of the varnish. You can even dry it with a hair dryer. The quality of future tracks will depend on this.

Etching and cleaning tracks from the marker

Now the most interesting thing is the etching of the board. There are several nuances that few people mention, but they significantly affect the quality of the result. First of all, we prepare a solution of ferric chloride according to the recommendations on the package. Usually the powder is diluted with water in a ratio of 1:3. And here is the first tip. Make the solution more saturated. This will help speed up the process, and the drawn paths will not fall off before everything that is needed is etched.

Immediately advice the second. It is recommended to immerse the solution bath in hot water. You can heat it in a metal bowl. An increase in temperature, as we know from the school curriculum, greatly speeds up the chemical reaction, which is the etching of our board. Reducing the time of the procedure is in our favor. The tracks applied by the marker are quite unstable, and the less they sour in the liquid, the better. If at room temperature the board in ferric chloride is etched for about an hour, then in warm water this process is reduced to 10 minutes.
Finally, one more piece of advice. During the etching process, although it is already accelerated by heating, it is recommended to constantly move the board, as well as brush off the reaction products with a paint brush. By combining all the manipulations described above, it is quite possible to etch excess copper in just 5-7 minutes, which is simply an excellent result for this technology.

At the end of the procedure, the board must be thoroughly rinsed under running water. Then we dry it. It remains only to wash off the traces of the marker, still covering our paths and patches. This is done with the same alcohol or acetone.

PCB tinning

Before tinning, we must once again go over the copper layer with sandpaper. But now we do it very carefully so as not to damage the tracks. The easiest and most affordable way of tinning is traditional, using a soldering iron, flux and solder. Rose or Wood alloys can also be used. There is also the so-called liquid tin on the market, which can greatly simplify the task.
But all these new technologies require additional costs and some experience, so the classic tinning method is also suitable for the first time. A liquid flux is applied to the cleaned tracks. Next, solder is collected on the tip of the soldering iron and distributed over the copper remaining after etching. It is important here to warm up the tracks, otherwise the solder may not “stick”.

If you still have Rose or Wood alloys, then they can be used without technology. They just melt wonderfully with a soldering iron, are easily distributed along the tracks, do not stray into lumps, which will only be a plus for a beginner radio amateur.

Conclusion

As can be seen from the above, the budget technology for manufacturing printed circuit boards at home is really affordable and inexpensive. No printer, no iron, no expensive photoresist film needed. Using all the above tips, you can easily make the simplest electronic ones without investing a lot of money in it, which is very important in the early stages of amateur radio.

How to prepare a board made in Eagle for production

Preparation for production consists of 2 stages: technology restrictions check (DRC) and generation of files in Gerber format

DRC

Every PCB manufacturer has technology restrictions on minimum trace widths, trace spacing, hole diameters, and so on. If the board does not meet these restrictions, the manufacturer refuses to accept the board for production.

When creating a PCB file, the default technology limits are set from the default.dru file in the dru directory. As a rule, these limits do not correspond to the limits of real manufacturers, so they need to be changed. You can set the limits just before generating the Gerber files, but it's better to do it right after the board file is generated. To set restrictions, press the DRC button

gaps

Go to the Clearance tab, where the gaps between the conductors are set. We see 2 sections: different signals and Same signals. different signals- defines gaps between elements belonging to different signals. Same signals- defines gaps between elements belonging to the same signal. When moving between input fields, the picture changes, showing the meaning of the input value. Dimensions can be specified in millimeters (mm) or thousandths of an inch (mil, 0.0254 mm).

Distances

The Distance tab defines the minimum distances between the copper and the edge of the board ( Copper/Dimension) and between the edges of the holes ( Drill/Hole)

Minimum dimensions

On the Sizes tab for double-sided boards, 2 parameters make sense: Minimum Width- minimum conductor width and Minimum Drill is the minimum hole diameter.

Belts

The Restring tab defines the sizes of the bands around the vias and pads of the output components. The width of the girdle is set as a percentage of the hole diameter, while you can set a limit on the minimum and maximum width. For double-sided boards, the parameters make sense Pads/Top, pads/bottom(pads on the top and bottom layers) and Via/Outer(through holes).

masks

On the Masks tab, the gaps from the edge of the pad to the solder mask are set ( stop) and solder paste ( Cream). Clearances are specified as a percentage of the smaller pad size, and you can set a limit on the minimum and maximum clearance. If the board manufacturer does not specify special requirements, you can leave the default values ​​​​on this tab.

Parameter limit defines the minimum via diameter that will not be covered by the mask. For example, if you specify 0.6mm, then vias with a diameter of 0.6mm or less will be masked.

Running a check

After setting the restrictions, go to the tab File. You can save the settings to a file by clicking the button. Save as.... In the future, for other boards, you can quickly load the settings ( Load...).

Push button apply the set technology limits apply to the PCB file. It affects layers tStop, bStop, tCream, bCream. Also, vias and pads on output components will be resized to fit the constraints set on the tab. Restring.

Button press Check starts the constraint control process. If the board satisfies all restrictions, the program status line will display the message No errors. If the board does not pass control, a window appears DRC Errors

The window contains a list of DRC errors, indicating the error type and layer. By double-clicking on a line, the area of ​​the board with the error will be shown in the center of the main window. Error types:

too little clearance

hole diameter too small

intersection of tracks with different signals

foil too close to board edge

After correcting the errors, you need to start the control again, and repeat this procedure until all errors are eliminated. The board is now ready to be output to Gerber files.

Gerber file generation

From the menu File choose CAM Processor. A window will appear CAM Processor.

The set of file generation parameters is called a task. The task consists of several sections. The section defines output parameters for a single file. Eagle comes with the gerb274x.cam task by default, but it has 2 drawbacks. Firstly, the lower layers are displayed in a mirror image, and secondly, the drill file is not output (one more task will have to be performed to generate the drill). Therefore, consider creating a task from scratch.

We need to create 7 files: board borders, copper top and bottom, silkscreen top, solder mask top and bottom, and drill.

Let's start with the borders of the board. In field Section enter the name of the section. Checking what's in the group style installed only pos. Coord, Optimize and Fill pads. From the list device choose GERBER_RS274X. In the input field File enter the name of the output file. It is convenient to place the files in a separate directory, so in this field we will enter %P/gerber/%N.Edge.grb . This means the directory where the board source file is located, the subdirectory gerber, the original board file name (without extension .brd) with added at the end .edge.grb. Note that subdirectories are not created automatically, so you will need to create a subdirectory before generating files gerber in the project directory. In the fields offset enter 0. In the list of layers, select only the layer Dimension. This completes the creation of the section.

To create a new section, press Add. A new tab appears in the window. Set the section parameters as described above, repeat the process for all sections. Of course, each section must have its own set of layers:

copper top - Top, Pads, Vias

copper bottom - Bottom, Pads, Vias

silkscreen on top - tPlace, tDocu, tNames

top mask - tStop

bottom mask - bStop

drilling - Drill, Holes

and the filename, for example:

top copper - %P/gerber/%N.TopCopper.grb

bottom copper - %P/gerber/%N.BottomCopper.grb

top silkscreen - %P/gerber/%N.TopSilk.grb

top mask - %P/gerber/%N.TopMask.grb

bottom mask - %P/gerber/%N.BottomMask.grb

drilling - %P/gerber/%N.Drill.xln

For a drill file, the output device ( device) should be EXCELLON, but not GERBER_RS274X

Keep in mind that some board manufacturers only accept files with names in the 8.3 format, that is, no more than 8 characters in the file name, no more than 3 characters in the extension. This should be taken into account when naming files.

We get the following:

Then open the board file ( File => Open => Board). Make sure the board file has been saved! Click Process Job- and we get a set of files that can be sent to the board manufacturer. Please note that in addition to the actual Gerber files, information files will also be generated (with extensions .gpi or .dri) - they do not need to be sent.

You can also display files only from individual sections by selecting the desired tab and pressing Process Section.

Before sending the files to the board manufacturer, it's a good idea to preview the output with a Gerber viewer. For example, ViewMate for Windows or for Linux. It can also be useful to save the board in PDF (in the board editor File->Print->PDF button) and upload this file to the manufacturer along with the gerberas. And then they are also people, this will help them not to make a mistake.

Technological operations that must be performed when working with photoresist SPF-VShch

1. Surface preparation.
a) cleaning with polished powder ("Marshalit"), size M-40, washing with water
b) decapitation with 10% sulfuric acid solution (10-20 sec), washing with water
c) drying at T=80-90 gr.C.
d) check - if within 30 seconds. a continuous film remains on the surface - the substrate is ready for use,
if not, repeat all over again.

2. Deposition of photoresist.
The photoresist is applied on a laminator with Tshafts = 80 gr.C. (See laminator operating instructions).
For this purpose, the hot substrate (after the drying cabinet) simultaneously with the film from the SPF roll is directed into the gap between the rolls, and the polyethylene (matt) film should be directed towards the copper side of the surface. After the film is pressed against the substrate, the movement of the rollers begins, while the polyethylene film is removed, and the photoresist layer is rolled onto the substrate. Mylar protective film remains on top. After that, the SPF film is cut on all sides to fit the substrate and kept at room temperature for 30 minutes. Exposure is allowed for 30 minutes to 2 days in the dark at room temperature.

3. Exposure.
Exposure through a photomask is carried out on SKCI or I-1 installations with UV lamps of the DRKT-3000 or LUF-30 type with a vacuum of 0.7-0.9 kg/cm2. The exposure time (to obtain a picture) is regulated by the installation itself and is selected experimentally. The template must be well pressed against the substrate! After exposure, the workpiece is aged for 30 minutes (up to 2 hours is allowed).

4. Manifestation.
After exposure, the process of developing the picture is carried out. For this purpose, the upper protective layer, the lavsan film, is removed from the surface of the substrate. After that, the workpiece is lowered into a solution of soda ash (2%) at T=35 gr.C. After 10 seconds, the process of removing the unexposed part of the photoresist using a foam swab begins. The time of manifestation is selected empirically.
Then the substrate is removed from the developer, washed with water, decapitated (10 sec.) with a 10% solution of H2SO4 (sulfuric acid), again with water and dried in an oven at T=60°C.
The resulting drawing should not flake off.

5. The resulting drawing.
The resulting pattern (photoresist layer) is resistant to etching in:
- ferric chloride
- hydrochloric acid
- copper sulphate
- aqua regia (after additional tanning)
and other solutions

6. Shelf life of photoresist SPF-VShch.
Shelf life of SPF-VShch is 12 months. Storage is carried out in a dark place at a temperature of 5 to 25 gr. C. in an upright position, wrapped in black paper.

Printed circuit board- this is a dielectric base, on the surface and in the volume of which conductive paths are applied in accordance with the electrical circuit. The printed circuit board is designed for mechanical fastening and electrical connection between each other by soldering the leads of electronic and electrical products installed on it.

The operations of cutting a workpiece from fiberglass, drilling holes and etching a printed circuit board to obtain current-carrying tracks, regardless of the method of drawing a pattern on a printed circuit board, are performed using the same technology.

Manual application technology
PCB tracks

Template preparation

The paper on which the PCB layout is drawn is usually thin and for more accurate drilling of holes, especially when using a handmade home-made drill, so that the drill does not lead to the side, it is required to make it denser. To do this, you need to glue the printed circuit board pattern onto thicker paper or thin thick cardboard using any glue, such as PVA or Moment.

Cutting a workpiece

A blank of foil fiberglass of a suitable size is selected, a printed circuit board template is applied to the blank and outlined around the perimeter with a marker, a soft simple pencil, or drawing a line with a sharp object.

Next, fiberglass is cut along the marked lines using metal scissors or cut with a hacksaw. Scissors cut faster and no dust. But it must be taken into account that when cutting with scissors, fiberglass is strongly bent, which somewhat worsens the strength of gluing copper foil, and if re-soldering of the elements is required, the tracks may peel off. Therefore, if the board is large and with very thin tracks, then it is better to cut it off with a hacksaw.

A printed circuit board pattern template is glued onto the cut-out blank using Moment glue, four drops of which are applied to the corners of the blank.

Since the glue sets in just a few minutes, you can immediately start drilling holes for radio components.

Hole drilling

It is best to drill holes using a special mini drilling machine with a 0.7-0.8 mm carbide drill. If a mini drilling machine is not available, then you can drill holes with a low-power drill with a simple drill. But when working with a universal hand drill, the number of broken drills will depend on the hardness of your hand. One drill is definitely not enough.

If the drill cannot be clamped, then its shank can be wrapped with several layers of paper or one layer of sandpaper. It is possible to wind tightly coil to coil of a thin metal wire on the shank.

After drilling is completed, it is checked whether all holes have been drilled. This is clearly visible if you look at the printed circuit board through the light. As you can see, there are no missing holes.

Drawing a topographic drawing

In order to protect the places of the foil on the fiberglass, which will be conductive paths, from destruction during etching, they must be covered with a mask that is resistant to dissolution in an aqueous solution. For the convenience of drawing tracks, it is better to pre-mark them with a soft, simple pencil or marker.

Before marking, it is imperative to remove traces of Moment glue, which was used to glue the printed circuit board template. Since the glue has not hardened much, it can be easily removed by rolling it with your finger. The surface of the foil must also be degreased with a rag with any agent, such as acetone or white spirit (as refined gasoline is called), and any dishwashing detergent, such as Ferry, can also be used.

After marking the tracks of the printed circuit board, you can begin to apply their pattern. Any waterproof enamel is well suited for drawing tracks, for example, alkyd enamel of the PF series, diluted to a suitable consistency with a white spirit solvent. You can draw tracks with different tools - a glass or metal drawing pen, a medical needle and even a toothpick. In this article, I will show you how to draw PCB tracks using a drawing pen and a ballerina, which are designed to be drawn on paper with ink.

Previously, there were no computers and all the drawings were drawn with simple pencils on whatman paper and then transferred with ink to tracing paper, from which copies were made using copiers.

Drawing a picture begins with contact pads, which are drawn with a ballerina. To do this, you need to adjust the gap of the sliding jaws of the drawer of the ballerina to the required line width and to set the diameter of the circle, adjust the second screw by moving the drawer from the axis of rotation.

Next, the drawer of the ballerina for a length of 5-10 mm is filled with paint with a brush. For applying a protective layer on a printed circuit board, paint of the PF or GF brand is best suited, as it dries slowly and allows you to work calmly. NC brand paint can also be used, but it is difficult to work with it, as it dries quickly. The paint should lay down well and not spread. Before drawing, the paint must be diluted to a liquid consistency, adding a suitable solvent to it little by little with vigorous stirring and trying to draw on scraps of fiberglass. To work with paint, it is most convenient to pour it into a nail polish bottle, in the twist of which a solvent-resistant brush is installed.

After adjusting the drawer of the ballerina and obtaining the required line parameters, you can begin to apply contact pads. To do this, the sharp part of the axis is inserted into the hole and the base of the ballerina is rotated in a circle.

With the correct setting of the drawing pen and the desired consistency of paint around the holes on the printed circuit board, circles of perfectly round shape are obtained. When the ballerina begins to draw poorly, the remnants of dried paint are removed from the drawer gap with a cloth and the drawer is filled with fresh paint. to outline all the holes on this printed circuit board with circles, it took only two refills of the drawing pen and no more than two minutes of time.

When the round contact pads on the board are drawn, you can start drawing conductive tracks using a manual drawing pen. The preparation and adjustment of a manual drawing pen is no different from the preparation of a ballerina.

The only thing that is additionally needed is a flat ruler, with pieces of rubber glued on one of its sides along the edges, 2.5-3 mm thick, so that the ruler does not slip during operation and the fiberglass, without touching the ruler, can freely pass under it. A wooden triangle is best suited as a ruler, it is stable and at the same time can serve as a support for the hand when drawing a printed circuit board.

So that the printed circuit board does not slip when drawing tracks, it is advisable to place it on a sheet of sandpaper, which is two sandpaper sheets riveted together with paper sides.

If, when drawing paths and circles, they touched, then no action should be taken. It is necessary to allow the paint on the printed circuit board to dry to a state where it will not stain when touched, and use the edge of a knife to remove the excess part of the pattern. In order for the paint to dry faster, the board must be placed in a warm place, for example, in winter, on a radiator. In the summer season - under the rays of the sun.

When the pattern on the printed circuit board is completely applied and all defects are corrected, you can proceed to etching it.

Printed circuit board drawing technology
using a laser printer

When printing on a laser printer, the image formed by the toner is transferred electrostatically from the photo drum, on which the laser beam painted the image, onto paper. The toner is held onto the paper, preserving the image, only due to electrostatics. To fix the toner, the paper is rolled between rollers, one of which is a thermal oven heated to a temperature of 180-220°C. The toner melts and penetrates the texture of the paper. After cooling, the toner hardens and adheres firmly to the paper. If the paper is heated again to 180-220°C, the toner will again become liquid. This property of the toner is used to transfer the image of current-carrying tracks to a printed circuit board at home.

After the file with the printed circuit board drawing is ready, it is necessary to print it using a laser printer on paper. Please note that the image of the printed circuit board drawing for this technology must be viewed from the side of the installation of parts! An inkjet printer is not suitable for these purposes, as it works on a different principle.

Preparing a paper template for transferring a pattern to a printed circuit board

If you print a printed circuit board pattern on ordinary paper for office equipment, then due to its porous structure, the toner will penetrate deeply into the body of the paper and when the toner is transferred to the printed circuit board, most of it will remain in the paper. In addition, there will be difficulties with removing paper from the printed circuit board. You will have to soak it in water for a long time. Therefore, to prepare a photomask, you need paper that does not have a porous structure, such as photographic paper, a substrate from self-adhesive films and labels, tracing paper, pages from glossy magazines.

As the paper for printing the PCB design, I use tracing paper from old stock. Tracing paper is very thin and it is impossible to print a template directly on it, it jams in the printer. To solve this problem, before printing on a piece of tracing paper of the required size, apply a drop of any glue in the corners and stick it on a sheet of A4 office paper.

This technique allows you to print a printed circuit board pattern even on the thinnest paper or film. In order for the toner thickness of the pattern to be maximum, before printing, you need to configure the “Printer Properties” by turning off the economical printing mode, and if this function is not available, then select the roughest type of paper, such as cardboard or something like that. It is quite possible that you will not get a good print the first time, and you will have to experiment a little, choosing the best print mode for a laser printer. In the resulting print of the pattern, the tracks and contact pads of the printed circuit board must be dense without gaps and smearing, since retouching at this technological stage is useless.

It remains to cut the tracing paper along the contour and the template for the manufacture of the printed circuit board will be ready and you can proceed to the next step, transferring the image to the fiberglass.

Transferring a pattern from paper to fiberglass

Transferring the PCB pattern is the most critical step. The essence of the technology is simple, paper, with the side of the printed pattern of the tracks of the printed circuit board, is applied to the copper foil of the fiberglass and pressed with great effort. Next, this sandwich is heated to a temperature of 180-220°C and then cooled to room temperature. The paper is torn off, and the pattern remains on the printed circuit board.

Some craftsmen suggest transferring a pattern from paper to a printed circuit board using an electric iron. I tried this method, but the result was unstable. It is difficult to simultaneously heat the toner to the desired temperature and evenly press the paper against the entire surface of the printed circuit board when the toner solidifies. As a result, the pattern is not completely transferred and there are gaps in the pattern of PCB tracks. It is possible that the iron did not heat up enough, although the regulator was set to the maximum heating of the iron. I did not want to open the iron and reconfigure the thermostat. Therefore, I used another technology that is less laborious and provides a 100% result.

On a printed circuit board cut to size and degreased with acetone, a blank of foil fiberglass was glued to the corners of a tracing paper with a pattern printed on it. On top of the tracing paper put, for a more uniform pressure, heels of sheets of office paper. The resulting package was placed on a sheet of plywood and covered with a sheet of the same size on top. This whole sandwich was clamped with maximum force in the clamps.

It remains to heat the made sandwich to a temperature of 200 ° C and cool. An electric oven with a temperature controller is ideal for heating. It is enough to place the created structure in a cabinet, wait for the set temperature to reach, and after half an hour remove the board for cooling.

If an electric oven is not available, then you can also use a gas oven by adjusting the temperature with the gas supply knob according to the built-in thermometer. If there is no thermometer or it is faulty, then women can help, the position of the regulator knob, at which pies are baked, will do.

Since the ends of the plywood were warped, just in case, I clamped them with additional clamps. to avoid this phenomenon, it is better to clamp the printed circuit board between metal sheets 5-6 mm thick. You can drill holes in their corners and clamp the printed circuit boards, tighten the plates with screws and nuts. M10 will be enough.

After half an hour, the design has cooled down enough for the toner to harden, the board can be removed. At the first glance at the removed printed circuit board, it becomes clear that the toner transferred from the tracing paper to the board perfectly. The tracing paper fit snugly and evenly along the lines of the printed tracks, the rings of the pads and the marking letters.

The tracing paper easily came off almost all tracks of the printed circuit board, the remains of the tracing paper were removed with a damp cloth. But still, there were gaps in several places on the printed tracks. This can happen as a result of uneven printing of the printer or remaining dirt or corrosion on the fiberglass foil. Gaps can be filled with any waterproof paint, nail polish or retouched with a marker.

To check the suitability of a marker for retouching a printed circuit board, you need to draw lines on paper with it and moisten the paper with water. If the lines do not blur, then the retouching marker is suitable.

Etching a printed circuit board at home is best in a solution of ferric chloride or hydrogen peroxide with citric acid. After etching, the toner from the printed tracks is easily removed with a swab dipped in acetone.

Then holes are drilled, conductive paths and contact pads are tinned, and radioelements are soldered.

This form was taken by a printed circuit board with radio components installed on it. The result was a power supply and switching unit for an electronic system that complements an ordinary toilet bowl with a bidet function.

PCB etching

To remove copper foil from unprotected areas of foil fiberglass in the manufacture of printed circuit boards at home, radio amateurs usually use a chemical method. The printed circuit board is placed in an etching solution and, due to a chemical reaction, the copper, unprotected by the mask, dissolves.

Etching solution recipes

Depending on the availability of components, radio amateurs use one of the solutions shown in the table below. Etching solutions are listed in order of popularity for their use by radio amateurs in the home.

Solution name	Compound	Quantity	Cooking technology	Advantages	disadvantages
Hydrogen peroxide plus citric acid	Hydrogen peroxide (H 2 O 2)	100 ml	Dissolve citric acid and table salt in a 3% hydrogen peroxide solution	Availability of components, high pickling rate, safety	Not stored
	Citric acid (C 6 H 8 O 7)	30 g
	Salt (NaCl)	5 g
Aqueous solution of ferric chloride	Water (H2O)	300 ml	Dissolve ferric chloride in warm water	Sufficient etching rate, reusable	Low availability of ferric chloride
	Ferric chloride (FeCl 3)	100 g
Hydrogen peroxide plus hydrochloric acid	Hydrogen peroxide (H 2 O 2)	200 ml	Pour 10% hydrochloric acid into a 3% hydrogen peroxide solution	High pickling rate, reusable	Requires high precision
	Hydrochloric acid (HCl)	200 ml
Aqueous solution of copper sulphate	Water (H2O)	500 ml	In hot water (50-80 ° C), dissolve table salt, and then blue vitriol	Component Availability	The toxicity of copper sulfate and slow etching, up to 4 hours
	Copper sulfate (CuSO 4)	50 g
	Salt (NaCl)	100 g

Etch printed circuit boards in metal utensils are not allowed. To do this, use a container made of glass, ceramic or plastic. It is allowed to dispose of the spent pickling solution into the sewer.

Etching solution of hydrogen peroxide and citric acid

A solution based on hydrogen peroxide with citric acid dissolved in it is the safest, most affordable and fastest working. Of all the listed solutions, by all criteria, this is the best.

Hydrogen peroxide can be purchased at any pharmacy. Sold in the form of a liquid 3% solution or tablets called hydroperite. To obtain a liquid 3% solution of hydrogen peroxide from hydroperite, you need to dissolve 6 tablets weighing 1.5 grams in 100 ml of water.

Citric acid in the form of crystals is sold in any grocery store, packaged in bags weighing 30 or 50 grams. Table salt can be found in any home. 100 ml of pickling solution is enough to remove 35 µm thick copper foil from a 100 cm2 printed circuit board. The spent solution is not stored and cannot be reused. By the way, citric acid can be replaced with acetic acid, but because of its pungent smell, you will have to pickle the printed circuit board in the open air.

Pickling solution based on ferric chloride

The second most popular pickling solution is an aqueous solution of ferric chloride. Previously, it was the most popular, since ferric chloride was easy to get at any industrial enterprise.

The etching solution is not picky about the temperature, it etchs rather quickly, but the etching rate decreases as the ferric chloride in the solution is consumed.

Ferric chloride is very hygroscopic and therefore quickly absorbs water from the air. As a result, a yellow liquid appears at the bottom of the jar. This does not affect the quality of the component and such ferric chloride is suitable for the preparation of an etching solution.

If the used solution of ferric chloride is stored in an airtight container, then it can be used repeatedly. To be regenerated, it is enough to pour iron nails into the solution (they will immediately be covered with a loose layer of copper). Leaves hard-to-remove yellow spots upon contact with any surface. At present, a solution of ferric chloride for the manufacture of printed circuit boards is used less frequently due to its high cost.

Etching solution based on hydrogen peroxide and hydrochloric acid

Excellent pickling solution, provides high pickling speed. Hydrochloric acid, with vigorous stirring, is poured into a 3% aqueous solution of hydrogen peroxide in a thin stream. Pouring hydrogen peroxide into acid is unacceptable! But due to the presence of hydrochloric acid in the etching solution, great care must be taken when etching the board, since the solution corrodes the skin of the hands and spoils everything it gets on. For this reason, an etching solution with hydrochloric acid at home is not recommended.

Etching solution based on copper sulphate

The method of manufacturing printed circuit boards using copper sulphate is usually used if it is impossible to manufacture an etching solution based on other components due to their unavailability. Copper sulfate is a pesticide and is widely used for pest control in agriculture. In addition, the PCB etching time is up to 4 hours, while it is necessary to maintain the temperature of the solution at 50-80°C and ensure that the solution is constantly changed at the etched surface.

PCB etching technology

For etching the board in any of the above etching solutions, glass, ceramic or plastic utensils, such as dairy products, are suitable. If there was no suitable container size at hand, then you can take any box made of thick paper or cardboard of a suitable size and line its inside with plastic wrap. An etching solution is poured into the container and a printed circuit board is carefully placed on its surface with a pattern down. Due to the forces of the surface tension of the liquid and the low weight, the board will float.

For convenience, a cork from a plastic bottle can be glued to the center of the board with glue. The cork will simultaneously serve as a handle and a float. But there is a danger that air bubbles form on the board and in these places the copper will not corrode.

To ensure uniform etching of copper, you can put the printed circuit board on the bottom of the tank with the pattern up and periodically shake the bath with your hand. After a while, depending on the pickling solution, areas without copper will begin to appear, and then the copper will completely dissolve on the entire surface of the printed circuit board.

After the final dissolution of copper in the pickling solution, the printed circuit board is removed from the bath and thoroughly washed under running water. The toner is removed from the tracks with a rag soaked in acetone, and the paint is well removed with a rag soaked in a solvent that was added to the paint to obtain the desired consistency.

Preparing the printed circuit board for the installation of radio components

The next step is to prepare the printed circuit board for the installation of radio elements. After removing the paint from the board, the tracks must be processed in a circular motion with fine sandpaper. You don’t need to get carried away, because the copper tracks are thin and can be easily grinded off. Just a few passes with a low-pressure abrasive is sufficient.

Further, the current-carrying tracks and contact pads of the printed circuit board are covered with an alcohol-rosin flux and tinned with soft solder with an electric soldering iron. so that the holes on the printed circuit board are not tightened with solder, you need to take a little of it on the soldering iron tip.

After completing the manufacture of the printed circuit board, all that remains is to insert the radio components into the intended positions and solder their leads to the sites. Before soldering, the legs of the parts must be moistened with alcohol-rosin flux. If the legs of the radio components are long, then they must be cut with side cutters before soldering to a protrusion length of 1-1.5 mm above the surface of the printed circuit board. After completing the installation of the parts, it is necessary to remove the remains of rosin using any solvent - alcohol, white spirit or acetone. They all successfully dissolve rosin.

It took no more than five hours to implement this simple capacitive relay circuit from the PCB traces to the production of a working sample, much less than the layout of this page.