PCB at home. PCB manufacturing
In the manufacture printed circuit boards at home, the simplest and most common method is the LUT method.
This method is not without drawbacks. If the toner is heated weakly, then it will not stick to the printed circuit board foil, if heated strongly, it will be smeared. It is necessary to select the print quality, if there is a lot of toner, it will be smeared, the tracks, at small intervals, may stick together. It is bad to warm up the printed board, and some of the tracks will not be printed, especially this often happens in the corners of printed circuit boards.
I will tell you about a method for transferring a printed pattern to foil without heating. The drawing will not be smeared, all the toner is transferred from the paper. To do this, you need two cheap chemical components: alcohol and acetone.
Instead of acetone, you can use any other substance that dissolves the toner well.
Alcohol does not react with toner, anyone who has tried to scrub a PCB with it after etching knows this, but it quickly disappears. It is needed in order to dilute the acetone.
Acetone dissolves toner very well and also evaporates quickly. If you try to use it in its pure form, it will smear your drawing, as in the photo.
There will be some kind of mess on the printed circuit board.
In what proportions should acetone and alcohol be mixed?
It will take three parts of acetone and eight parts of alcohol. All this must be mixed and poured into a container with a tight lid. It is important that the container does not dissolve with acetone.
How to use the mixture?
Draw a little of the resulting mixture into a syringe,
Apply it to the future printed circuit board, previously cleaned of oxides and well degreased (this is important) (not on a printout). After that, put your printout on it. You can especially take your time, the mixture does not disappear instantly. Lightly press the paper so that it is completely attached to the board and soaked with the solution,
Wait 10-15 seconds, you will see when the paper is saturated,
After that, press the paper firmly, press the paper strictly perpendicular so that it does not move. Wait another 10-20 seconds. During this time, the toner will react with acetone, become sticky and stick to the board. Blot the remaining liquid with paper towels, wait until the paper dries, then dip the board in water so that the paper gets wet, and peel it off. All the toner will remain on the board, and the paper will be clean. After that, rinse the board from the remnants of acetone. Everything. You can etch the printed circuit board.
In the photo, I removed the paper without soaking it in water and the toner remained in places.
Being in amateur radio for many years I made printed circuit boards different ways. I painted with varnish (remember those times), with a cutter (simple boards), etc. IN Lately the "Laser printer and iron" method is popular for transferring a pattern onto a foil fiberglass. According to various recommendations and articles on the Internet, I tested almost all the materials that were recommended. Thin glossy paper from magazines, photo paper, fax paper, backing paper from self-adhesive film, and even thermal transfer paper for fabric. I’m lying, I haven’t tested food aluminum foil.
None of the methods satisfied me because the result was not stable (it could have happened the first time only from the third or fifth). The best results were obtained on photographic paper. Worse on fax and on sheets from magazines, and besides, after "rolling" with an iron, it had to be soaked. Strongly it does not bother in time, but still (10 minutes on average). On paper for thermal transfer to fabric, it turned out well, but to remove the substrate, isopropyl alcohol was required, and the temperature of the iron also had to be set very accurately. A little mistake - all marriage. On substrates from a self-adhesive film, the toner fell off the polished surface during printing (I don’t know what filth they are covered with)
All with the introduction is over - let's get started ...
Oddly enough, but let's get back to the substrates from the self-adhesive film (self-adhesive wallpaper). Basically, the technology is largely identical to that previously described in different sources. It's all about the material
What we need:
1. Foil textolite (one-two-sided, as you need)
2. Laser printer (I have HP1020 at home)
3. Iron - any
4. Silit-Banks - for cleaning the surface of the board
5. Ferric chloride for etching the board (I did not check with other compositions such as "copper sulfate-salt", etc.)
6. Thin drill bits for drilling (this is understandable)
7. SELF-ADHESIVE FILM
Let's take a closer look at point 7.
We go to the bazaar or to a store where they sell wallpaper and look for cheap Chinese film. If you look at the substrate on which the film lies, you can see a mesh pattern with letters and numbers (each brand is different). So, we are interested in a film on the substrate of which there are large numbers 333
.WE ARE INTERESTED IN SHE AND ONLY SHE. We have a roll of 10 meters 50 cm wide. It costs 100 rubles. There are also 777, 555, 556, etc. but we don't need it.
Here is a picture of the background
More like always. We cut out (to whom it is more convenient and more convenient) a piece of textolite of the desired size with a margin of 1 cm from each edge. At these places, you can then drill holes to match the two layers (if you are making a double-sided board). We clean the board from dirt. I do not rub with a "null sandpaper", but I use Silit-Banks (see ads on TV). Pour a little Silite on the surface of the board and wait. If the surface is not very dirty and not strongly oxidized, then 1 minute is enough. The board becomes clean and pink before our eyes. If it is very dirty, then we wait longer or repeat the procedure several times. We wash the board with water and carry it to dry. Do not take the board where we will transfer the drawing with our fingers, but if you have taken it, then there is nothing terrible, just wipe it with a swab dipped in acetone before transferring
"Komet" is also good for cleaning (see ads on TV), but in powder.
Here is the finished board
While the board is drying, we print the pattern. I draw and print on SprintLayout 4.0. Everyone has their own preferences. Use what you like best.
We cut out a piece of the film (we do not tear off the film itself yet) of the desired size. Since the liner is very thin after peeling off the film, the printer will chew on it. Trust me - it will. Therefore, we paste it on a sheet of ordinary office paper. It is necessary to glue it so that after removing the film, a polished surface of the substrate remains on top. I use a few drops of Moment glue in the corners of the substrate and in the center of the long sides.
Everything is ready for printing. We tear off the film.
Insert the sandwich into the printer and print. In the printer settings, do not forget to set the maximum toner. Do you understand what I'm talking about.
Printed? Let's see how it is with the drawing. It was on this type of film, or rather the 333 substrate, that the toner stopped falling off for me, it fell on others - dear mother ...
We turn on the iron (if it has not been turned on before) The temperature can be checked like this. We print on ordinary paper, put the toner up on an inverted iron and look. The toner is shiny - everything is fine, the temperature is enough to melt.
I didn’t set it up at all, I just set it to the maximum and that’s it.
We put plywood (10mm) on the table, then we don’t need a book or a newsprint magazine (remember, there were such) on the book board with foil up
We make a tampon from a bandage or a thin clean rag. You can see it in the picture on the right.
We DO NOT PUT a substrate with a pattern - how.
We cover it with a sheet of A4 office paper and put the iron. If the board is larger than the surface of the sole of the iron, then iron the board 30-40 seconds are enough for the board to warm up
Again cover it with a sheet of A4 office paper and put the iron on and start ironing. There is practically no need to press, we just reheat the board (it has already cooled down a bit). Here already 15-20 seconds is enough, although I held more. We remove a sheet of office paper.
Quickly, for 20-30 seconds, we spread the entire surface with a swab from a rag, especially along the edges of the board. We rub both along and across - the paths are not drawn in one direction. Here you need to press a little, as if rubbing over the surface.
Note: those who are afraid for their fingers can put on gloves from their cotton fabric - the board is hot.
That's all, we wait until the board cools down, so that it can be safely picked up.
We grab the tip of the substrate and gently tear it off the board. She practically leaves on her own.
And here is the drawing translated
We look that everything is wonderful - we rejoice!
I personally repeated it myself 20 times, and nothing has ever fallen off. 100% translation result. (okay persuaded 99%)
Tracks 0.2 turned out to be flying.
Here is the finished board without drilling - I'm already going to bed at night. Tomorrow we will drill
I apologize for the last shot, the camera is not mine and you can see how it shoots shiny surfaces. Believe me everything is OK.
Then everything is as usual.
We poison. Drilling. Ludim. Cut to desired size. soldering
If everything is prepared (printed circuit board drawing, all materials), the whole process takes me 20-25 minutes along with board etching
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 very difficult for the inexperienced, then I will gladly share my proven technology, which allows you to get the first time and without any strain, printed circuit boards with tracks 0.3mm and clearance between them up to 0.2mm. As an example, I will make a debug board for my training course dedicated to the controller 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 will need laser printer Fortunately, they are now not uncommon. 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 maximum density and toner contrast, be sure to turn off 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 main subtlety technology LUT because of which many have problems with the exit quality boards and they drop it. Through many experiments, it was found that the most best result achieved when printing on glossy photo paper for inkjet printers. 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 oven. 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 is better for testing to print on plain paper 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. Cut out a piece right size, without permits 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 outer surface 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 places need to be painted. 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 jerseys or Gucci felt boots away 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 a large number 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 gaps, then the toner lay crookedly 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 moron 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?
Any electronic device requires connecting together a bunch of parts. Of course, you can solder the device on the circuit board, but at the same time there is a high risk of making a bunch of mistakes, and the device itself will look very dumb. Wires sticking out in all directions will be appreciated only by lovers of trash design. Therefore, we will make a printed circuit board!
And to make it easier for you, I made a video lesson on the topic of manufacturing printed circuit boards using the method laser iron aka LUT.
A full cycle, from preparing the board from a piece of textolite, to drilling and tinning.
Printed circuit boards are made of foil insulating material (getinax, fiberglass, fluoroplast). A metal foil is firmly glued to one of the sides of the sheet of insulating material, which makes it possible to obtain printed conductors of any shape in the future. They are a strip of foil connecting the leads of two or more parts mounted on a printed circuit board in accordance with circuit diagram radio engineering device.
What is required for the manufacture of printed circuit boards?
0) Drawing of the printed circuit board in electronic form.
1) Laser printer for printing an imprint of the future board. It is desirable that the printer has the possibility of a direct path - printing with minimal paper bending. I have Samsung ML1520. Print to the maximum, without any toner saving!
2) Foil textolite.
3) Photo paper for inkjet printing Lomond 120g/m glossy, one-sided with improved coverage. Also good results on Lomond 230g/m glossy paper.
4) Brush for suede with metal + plastic pile (optional)
5) Acetone
6) Nulevka skin
The shape of the conductors, their number and mutual arrangement are determined by the device diagram, the elements used, as well as the experience of a radio amateur developing a printed circuit board drawing.
It must be remembered that the drawings are developed for the installation of well-defined types of elements. If the types of some elements are different (for example, instead of capacitors of the K50-6 type, capacitors of the K53-4 type with a different pin arrangement are used), then the board drawing will have to be changed accordingly.
Most often, radio amateurs use foil fiberglass of the STF brand or foil getinaks of the GF brand for the manufacture of a printed circuit board. Getinaks in comparison with fiberglass has slightly worse characteristics, but it is quite suitable for the vast majority of amateur radio structures. When working with getinax, use fusible solders (POSK-50, POS-40, POS-61), since the foil can easily peel off when the printed conductors overheat during soldering.
Foil materials produced by industry have different thickness. Typically, a material with a thickness of 1.5 mm is used. But in cases where the fee large sizes and it is necessary to install massive elements on it, use a material with a thickness of 2-2.5 mm.
If you do not have ready-made foil material at your disposal, you can make it yourself.
Cut out a workpiece from a getinax 1.5-2 mm thick to fit the future board, and from a sheet of copper foil (its thickness should be in the range of 0.05-0.1 mm) - a plate of the same size. Sand the surfaces to be bonded with fine-grained sandpaper, clean them from dust and degrease with acetone or gasoline. Apply a current layer of BF-2 glue to the getinax and foil and dry it for an hour at room temperature, then apply a second layer of glue and dry for about 30 minutes. After that, put the foil on the getinax and roll it with a hard roller from the middle to the edges. Place the workpiece processed in this way under a press or in a vise and hold for 2-3 days.
Place the workpiece between two metal plates (lay additional cardboard on the side of the foil) and firmly squeeze the entire package.
Drawing a printed circuit board
Prepare an auxiliary drawing of the printed circuit board from the side of the printed conductors on a scale of 1: 1, mark the centers of the future holes with dots.
Glue the design to the foil with a few drops of rubber glue. With the help of a center punch, with light blows of a small hammer, alternately transfer the centers of all future holes to the foil,
Keep the punch perpendicular to the surface of the board, otherwise the marking will be inaccurate. Before this operation, do not sand the foil so that the marks left by the center punch are more noticeable.
Remove the drawing from the workpiece and drill holes. The best thing to do is to drilling machine, since the holes for the outputs of parts have 0 0.8 -1 mm. You can also use an electric drill. To do this, clamp the workpiece in a vise through cardboard or getinax spacers with foil towards you. Sitting on a chair, place the elbow of your left hand on a workbench, place an electric drill in your palm, and right hand hold the drill by the handle.
Adjust the drill feed in the horizontal plane with the coordinated movements of both hands. As you drill holes, change the position of the workpiece, at the end of the work, check whether all the holes have been drilled.
Sand the foil with fine sandpaper, remove dust and residues of rubber glue, degrease the surface with acetone. Now try not to touch the foil with your hands until the end of the processing of the printed circuit board.
In order for printed conductors to remain on the board after etching, paint over the corresponding sections of the foil with some kind of acid-resistant varnish or paint. Most often, radio amateurs use nitro enamel; it dries quickly and adheres well to the surface of the foil. For ease of use, the paint should be poured in small portions into small glass or metal dishes and collected from there. You can transfer an image from paper to foil using. a conventional or glass drawing pen, a modified medical syringe, a fountain pen rod from which the ball has been removed, or an ordinary pointed match. It is desirable that the holes are also covered with paint, this will protect their walls from impregnation with solutions during etching. As soon as stretching “threads” appear on the match, change the portion of the paint, otherwise they can form the thinnest jumpers between the conductors on the board, which will make the device impossible to work.
To transfer the picture, you can also use asphalt-bitumen varnish, colored zaponlak, BF glue, some types of ink and ink.
After all the conductors are shown, check the quality of the drawing, correct the appearance of the “conductors” if necessary, remove the jumpers, work out the gaps between the contact pads (they must be at least 1 mm). When examining the drawing, it is advisable to use a magnifying glass.
Some radio amateurs use instead of paint or varnish sticky tape- adhesive tape, cutting “conductors” and “contact pads” from it and sticking them on the foil in accordance with the figure. For those who want to use this method of preparing the board for etching, we advise you to carefully monitor the quality of the tape segments, otherwise there may be gaps in the conductors. More high quality drawing can be obtained using special devices for drawing. You can get acquainted with the description of the design of one of them by reading the book by Yu. V. Bezdelev “Flat and volumetric modules in amateur designs” (published by the Energia publishing house in 1977).
Remove parts of the foil not protected by paint, varnish or adhesive tape by etching the board in one of the recommended solutions. The main material for etching is a solution of ferric chloride - it is sold in chemical stores in powder or granules. To obtain a solution, pour about 3/4 of ferric chloride powder into a glass and add warm water.
Board etching
For etching, use a glass or plastic container, such as a photographic cuvette. Put the board into the solution with the pattern up, the entire surface of the board should be filled with the solution. The etching process is accelerated if the vessel is shaken or heated. Pickling produces poisonous fumes, so work either in a well-ventilated area or outdoors. Periodically check the condition of the board by lifting it up for inspection with wooden or plastic sticks, metal tools and devices for this purpose cannot be used. After making sure that the foil in exposed areas has completely disappeared, stop the etching process,
Transfer, for example, using a clothespin, the board under running water and rinse thoroughly, then dry it at room temperature.
If you are going to reuse the solution, pour it into a tightly sealed container and store in a cool, dark place. Please note that the effectiveness of the solution decreases with repeated use.
When working with a solution of ferric chloride, remember that it should not get on hands and other exposed parts of the body, as well as on the surfaces of bathtubs and sinks, since yellow spots that are difficult to wash off may remain on the latter.
A solution of ferric chloride can be made independently by treating iron filings with hydrochloric acid. Take 25 parts by weight of 10% hydrochloric acid and mix with one part by weight of iron filings. Keep the mixture in a tightly closed container for 5 days in a dark place, after which it can be used. When pouring the solution into the etching vessel, do not shake it: the precipitate should remain in the vessel in which the solution was prepared.
The duration of the process of etching the board in a solution of ferric chloride depends on the concentration of the solution, its temperature, the thickness of the foil and is usually 40 - 50 minutes.
Solutions for board etching can be prepared not only on the basis of ferric chloride. May be more affordable for many radio amateurs water solution blue vitriol And table salt. It is easy to prepare - dissolve in 500 ml hot water(t about 80 ° C) 4 tablespoons of table salt and 2 tablespoons of copper sulfate crushed into powder. If the solution is applied immediately, its effectiveness will be low, it increases significantly after the solution has been aged for two to three weeks.
The board etching time in such a solution is three hours or more.
A significant reduction in etching time can be achieved using acid-based solutions. Board etching process, e.g. in a concentrated solution nitric acid lasts only 5-7 minutes.
In this case, the drawing is applied with a medium-viscosity bakelite varnish using a glass drawing pen and a fountain pen with the ball removed. When filling the tool, lower its working end into the varnish, and create a vacuum from the other end by sucking air through a PVC tube. After etching, wash the board thoroughly with soap and water.
Good results are obtained by using a solution of hydrochloric acid and hydrogen peroxide. To prepare, take 20 parts (by volume) of hydrochloric acid with a density of 1.19 g / cm3, 4 parts of pharmacy hydrogen peroxide, 40 parts of water. First, mix water with hydrogen peroxide, then carefully add acid. The drawing in this case is done with nitro paint.
Pour acid-based solutions into a glass or ceramic dishes, work with them only in well-ventilated areas.
The method of galvanic etching of boards
This will require a direct current source with a voltage of 25-30 V and a concentrated solution of common salt. Using an alligator clip, connect the positive pole of the source to the unpainted areas of the board foil, and attach a cotton swab to the bare and coiled end of the wire coming from the negative pole of the source. Soak the latter abundantly with a salt solution and, lightly pressing it against the foil, move it over the surface of the board, the movement of the swab should resemble the drawing of the number 8. The foil will, as it were, “wash off”. Change the tampon as it gets dirty.
In all cases, after the end of the etching process, the boards are thoroughly washed in running water(for example, under a water tap, dry and only then remove the paint with acetone, white spirit and other similar solvents. The paint remaining in the holes is removed with a thin awl or needle.
Now clean the conductors to a shine with the finest sandpaper or ink eraser, remove all foreign particles from the board and tin the conductors in the following way: lubricate them with an alcohol-rosin flux (15% rosin and 15% ethyl alcohol), take a piece of braid from a shielded cable and impregnate it with the same flux, put a little POS-61 solder on the soldering iron tip and “rub” the solder into the foil through the braid. The speed of the soldering iron should be such that the conductors are well tinned, but do not peel off the board material. When performing this work, it is desirable to fix the board motionless. You can limit yourself to tinning only contact pads.
Having finished tinning the conductors, remove the flux residues and excess solder (including from the holes), check the quality of the board workmanship and proceed with the installation of radio elements on it.
In this note, I will analyze the popular ways to create printed circuit boards on your own at home: LUT, photoresist, hand drawing. And also with the help of what programs it is best to draw PP.
Once upon a time, electronic devices were mounted using surface mounting. Now only tube audio amplifiers are assembled this way. Printed wiring is in mass circulation, which has long turned into a real industry with its own tricks, features and technologies. And there are a lot of tricks. Especially when creating software for high-frequency devices. (I think I will somehow review the literature and the design features of the location of the PCB conductors)
The general principle of creating printed circuit boards (PCB) is to apply tracks on the surface of a non-conductive material that conduct this very current. The tracks connect the radio components according to the required scheme. The output is electronic device, which can be shaken, worn, sometimes even wetted without fear of damaging it.
IN in general terms the technology for creating a printed circuit board at home consists of several steps:
- Choose a suitable foil fiberglass. Why textolite? It's easier to get it. Yes, and it's cheaper. Often this is enough for an amateur device.
- Apply a printed circuit board pattern to the textolite
- Bleed off excess foil. Those. remove excess foil from areas of the board that do not have a pattern of conductors.
- Drill holes for component leads. If you need to drill holes for components with leads. For chip components, this is obviously not required.
- Tin the conductive tracks
- Apply solder mask. Optional if you want to bring your board closer to the factory ones.
Another option is to simply order your board from the factory. Now many companies provide services for the production of printed circuit boards. You will get an excellent factory printed circuit board. They will differ from the amateur one not only in the presence of a solder mask, but also in many other parameters. For example, if you have a double-sided PCB, then there will be metallization of holes on the board. You can choose the color of the solder mask, etc. The advantages of the sea, just have time to slobber money!
Step 0
Before making PP, it must be drawn somewhere. You can draw it on graph paper in the old fashioned way and then transfer the drawing to the workpiece. Or you can use one of the many programs for creating printed circuit boards. These programs are called the common word CAD (CAD). Of those available to a radio amateur, one can name DeepTrace (free version), Sprint Layout, Eagle (of course, you can also find specialized ones like Altium Designer)
With the help of these programs, you can not only draw the PCB, but also prepare it for production in the factory. Suddenly you want to order a dozen scarves? And if you don’t want to, then it’s convenient to print out such a PP and make it yourself using LUT or photoresist. But more on that below.
Step 1
So, the workpiece for PCB can be conditionally divided into two parts: a non-conductive base and a conductive coating.
Blanks for PP are different, but most often they differ in the material of the non-conductive layer. You can find such a substrate made of getinax, fiberglass, a flexible base of polymers, compositions of cellulose paper and fiberglass with epoxy resin, even metal base happens. All these materials differ in their physical and mechanical properties. And in production, the material for PP is selected based on economic considerations and technical conditions.
For home PCBs, I recommend foil fiberglass. Easy to get and reasonable price. Getinaks are probably cheaper, but personally I can't stand them. If you dismantled at least one massive Chinese device, then you probably saw what the software is made of? They are brittle, and stink when soldered. Let the Chinese smell it.
Depending on the device being assembled and its operating conditions, you can choose the appropriate textolite: single-sided, double-sided, with different thickness foil (18 µm, 35 µm, etc. etc.
Step 2
To apply a PP pattern on a foil base, radio amateurs have worked out many methods. Among them, the two most popular in present time: LUT and photoresist. LUT is short for "laser iron technology". As the name suggests, you will need a laser printer, an iron, and glossy photo paper.
LUT
A picture is printed on photo paper in a mirrored form. Then it is superimposed on the foil textolite. And it warms up nicely. The heat causes the toner from the glossy photo paper to adhere to the copper foil. After warming up, the board is soaked in water and the paper is carefully removed.
In the photo above, just the board after etching. The black color of the current-carrying tracks is due to the fact that they are still covered with hardened toner from the printer.
Photoresist
This is a more sophisticated technology. But you can also get a better result with it: without mordant, thinner paths, etc. The process is similar to LUT, but the PP pattern is printed on transparent film. This results in a template that can be reused multiple times. Then a "photoresist" is applied to the textolite - a film or liquid sensitive to ultraviolet (the photoresist can be different).
Then, a photomask with a PP pattern is firmly fixed on top of the photoresist, and then this sandwich is irradiated with an ultraviolet lamp for a clearly measured time. I must say that the PP pattern on the photomask is printed inverted: the tracks are transparent, and the voids are dark. This is done so that when the photoresist is illuminated, the areas of the photoresist that are not covered by the template react to ultraviolet and become insoluble.
After exposure (or exposure, as the experts call it), the board "appears" - the illuminated areas become dark, the unexposed areas become light, since the photoresist simply dissolved in the developer (ordinary soda ash). Then the board is etched in a solution, and then the photoresist is removed, for example, with acetone.
Types of photoresist
There are several types of photoresist in nature: liquid, self-adhesive film, positive, negative. What is the difference and how to choose the right one for you? In my opinion, in amateur use there is not much difference. Here, as you get the hang of it, you will apply that kind. I would single out only two main criteria: the price and how convenient it is for me personally to use this or that photoresist.
Step 3
Etching of a printed PP blank. There are many ways to dissolve the unprotected part of the foil with PP: etching in ammonium persulfate, ferric chloride,. I like last way: fast, clean, cheap.
We place the workpiece in the etching solution, wait 10 minutes, take it out, wash it, clean the tracks on the board and proceed to the next step.
Step 4
The board can be tinned with either Rose or Wood alloy, or simply cover the tracks with flux and walk along them with a soldering iron. Rose and Wood alloys are multicomponent fusible alloys. Wood's alloy also contains cadmium. So at home, such work should be carried out under a hood with a filter. It is ideal to have a simple smoke extractor. Do you want to live happily ever after? :)
Step 6
I will skip the fifth step, everything is clear there. But applying a solder mask is quite interesting and not the easiest step. So let's study it in more detail.
The solder mask is used in the process of creating PCB in order to protect the tracks of the board from oxidation, moisture, flux during the installation of components, and also to facilitate the installation itself. Especially when SMD components are used.
Usually, in order to protect the PCB tracks without a mask from chem. and fur effects seasoned radio amateurs cover such tracks with a layer of solder. After tinning, such a board often looks somehow not very beautiful. But it is worse that in the process of tinning, you can overheat the tracks or hang "snot" between them. In the first case, the conductor will fall off, and in the second case, such unexpected "snot" will have to be removed in order to eliminate short circuit. Another disadvantage is the increase in capacitance between such conductors.
First of all: soldermask is quite toxic. All work should be carried out in a well-ventilated area (preferably under a hood), and avoid getting the mask on the skin, mucous membranes and eyes.
I can’t say that the process of applying the mask is quite complicated, but it still requires a large number steps. After deliberation, I decided that I would give a link to more or less detailed description applying a solder mask, since there is no way to demonstrate the process yourself right now.
Create, guys, it's interesting =) Creating PP in our time is not just a craft, but a whole art!