Manufacturing of boards using the loot method. We make printed circuit boards ourselves

This video lesson shows the implementation of LUT technology, which is used to make a double-sided printed circuit board. At home you can make compact ones using SMD elements. Here, using the example of a charger for a 18650 lithium-ion battery taken from an old laptop battery, we will go through the process of creating a board from printing a drawing to turning it on.

Watch the compressedvideo channel video

First of all, we draw a printed circuit board in the Eagle program for its subsequent manufacturing using laser-iron technology. About high-power lasers. The program is free for one- and two-sided applications. We upload each side of the signet in black and white into a graphic editor and combine them to print on one sheet. We will print on tracing paper. But to prevent the printer from jamming it, you will need glue and an A4 sheet. We buy 40 sheets of tracing paper at the nearest stationery store.

First, look for the smooth side. We take out a sheet of paper and check where it slides more than usual, this is the top side. Now we bend the sheet of paper so that we can insert tracing paper. 1-1.5 cm is enough. We do not coat it too much with glue, as it will go inside the printer, and we glue the tracing paper evenly. If you make it crooked, the two sides won't match.

Preparing a “sandwich”. Now we fold the sheet at the top to place it in a manual feed printer. Insert with tracing paper facing up. We get a fingerprint. We cut out a large piece and fold it along the fold, aligning the two sides of the board to the light. Tracing paper is ideal for this. All holes are visible and can be accurately aligned. We glue the sheet together to make a pocket, and we will place the board in it. To do this, coat it with glue on both sides.

Preparing a board for implementing LUT technology

To prepare the board we will need cleaning powder. If it says it cleans copper, that's it. You can take another one, or even paste. GOI (but not sandpaper). We take the powder and begin to clean the board until it reaches a mirror shine. Once there are no dark spots left on the board, it can be placed in the pocket. Once cleaned, you can only pick it up by the edges so as not to leave greasy fingerprints.

We place the board in the finished pocket and align it so that the entire print falls on it. Everything is ready for ironing. It is better to take a simple one without steam. Temperature at maximum. We carefully begin to iron over the entire area. The tracing paper sticks to the board and you can clearly see how the toner darkens. You don’t have to press too hard, but you need to iron both sides. Gradually the toner darkens and begins to bleed through the tracing paper. Once this has happened, everything is ready for the next operation. It is important not to overdo it, because the toner may spread and bottlenecks between the tracks may be flooded and will have to be cleaned up.

Now the tracing paper needs to be washed off. The toner will remain on the board, the paper will gradually come off. We cut it so that it all fits in the bath. We take ordinary water and throw the board there. We wait until it gets wet. After some time, the tracing paper begins to bubble and can be carefully removed. When wet, it comes off the board easily. The toner remains, covering all areas that we need to leave unetched. The tracing paper curls into lumps and gets wet. As a result, we get a beautiful, almost factory board.

It looks like it’s ready, but let’s take a magnifying glass and check how it turned out. It is clearly visible that there are pieces of paper left. The board will not be etched in these places. You need to remove the paper between the tracks. To do this we use a bristle brush. Moving along the paths, so as not to damage them, remove the remaining paper. When the board is dry, the places where the tracing paper remains are clearly visible, but this is not critical here. We drill a couple of holes on the side to insert the wire. She will help hold the board while we poison. We use ammonium persulfate. This is a rather aggressive substance and it is not recommended to dip your fingers in it. We take hot water from the tap. We dose it like this: one tablespoon of water per one teaspoon without a slide of persulfate. 5 spoons are enough for such a board. A water bath is also needed, since the etching reaction actively cools the solution.

Stir with a plastic or glass rod. And remember that if the solution gets on your clothes, it will leave holes. Place the board in the solution and stir for about five minutes. At first the solution is transparent, then gradually turns blue. This copper goes into solution in the form of copper sulfate. We see that the copper has brightened. There is very little left until it completely disappears. The layer is very thin and it will disappear now.

After about five minutes, the board is cleaned, there are small spots left that need to be cleaned with a brush to speed up the process. Using a soft brush, remove any remaining copper.

The metal tip is wrapped with electrical tape to prevent it from being etched. We take white spirit, which dissolves printer toner well. We need to clean the board to prepare it for tinning. You can also clean with acetone or use nail polish remover. After washing off the toner, the resulting product shines with copper traces.

Tinning

We will tin with Rose alloy. To do this, we need a ladle, which will be damaged and no longer suitable for anything. A little citric acid, gloves, tweezers and the alloy itself. Rose has a melting point of just under 100 degrees. It consists of small granules, one of which is enough to tinning a board. Add a spoonful of citric acid and a few tablespoons of salt. And we boil it. We throw a grain of alloy onto the board.

Rose, if the temperature is sufficient, will melt. We try to smear it with a cotton swab. If it doesn’t melt, then you need to add more salt to raise the boiling point. The alloy should spread easily and effortlessly into a thin layer. We spread the alloy without lumps so that SMD elements can easily become. Now, within the framework of LUT technology, you can proceed to the next stage.

Drilling the board

Let's start drilling. A high-speed mini drill with a collet clamp was used. It allows you to clamp drills without distortion. Drills with a thicker shank are better. Drills of two sizes 0.5 and 0.8 are used; they can be taken for one size of collet clamp. It is better if you use a machine, but you can also carefully drill with a drill, it must be held strictly vertically. Then the holes on the top and bottom sides will fit exactly into the track seats. After drilling, you can make sure that both sides match perfectly.

Cutting the board

Now you can use regular metal scissors to cut the board to size. This can only be done if it is thin enough. The board is ready for soldering. To solder SMD elements, you need a special paste SOLDER PASTE, W001 is used, which is usually sold in tubes. Don't forget to store it in the refrigerator. We carry out soldering with a soldering hair dryer. Apply a drop of solder paste to each soldering point. Just a little bit is needed. If you don't have a needle, you can do this with a regular toothpick. A small drop is enough for soldering; if there are too many, you can end up shorting adjacent tracks.

Parts distribution

We put the details in place. You can arrange them roughly, but make sure they stay on the paste. When soldering, they are aligned using surface tension forces. Particular attention should be paid to microcircuits - they need to be placed more precisely. They, of course, also level out. But if they are placed crookedly, then you can get a short circuit in the tracks and either resolder them or remove the resulting “snot” with a soldering iron.

For our paste, a temperature of 230 degrees is enough; we set the minimum airflow so as not to blow our parts off the board. Heat each part until the solder melts. We see that the parts are aligned in place. Soldering with a hairdryer is a pleasure. It takes a long time to prepare, but the soldering itself is quick and high quality. In this case, you can solder the entire side of the board at a time. As a result, it turns out much faster than with a soldering iron.

Now the hardest part, three output parts that also need to be soldered, the rest are already in place. Before soldering the LEDs, it is a good idea to check their polarity. We switch the tester to the diode testing mode and, by the glow of the LED, determine where the plus and minus are. Let's take a tuning resistor, install it in place and solder it using a soldering iron. Since the board is double-sided, it is necessary to solder on both sides. The pins of the parts were also used to transmit a signal between the parties.

For convenience, it is better to use a “third hand” card holder, but you can do it without it, although it is less convenient. The result is this board for charging the battery, made using LUT technology. It is double-sided, there are both SMD and lead parts. Just look how convenient this thing is.
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Quite many years ago I first learned about making circuit boards using Laser Ironing Technology. For me it was akin to the invention of the wheel.
Read the continuation of the story under the cut.

Before this, boards were painted with varnish using a drawing pen. To print boards using LUT technology, I even bought a laser printer (about 12 years ago it was very expensive). In the process of working, I tried a bunch of different types of paper. And more than one square meter of boards made using this technology was made; on the third I stopped counting. Currently, I have settled on paper from Popular Mechanics magazine; before that I used paper from Kitchens and Bathrooms magazine, but it has disappeared from sale.
But just recently, while reading reviews on Muska, I accidentally saw paper for printing boards in one of the reviews, went to Ali and immediately ordered myself a trial 10 pieces of leaves, deciding that if I like it, I’ll order 50, since the price difference is between 10 and 50 only about twice.
By the way, be careful, I posted a link to the lot, but now in this place there is a lot of 50 pieces for 10 something bucks, while the name of the link remains the same, 10 sheets.

I recently received my order. What I feared most happened, the paper arrived crumpled.
As everyone understands, putting crumpled paper into a printer is dangerous; the cost of repairs can be greater than the cost of the paper itself. I opened a dispute for a 50% refund, since after cutting I can use about that much.

The paper was simply in a large envelope, without a package or file, and a piece of some kind of cardboard was inserted, and this piece of cardboard was smaller in size than the paper. Actually, the main damage was in places where the cardboard was missing.

In the photo, the magazine I used before and the paper I received, I chose a leaf more carefully.

To prevent the printer from chewing on my new leaf, I had to cut off part of it, but I didn’t cut off the other side, since it’s not critical there, the main thing is just not to print anything in that area.

Well, since such paper is a very specific product, there is simply no way without testing.

In general, everyone who is interested, welcome to the spoiler.

Printed circuit board, how it's done.

First I trace the printed circuit board, I use the Sprint Layout 6 program, before that I used version 3 for a very long time, and I still can’t get used to the differences in control.

When making a board, I always leave a 5mm wide protective zone around the perimeter, so the workpiece is taken 10mm longer and wider than the required board, which is convenient for me.

The workpiece is cleaned with fine sandpaper; it is not the mirror surface that is important, but rather a lot of micro-scratches, then the toner will hold better.

We print our future board on paper (I usually print 2 pieces at once, just in case), on the smooth side, by the way, the whole process was done in one take, i.e. I didn’t adjust or redo anything specifically for the review, that was the point of the test.
Don’t forget that you need to print in a mirror image with respect to the required printed circuit board design.

Next, I place the blank on a specially prepared book :), or rather, it is not a book, but an annual binder of Radio magazines, bound in cardboard. I do this so that the workpiece does not slide during the process and does not spoil what is under it due to heat.

After this, I lay the printout with a drawing on the copper, then cover it with a sheet of ordinary printer paper on top, this way it slips less at the initial stage, the most difficult moment is to prevent the sheet with the print from sliding to the side, I first place the iron with the wide part on the book and paper, and then smoothly I lower it onto the workpiece.

Then, using smooth movements, with a little pressure, we iron our future board, I make several passes from different sides of the board so that the edges are ironed better, you can’t press too hard, otherwise the toner may float, if you don’t press at all, then most likely the toner will not stick to the workpiece. I iron this blank for about a minute.
By the way, I use Static Control toner, in my opinion this is the best toner for LUT...

The gluing process is complete, the paper adheres smoothly and beautifully.

Now we throw our board into a bowl of water for 5-10 minutes, you can leave the water on, this will help the paper become softer faster.

After 5-10 minutes, under a slight pressure of water (preferably room temperature), roll up the paper with your finger, the tracks should remain in place, this is not required to be done too carefully, since if the toner is erased with your finger, then such a board must be redone; normally glued toner cannot be erased with your finger , it just gets scratched.

The photo shows the result of transferring the drawing onto fiberglass. The toner is black in color; before, when I used magazine paper, the toner had a grayish tint because there were paper particles left on it. Everything is beautiful here, the holes are clean, there are no sticks between the tracks.
I specifically selected a printed circuit board for the test with both large filled polygons and small traces.

Before etching, I make this “table”: in the corners of the board, in places free from the drawing, I drill 4 holes into which I insert matches (or toothpicks), while the board is positioned with the drawing facing down.

Boards are usually etched with a solution of ferric chloride in water.
(III)
After immersing the board in the solution, it must be lifted almost immediately and air bubbles removed, otherwise there will be unetched areas.

After some time (depending on the solution), the board is etched.

I wash off the toner that has already served its function with acetone (or any suitable solvent).

Well, here I will show you what kind of print quality I finally got.
The place for the processor is closer to the center of the board, the width of the contact pads is 0.45mm, the width of the tracks is 0.45-0.5mm. It can be seen that the shape of the pad is even perfectly preserved.

And this is a path along the edge of the board, there are two such places. I usually correct such places with a permanent waterproof marker; I didn’t do this on purpose for the test.

After washing off the toner, I drill the necessary holes, then I clean the board with sandpaper.

After all these operations, I just cut off the excess; if this is done before stripping, you can damage the tracks closest to the edge of the board with sandpaper. I go over the edges of the board a little with a file to remove sharp fiberglass residues from the scissors.

Now I coat the board with flux (I use alcohol F3) and tin the tracks.
I know some people don't do this, but I prefer the board with tinned traces. In general, it’s a matter of taste, well, copper does not oxidize, and microcracks are filled with solder.

The last step is to wash off the remaining flux with acetone.

That's it, the board is ready.

Yes, I know about the photo method, I know about applying a mask and silk-screen printing, etc. etc.
These are all good and very useful things, but I think that for most applications the option I described is sufficient. Making a board this way is very quick and easy, and you need to have a minimum of chemicals and tools.
The board I made may be featured in one of my future reviews; some readers will probably even find out what kind of device it will be.

In general, my resume.
Pros.
I liked it, I think I'll order 50 or 100 sheets.
The toner sticks well from the base.

Minuses.
The seller packed it very poorly, for which he received a big minus.
The price, especially the price when buying a lot of 10 sheets, is quite enough for a sample, although looking for magazines and then sheets in magazines without pictures (for printing it is better to use either white pages or only with text) is getting pretty boring.

In general, experts, don’t judge strictly, I tried to describe it as best I could, I will be very glad for advice and additions, and I hope that my review helped someone.
And yes, I know that it’s cheaper on BiK :)))

I'm planning to buy +185 Add to favorites I liked the review +132 +305

FLUT - a modified version of LUT

So we have decided what we will assemble and before we start soldering we need what we will actually solder on - a printed circuit board.

By far the most popular method of producing printed circuit boards at home is LUT - the so-called Laser-Ironing Technology.

The essence of the technology is simple - we print an image of the tracks onto a certain medium using a laser printer, taking advantage of the remarkable property of toner (this is the powder with which laser printer cartridges are refilled) to melt and stick to flat surfaces, heat the resulting image using an iron and transfer the image to a prepared piece of fiberglass. Then we throw the textolite with the image into the ferric chloride solution and wait for the copper not covered with toner to be etched (dissolved). As a result, we get a printed circuit board with copper tracks. In general, the classic LUT is described in all its diversity on many amateur radio forums and websites.

So-called "modified" LUT in fact, it is not much different from the usual one, the key point here is the method of transferring the image onto the textolite. With the classic method, the image is printed on paper or a special film for printing on a laser printer; in a modified version we will use regular food foil. I used both methods - and for me the advantages of the modified LUT are obvious - it is much simpler, more efficient and faster. In any case, the manufacturing principles remain the same, so as the story progresses, everything will become clear.

So what do we need

sheets of ordinary office paper, food foil (regular, not very thick)
regular scissors, a little glue (PVA or something similar)
iron (an old used one is probably better, but I use a regular one that is used in everyday life :) - if you do everything carefully, nothing bad will happen to it)
laser printer (also preferably a dead one, simpler, since there is still a small risk of ruining the cartridge by scratching the photo roller)
naturally a computer and a file with an image of a printed circuit board on a scale of 1:1
fiberglass (in our case, one-sided, that is, covered with a layer of copper on one side) - a piece of a suitable size
metal scissors or a hacksaw - in general, anything suitable for cutting fiberglass
a small plastic(!) tray for etching (packages of cakes and other sweets are very suitable for this purpose)
ferric chloride (available at any store that sells radio accessories)
a thick book (you'll understand why along the way)
sandpaper (“null” or any fine-grained)

We are preparing an image for transfer to textolite. Take a sheet of paper and a roll of food foil. The foil should be thin enough, even (not wrinkled), ideally buy yourself a new roll for experiments and not drag scraps from the kitchen.

Cut a piece of foil the same width as the paper you are using.

We take glue (I use PVA) and coat the foil around the perimeter, not very thickly, but enough so that the foil sticks around the perimeter when you stick the foil on a sheet of paper. We glue. We get a sheet of paper with foil glued on top. The foil should be glued only around the perimeter, at the edges!

Next, take the file with the image of the signet and tear it off in a suitable editor. If it is a pdf, then open it in Adobe Reader (Adobe Acrobat), Adobe Illustrator or Photoshop - in general, whichever you like best.
Let me make a small remark - it is very useful for a DIYer to freely handle a computer and graphics packages - both when preparing signets and when working on cases for his creations, especially since all this is very simple.
If the signet is laid out in a special program (such as P-Cad or SprintLayout), then open it in this program accordingly.
A small note regarding stamps in pdf - when printing, we always uncheck the fit to page or similar checkbox - that is, we print with the original dimensions, no scaling. We pay attention to how the image is prepared - sometimes when printing it is necessary to obtain mirror image.
In normally prepared projects, you can navigate by the inscriptions on the board (they should be printed in mirror image). Fortunately, in most cases, no manipulations with the image are required during printing - the drawing is ready for translation, the inscriptions on the drawing are mirrored (bourgeois sometimes additionally write “ready for transfer”).
We take our prepared sheet, covered with foil, and print the image of the board on it. We try to ensure that the image is printed in such a way that it does not go over the edges - where the foil is glued to the paper.

Theoretically, if we glued the foil poorly and our sandwich of foil and paper jammed the printer, there is a chance that you will scratch the photo roll of the cartridge. But, to be honest, the probability is not great. However, I warned you.

Now we prepare fiberglass

We cut off the piece of PCB we need. I use good metal scissors; you can cut with a hacksaw or whatever is more convenient for you. We sand what we cut off with sandpaper. Don't overdo it - the copper layer is quite thin, we need to sand the top layer a little. As a rule, the layer begins to shine after a little processing.

After we have sanded the PCB it needs to be degreased. We simply degrease it - wash the board in the bathroom with soap. Rinse well. We carefully take the textolite by the edges so as not to stain the copper surface with our fingers, wipe it with a soft cloth (an old towel is best for this). :) Now we have almost everything ready to transfer the image.

Now we need to trim the prepared image - we cut it along the edges, leaving stripes on one or both sides so that we can wrap the PCB and secure the foil.

Since our foil was glued to the paper only at the edges, after we cropped the image, we received a piece of foil with an image printed on it. All these manipulations could not be done, but you are unlikely to be able to print directly on foil.
Coat the edge with glue.

We place the edge under the textolite blank.

We bend the foil and place the image on the copper surface. Slightly iron the fold.

After this, we take a sheet of plain paper, bend it in half, and put into it our piece of PCB wrapped in foil with an image.

Warming up the iron

After the iron has warmed up well (set the temperature to maximum), we carefully begin to iron the PCB sandwich with foil through the paper. Then we press the iron to the workpiece and heat it for 20-30 seconds. It is important not to overheat the workpiece (otherwise the toner will “float” - the tracks will turn out fuzzy and blurred. As a result of severe overheating, the toner will not stick to the copper coating, will become brittle, and will crumble. At the same time, it is important not to underheat the toner.
After we have heated the workpiece, it must be placed under a press. To do this, take the book we have prepared (preferably thicker and heavier) and quickly, before the workpiece has cooled down, put it in the book, close it and stand on the book. :) We wait about three minutes. We take it out.

Carefully unfold the sheet of paper and remove the textolite with the adhered foil. If you look closely, tracks are visible through the foil. Already at this stage you can see how well the image has stuck to the copper.

Now we are ready for etching

In principle, there are a lot of etching methods (from etching in weak solutions such as Mole to extreme ones - etching in hydrochloric acid), but it is better to use a generally accepted means - ferric chloride. Let's take ferric chloride. Dissolve in a small amount of warm or hot water. We place our workpiece in the bath (be careful with hot water - thin plastic cannot withstand the temperature of boiling water!).

Fill in the ferric chloride solution. First, the aluminum foil is etched off.

A stormy process begins. During the reaction with ferric chloride, aluminum releases a lot of heat, the process proceeds violently and quickly with the release of vapors (most likely unsafe for health - be careful).

The aluminum is quickly etched away revealing the imprinted pattern. The etched foil settles in brown flakes. It is precisely for the reason that after etching the foil, the ferric chloride solution loses its effectiveness, I keep a separate container with old “bleach” specifically to use it for etching the foil.

As you can see, the drawing was printed well.

Gently shake the bath and wash off the flakes. Let's examine the drawing. At this stage, if something goes wrong (some tracks are not printed), you can dry the board and complete the design with a marker or paint.

Things didn’t work out so smoothly for me - I overheated the workpiece and some of the tracks “floated”.

After we have examined how well our drawing has been printed, we can continue etching. Place the workpiece in a ferric chloride solution. The board is etched faster if the solution is heated and mixed. Regarding heating - some heat with fluorescent lamps, others initially try to dissolve bleach with hot water - in general, the field for experimentation here is quite wide. You can also mix the solution in different ways - small boards can be placed in a glass jar, filled with bleach and shaken methodically, some poison the boards by pouring the solution into a thick plastic bag (of course not full of holes) - in this case, be careful with sharp corners - fiberglass is an easy bag may tear. I etch in a plastic bath (see photo) - stirring the solution and shaking the bath so that the solution washes the board. There are special devices for etching printed circuit boards - if you have extra money and a desire to etch for a long time and in large quantities, I think purchasing such a thing will be a valuable acquisition.

Here's an almost etched view of the board:

Flaw detection

So the board is almost completely etched. We take out the board and wash off the remaining bleach solution from it.

However, the drawing did not print as well as we thought at first - in some places there are places where the copper was not etched. In this case, you can leave the board to etch further, but I decided to leave this defect as an example - a little later we will solve this problem - we will cut off the excess with a scalpel. It’s true that we often have to work with a scalpel in cases where the signet is spread very tightly - the tracks and mounting spots are located very close and when transferring the image, if we overheat the toner, the tracks can “spread” and merge with neighboring elements.

And here is an example of another typical situation - a break in the track. We will treat it using a soldering iron, solder and pieces of radio element leads or pieces of thin wire.

Let's put off eliminating the shortcomings until later and clear the toner tracks. Take a small piece of cloth, soak it in acetone and wipe the paths.

After we have washed off the acetone, we wash the board again to wash away the remaining acetone and ferric chloride solution. I usually wash the board well with soap and "lots of water".

After we have washed the board, we wipe it dry (moisture naturally causes corrosion and is harmful to our board). Usually I go over the paths a little more with a zero brush, bringing the paths to a shine.
Now you can carefully inspect the board for flaws - there should be no breaks in tracks or connections on the board where they are not provided. It is convenient to look at the paths at a slightly angle so that they shine a little - so their surface and all the imperfections are clearly visible. There were two obvious flaws on our board - one was unetched areas - we cut them off with a scalpel. The other is a break in the track - we solder it with solder - you just need to take more solder than usual on the soldering iron tip (so that a small drop forms) and solder the break point so that a solder is formed.

Half and drilling

After etching, many people additionally tin the entire board completely, I usually don’t do this - just carefully inspect the board for defects, checking the board pattern that we printed. You should approach this as responsibly as possible - an undetected board defect will lead to the fact that the project will not work or will work but not as it should. I think this is obvious.
All we have to do is drill holes on the board and start soldering.

Since I simultaneously etched several boards and at the same time tried to capture this process, I did not end up with a very high-quality board. True, this turned out to be a good time to demonstrate possible problems that you may encounter during the manufacture of printed circuit boards. I'm sure you will do much better.

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© 2008 Igor Kotov. The article has been cut up and shoveled. Errors corrected. Layout and optimization of photos for the web.
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LUT on the contrary

How to make a printed circuit board at home. Or LUT (laser ironing technology) - vice versa.

By “LUT” we mean thermal transfer of toner from paper to the metallization surface of the future printed circuit board.

The most interesting videos on Youtube

Preface

I tried many times to make a printed circuit board using LUT, but I never managed to get a reliable, easily repeatable result. In addition, when making a board, I need etched holes in the pads no larger than 0.5 mm in size. Subsequently, I use them when drilling, in order to center a drill with a diameter of 0.75 mm.

Defects manifest themselves in the form of a shift or change in the width of the tracks, as well as in the unequal thickness of the toner remaining on the copper foil after removing the paper. In addition, when removing the paper before etching, it is problematic to clean every hole in the toner of any cellulose residue. As a result, when etching a printed circuit board, additional difficulties arise, which were avoided only by doing the opposite.

I assume that the reason causing the marriage is the following.

Paper, when heated to a high temperature, begins to warp. While the temperature of foil fiberglass is always slightly lower. The toner partially adheres to the foil, but remains melted on the paper side. When warped, the paper moves and changes the original shape of the conductors.

LUT is the opposite.

At the very beginning, I want to warn you that the technology is not without certain disadvantages.

The first is the lack of special paper for thermal transfer, instead of which I suggest choosing suitable paper for self-adhesive labels. Unfortunately, not all paper is suitable. You need to choose one whose labels are denser and the backing has a good, smooth surface.

The second disadvantage is that the size of the printed circuit board is limited by the size of the soleplate of the iron. In addition, not every iron can heat foil fiberglass laminate evenly enough, so it is better to choose the most massive one.

However, despite all these shortcomings, the technology described below allowed me to obtain a stable, easily repeatable result in small-scale production.

The essence of the change in the traditional process is that it is proposed to heat not the paper with toner, but the foil fiberglass itself.

The main advantage is that with this method it is easy to control the temperature in the toner melting zone. In addition, the rubber roller allows you to evenly distribute the pressure and prevent crushing of the toner. (I write everywhere about foil fiberglass, since I have not tested other materials).

The technology is equally well suited for foil fiberglass laminate of different thicknesses, but it is better to use material no thicker than one millimeter, as it is easy to cut with scissors.

So, we take a piece of the most shabby foil fiberglass laminate and process it with sandpaper. You should not use very large sandpaper, as it can damage future tracks. However, you don’t have to sand it if you have a piece of new fiberglass. The copper surface must be thoroughly cleaned and degreased in any case.

Making a stencil for thermal transfer. To do this, we cut off the required piece from a sheet of paper for labels and separate the labels themselves from the backing. You should leave a piece of label at the beginning of the sheet to prevent the backing from getting stuck in the printer mechanism.

Do not touch with your hands the areas on the substrate where toner will subsequently be applied.

If the thickness of the foil fiberglass laminate is one millimeter or less, then the distance between the edges of the individual boards can be chosen to be 0.2 mm; if it is larger and you are going to cut the workpiece with a hacksaw, then 1.5-2.0 mm, depending on the thickness of the blade and the processing tolerance.

I use the toner layer that is installed by default in the printer driver, but “B & W Halftones:” (B/W Halftone) should be selected “Solid”. In other words, you need to prevent the appearance of a raster. You may not see it on the stencil, but it may affect the thickness of the toner.

We fix the stencil on a piece of foil fiberglass with paper clips. We attach another paper clip to the free edge of the stencil so that it does not come into contact with the iron.

The melting point of different brands of toner is approximately 160-180C. Therefore, the temperature of the iron should be slightly higher by 10-20C. If your iron does not heat up to a temperature of 180C, then you will have to adjust it.

Before heating, the soleplate of the iron should be thoroughly cleaned of grease and other contaminants!

We heat the iron to a temperature of 180-190 degrees and press it tightly against the foil fiberglass as shown in the figure. If you position the iron differently, the board may heat up too unevenly, since usually the iron heats up 20-30C more in the wide part. Wait two minutes.

After this, remove the iron and in one motion, forcefully roll the stencil onto the foil fiberglass using a rubber roller for rolling photographs.

If during rolling the toner is crushed, that is, the tracks move to the side or change their shape, then you should reduce the amount of toner in the printer driver.

It is necessary that the center of the roller always moves along the center of the board. The roller handle must be held in such a way as to prevent the appearance of a force vector directed “around” the handle.

We roll the stencil tightly a few more times and press the resulting “sandwich” with something heavy, after laying down a newspaper folded several times in order to evenly distribute the weight.

The stencil should be rolled in the same direction every time. The roller begins to move from the place where the stencil is attached.

After about ten minutes you can remove the press and remove the stencil. This is what happened.

The excess part of the workpiece can be cut off and used next time.

Now you need to glue something to the back side of the board in any way so that you can later hold this board during etching. (I use hot glue.)

We etch the board in a ferric chloride solution.

How to prepare the solution?

If a jar of ferric chloride is unsealed, then most likely there is already a super-concentrated solution there. It can be poured into a pickling bowl and a little water added.

If ferric chloride has not yet been covered with water, you can do it yourself. You can probably get the crystals themselves out of the jar, but don’t use heirloom silver for this.

Keep in mind that the etching process will not work in a highly concentrated solution, so once you have such a solution, you need to add a little water.

It is best to use a vinyl plastic photo bath as a dish, but you can use any other one.

The picture shows that the board floats on the surface of the solution due to its surface tension. This method is good because the etching products do not linger on the surface of the board, but immediately sink to the bottom of the bath.

At the very beginning of etching, you need to make sure that there are no air bubbles left under the board. During the etching process, it is advisable to check that the etching proceeds evenly over the entire surface of the board.

If there is any heterogeneity, then you need to activate the process with an old toothbrush or something similar. But this must be done carefully so as not to destroy the toner layer.

Particular attention should be paid to the holes in the contact pads. The areas where the etching process did not start immediately are lighter. In principle, it is enough to darken the entire surface and all holes at the very beginning of the process, and then success is a foregone conclusion.

In those places where the copper has been completely etched, the fiberglass begins to show through.

If the main part of the board was etched in 15 minutes, then you should not increase the total etching time more than twice, that is, more than 30 minutes. Further etching will not only reduce the width of the conductors, but may also partially destroy the toner.

Typically, all 0.5mm holes in the contact pads are etched in twice the time.

The motor turns a small eccentric, which creates vibrations in the solution (not necessary if you periodically lift and move the board).

Wash off the toner with a swab soaked in acetone.

This is what happened. On the left, the board is still covered with toner. The width of the tracks is 0.4mm.

We drill holes, not forgetting to periodically sharpen the drill.

Now you can remove the burrs formed on the copper during drilling. To do this, we first roll them up using a ball bearing secured in some convenient mandrel. In this case, it is better to place the board on a hard, flat surface. Then, using fine sandpaper, remove oxide from the surface of the copper, if it has formed.

We tin the workpiece, for which we first coat it with a layer of flux.

We cut the workpiece into separate boards.

At the request of the workers, I went to the stationery store and photographed the packaging with Self-adhesive labels. This paper is not suitable for thermal transfer. Although, if there is no other one, then you can use this one after some modification. More details in the next article about LUT.

On the left is the front side of the package, and on the right, respectively, is the back. On the back side there are options for placing self-adhesive labels on an A4 sheet. Large numbers are the number of labels of the same size placed on one A4 sheet.

All the above words about packaging are not directly related to the paper I selected. As it turns out, sellers use this packaging to store completely different types of paper.

Suspicions crept in when I bought different papers in different stores, which were taken out of the same package. The sellers said something about a manufacturer who changes the quality of paper like gloves. But today I talked with the owner of a small wholesale store and he told me that it turns out that sellers simply use the packaging as a container for paper, which initially does not have packaging. Or rather, there is packaging, but it’s just a thin transparent film.

So, the paper that turned out to be the most convenient for thermal transfer turned out to be produced by the Finnish company "Campas". And since there are no identifying marks on the small packaging, it is unlikely to be identified without testing.

The need to make hardware periodically arises among many techies. Sometimes the task allows you to screw everything up with wires on the breadboard, and sometimes, unfortunately, you need something more serious. So one day I was overtaken by the need to make printed circuit boards... Laser-ironing technology for handicraft manufacturing of circuit boards is at first very repulsive due to its randomness (what to print on, how to heat it, with what force to press, how to tear it off, etc.), but friends shared their experience , and it turned out that it really isn't that difficult. LUT is undeniably cheaper than any other option, and (surprisingly) quite suitable for two-layer boards.

Those who are interested in something more complex, more expensive and more precise can do it, but our technique (the main element of which is special paper) allows us to consistently work on 0.3/0.3 mm busbars, so in our community there is an opinion that photoresists are not needed.

Anyone who doesn’t see the point in handicraft production of boards will most likely be able to remember a couple of cases when they had to cut tracks and solder wiring on a whole batch of boards. And having made one board at home, you can thoroughly debug it and gain confidence in factory boards.

Below the cut, I will share a deterministic method for manufacturing two-layer printed circuit boards using LUT technology with various backup circuits in case of jambs. From idea to inclusion. We will work with KiCad, Inkscape, sandpaper, iron, ammonium persulfate and engraver.

Any device starts with a circuit. Most board errors can be eliminated at the design stage. And in order for the circuit to be guaranteed to match the board, you need good EDA software. For example, KiCad.

KiCad --> Board

If you are still working with proprietary limited solutions, start with the article or skip this section.

We use the recently released KiCad 5, because I deeply like this program, its community (including CERN) and the idea of multi-platform FOSS in general.

So the algorithm with life hacks:

Board --> SVG

When the board is ready, you need to convert it to SVG for further refinement. It’s better to unload the board from EDA without mirroring, so as not to get confused and mirror it properly.

And we need to mirror it only front layer F.Cu. Since we look at the back layer of B.Cu in the editor from the front, it is already mirrored. For reliability, it is better to place at least some text on both layers and make sure that this text is not readable))

( , ) It is better to upload from KiCad via File | Plot, since it is possible to make all the holes 0.35 mm at once. For manual LUT, greasy holes are not needed, it is better to have more copper and clean it off with a drill.

Actually:

Load both layers into Inkscape.
We set the document measurement units to millimeters, and the A4 sheet format.
Adding even more white lettering to the metallization areas. KiCad can't do this, write in the comments if your EDA can.
Let's group so that there are only two objects.
Align (Ctrl+Shift+A), the distance between the layers (their overall holes) should be at least a centimeter.
We mirror the front layer using the button on the top toolbar.
Save as SVG.

Now we need to send the SVG to the printer on plain paper. And do the following with this paper:

Attach components to it and check the footprints (which, in any case, have already come from the store: if you have more than three to five components on the board, it’s difficult to trace everything in one evening)
Attach to the PCB and punch 4 dimensional holes in the corners that we added
- Take a core (or nail) with a hammer and make a super-precise, shallow dent that will absorb stray drill bits. The impact force must be such as not to deform the board.
Drill 4 holes with the thinnest drill (0.6-0.8) exactly at 90 degrees. This is perhaps the most difficult part, but mistakes are acceptable; a method for their subsequent correction has been invented.
- If you have a machine, you are lucky.
- If you have a CNC, you are very lucky; figure out all the holes according to the DRL file right now without any cores.

It is easy to guess that the holes are needed to accurately orient the front layer relative to the back one. If you want something simpler, there is a way without holes: very precisely fold the piece of paper with the template and place the PCB inside. As already mentioned, a slight deviation will not be fatal (unless, of course, the holes have not yet been drilled)

Another folding modification:
We place freshly printed sheets with the top and bottom layers on top of each other, shining them through with a lamp and aligning them. We fasten in several places along the edges. We put textolite into the resulting envelope.

shared . Thank you!

Ok, this is the section about SVG, and we’ve already moved on to the machines... That’s it, the final touch on SVG and you won’t need a computer anymore:

Fill everything with black so that parts of the PCB that do not belong to the board are not etched and do not saturate the ammonium persulfate with copper. Yes, ferric chloride is also possible, but ammonium is blue.

SVG --> Textolite

Also, we have information about the suitability of paper Black Diamond. Other brands may or may not have the required properties. HP does not fit exactly (melts under the iron), Lomond fits conditionally, "but somehow average". You can experiment with different glossy photo paper for inkjet printing. Write in the comments what it’s like with other papers)

Algorithm:

Set the iron to heat up to maximum temperature.
We grind the textolite on both sides with fine sandpaper and a plumbing abrasive sponge (,), dish sponge or an abrasive eraser.
If your printer can accept formats other than A4, Cut a strip from A4 to the size of the image. Paper is extremely valuable: if you managed to get it, you need to save it.
We push it into the printer with the narrow side. We check that the image of the two layers of the board does not exceed the width of the cut strip in width and 210 in height.
We laser print with original toner in a cartridge on this glossy photo paper for inkjet printers.
Without touching the toner, cut the layers into two separate pieces of paper and make large holes on both layers.
We insert straight pins (for example, from a PLS/PLD comb) into the 4 dimensional holes.
Place the front layer.
We iron it evenly, without pressing too hard, until the paper turns yellow (or any other signs from above, this is still LUT: it’s probably impossible to completely get rid of the magic). The pins can be pulled out when the paper begins to stick and loses its ability to move.
Without tearing the paper off the PCB, we repeat the last three steps with the back layer.
Let the textolite cool down: you can put the kettle on to warm up and begin to dissolve the ammonium persulfate.
Carefully peel off the excess paper from the cooled PCB (without water, this is extremely important). The toner should come off along with the glossy layer of photo paper, that’s how it was intended.

In case of mistakes, you can erase one of the layers with acetone, place the already torn piece of paper on the opposite layer (so that the toner does not come off the board and transfer to the board on which you are ironing) and repeat.

Textolite --> Textolite with tracks

For etching, we need a plastic container (or any non-metallic container in which the board will fit lying down). And also, a disposable spoon or varibashi for stirring the board (against bubbles that interfere with etching).

It is recommended to dilute ammonium persulfate in warm water 1:2. But this is a fairly high concentration, 1:3 or even 1:4 is enough. After all, you can stir it some more later. The recommended temperature for unwinding is 40-50 degrees.

However, keep in mind that overheating all kinds of chemicals is quite dangerous. High concentration, high temperature and copper salts can lead to creepy results.