Choosing paper for loot. Paper for making printed circuit boards using LUT technology or how to make a printed circuit board at home
In mine, I mentioned the production of printed circuit boards using special Chinese paper for LUT. I was bombarded with questions. And just recently I recommended it to a friend, to whom it was difficult for me to explain exactly how to use such paper. So I decided to make a short video review about using Chinese paper.
I bought the paper on Aliexpress. There is nothing complicated, try it! Now on Aliexpress you can choose the Russian language and prices in rubles - China is turning its face to the Russian consumer. You can pay by bank card, Yandex.Money, WebMoney, QIWI, etc. The paper is sent by regular mail with tracking.
Expand the menu at the top right on the Aliexpress website: there is now a separate Russian version of the site.
Order 10
A4 sheets. Free shipping.
Order a pack of thermal transfer paper, 50
A4 sheets. Free shipping.
Order a pack of thermal transfer paper, 100
A4 sheets. Free shipping.
Early on, I tried different papers for LUT, most often making do with scrap paper from glossy magazines. I rarely liked the result. There were also difficulties with soaking; the toner did not always remain completely on the board. During etching, cavities could form in the toner itself due to air bubbles and other inconveniences. One way or another, the quality and repeatability did not suit me.
Miraculously I came across the subject. All of the listed disadvantages are absent when using this miracle piece of paper! I'm happy as an elephant. The result is comparable in quality to the photo process, but without fussing with darkness, UV lamps, etc.
Printed track pattern
I was doing a lot of PP at once, so I printed out a whole A4 sheet on a laser printer.
How to use:
1. Print the drawing on the shiny side sheet on a laser printer.
2. Place the sheet on a prepared piece of PCB (polished, degreased) and run it through a laminator or iron it at a temperature of 150-180C. This is where thermal transfer of the drawing occurs. Ironing takes 30-90 seconds, depending on the size of the workpiece. There is no need to be zealous with pressure, the main thing is uniform heating across the plane.
3. Remove the paper. You just need to wet it with lukewarm water. The paper soaks completely within a few seconds and without a trace!
4. We etch the board in the usual way, for example, in ferric chloride.
5. Wash off the toner with gasoline, acetone, etc. solvents.
The finished result
Photo by Igor Kotov (datagor), added 11/17/2014
Video of using Chinese thermal transfer paper
Better to see once than hear a hundred times. I offer beginners a short video overview of the process. And the luminaries can rate the speed!Ironing
Soaking
Links
Order a pack of thermal transfer paper, 10 A4 sheets. Free shipping.Order a pack of thermal transfer paper, 50 A4 sheets. Free shipping.
Order a pack of thermal transfer paper, 100 A4 sheets. Free shipping.
In this study, I tried to find the real limits of LUT application, find out what the minimum gaps and paths are and decide on the best paper for the process. The practical goal is to achieve the coveted 0.1mm, which, as some say, can be done with LUT.
Note: all photos are of very high resolution, from 300KB to 4MB in size, so that all the details are visible. Therefore, I did not insert them into the text, but provide links to them.
General process
I will not go into theory, but will simply describe what I do in my home environment.
Sprint Layout program, I print on an HP LaserJet 1200 (600dpi), foiled textolite 1.5mm thick, single-sided, small iron, travel iron, etching with ferric chloride, toner erased with solvent 646.
Before printing, I sand the board with 1000 sandpaper and wipe it with 646 solvent.
Paper selection
Paper selection criteria:
- availability
- good toner coverage and adhesion when printing
- good transfer of toner to board from paper
- ease of removal from the board after toner transfer
- coating (or blending) the toner with a layer that seals the pores in it.
The last point requires clarification. The bottom line is that all LUT technology is based on laser printing, and any laser printing is based on toner, and any toner suitable for LUT suffers from one very unpleasant drawback: porosity. Because of this, strong etching of the tracks occurs, even with a short etching time. And most importantly, large surfaces that are covered with toner are etched. They seem to be corroded from above, sometimes right through. Photo paper, in particular, has a pseudo photo layer that can mix with toner at high temperatures, covering it with an impenetrable plastic-like film that is resistant to etching compounds. However, according to the experience of other amateurs, this layer often also lies tightly on the board and is difficult to peel off, or gets clogged into the gaps, which makes it either difficult or impossible to make small gaps. Abroad, there is a commercial solution to this problem - GreenTRF folk. If anyone is interested, read Google.
From the very beginning I tried regular 80gsm office paper. Complete nonsense. Doesn't release toner.
Then I did it on the pages of glossy magazines. It turns out well, but it takes a long time to soak, the transfer of toner to the board is not complete, the toner spreads a lot when heated with an iron.
Branded HP matte photo paper for inkjet printers. The toner transfers poorly to the board, no, the toner is not covered with anything on top, it remains porous.
HP Semi-Gloss Photo Paper. After 30 minutes of soaking, it is impossible to remove the paper from the board. The entire toner is covered in white plastic. You can only peel it off with toner.
Thermal transfer paper for inkjet printers for transferring to clothing. I was afraid to push it into the laser machine - it melts too easily. I wanted to melt the toner aors. Complete failure.
It would seem that everything was lost. There is no way out, try the same thing from other companies (still a lot of money down the drain) or change hands.
But here's what Thomas Edison said:
“Too many people break down without even realizing how close to success they were when they lost heart.”
And he was very right!
After all this torment, I went to read about GreenTRF, about commercial systems for LUTs, how they work, I tried to understand, and when I read about press"n"peel, I read that the temperature there does not need to be very high (as for polyester). And I thought, maybe I overheated too.
I placed the iron between points 1 and 2 and used the same photo paper from HP Premium, which stuck tightly. I warmed it up for 3 minutes, went to the bathroom, turned on the cold water and pulled the paper. She walked away without any resistance at all! About 90 percent of the design remains on copper! And very black. There is almost no toner on paper!
After 3 trials, I found that the optimal value is one division above 2 points (on my iron there are still a lot of divisions between the points). In this case, the back of the paper is already beginning to melt, so you need to put 1 sheet of plain paper underneath. I tested on a small scarf, so I didn’t need to move the iron back and forth, but I pressed normally and sometimes went along the contour with a little pressure. Warm up: 3.5-4 minutes.
After that, I immediately take the piece of paper, go to the bathroom, put it under cold water, and after 3 seconds I remove the paper in one motion. Here's what happens:
/elektro/tt/IMG_3517.jpg
Where there was toner, the paper turns bluish, and the toner on the board feels like plastic, shiny and glossy. However, there is no photo layer anywhere in the cracks! There's nothing to scratch! The paper, by the way, is very interesting; when the glossy side gets wet, it becomes covered with some kind of slippery paste, like real photographic paper. As you can see, the toner transferred perfectly! Beauty!
My LaserJet 1200 swallows both a full 10x15 sheet and a half 10x7 sheet.
Method of measurement
The method is simple: take a camera, a ruler and an object, place the ruler on top or next to the object and take close-up macro photography. We count the number of pixels in 1 mm on the ruler, count the number of pixels on the object, divide the latter by the first and get the size of the object in pixels.
For those. who doubts this measurement technology, I conducted an accuracy test. I have a chip from TI psp54310pwp in a very small package. According to the datasheet, his leg is 0.19 mm thick, and the distance between the middle of the legs is 0.65 mm. Using my method, after photographing the chip, the following values were obtained: 0.20 and 0.62, respectively. So, I think there will be no question of accuracy
/elektro/tt/4/IMG_3532.jpg
Testing for track and gap thickness
After that I made a steeper bath with ferric chloride. I etched everything out in 15 minutes. Here's the result:
/elektro/tt/IMG_3518.jpg
Looks great. All the tracks came out completely (even 0.05mm), the 0.1 gap didn’t come out at all (but no one hoped), but 0.2 was completely intact.
I test all the tracks with a multimeter - they are all intact. I'm testing the gaps. Oops, 0.2mm conducts! Here you can see the place where there is a bridge:
/elektro/tt/IMG_3521.jpg
(circled in red)
One movement of the needle over this area and the problem is eliminated.
But the question is, what are the real dimensions?
As before, apply a ruler and take a macro photo:
/elektro/tt/IMG_3521.jpg
And we get: per 1 mm: 30 pixels
Tracks:
- 0.05mm 5px 0.17mm
- 0.10mm 7px 0.23mm
- 0.15mm 9px 0.30mm
- 0.20mm 10px 0.33mm
Sadly. And the paper is super, and the hands are not hooks, it seems. But less than 0.17 does not work! I did the maximum filling with toner when printing (this is when the printer is instructed to print on transparent film), maybe if you don’t do it so thickly, the toner won’t spread as much when melted with an iron.
Gaps
- 0.2mm 6px 0.2mm
- 0.3mm 9px 0.3mm
- 0.4mm 13px 0.43mm
For some reason the gaps came out perfect!
Overall it turns out very nicely, but the paths, alas, are not the right size.
Speaking of the laser printer itself. My maximum is 600dpi. Those. 236 lines per 1 cm. I.e. 24 lines per 0.1mm. It seems to me that at such sizes the errors are already prohibitive for this printer. Especially with a recharged cartridge and a stale drum and unknown toner.
Who even knows how long the toner “floats” during printing? Let's do a simple experiment. We print the same layout on paper in normal mode and see how thick they are on the paper, even before transferring.
We carry out 4 experiments, the scale is a caliper (to be more precise):
- bold printing on photo paper
- regular printing on photo paper
- normal printing on plain A4 paper (after running through the printer several times)
- control measurement of the just made board.
We measure only track 0.1. The method is the same as described below (1mm in pixels is determined in each frame separately)
- bold printing on photo paper
/elektro/tt/3/IMG_3524.jpg
per 1 mm - 34 p.
track 0.1 - 6p. - 0.17 mm - regular printing on photo paper
/elektro/tt/3/IMG_3525.jpg
per 1 mm - 35 p.
track 0.1 - 5p. - 0.15 mm - normal printing on plain A4 paper
/elektro/tt/3/IMG_3526.jpg
per 1 mm - 35 p.
track 0.1 - 5p. - 0.15 mm - control measurement of a newly made board
/elektro/tt/3/IMG_3527.jpg
per 1 mm - 35 p.
track 0.1 - 7p. - 0.2 mm
In this light, I have a question: what kind of 0.1mm tracks can we talk about if the print itself is ALREADY thicker, and there will also be a melt during transfer? It is foolish to hope that they will be trimmed to the required width, because then the gaps will be trimmed and there will be problems there.
Could there be a problem with the printer? Maybe 600dpi is not enough? In the office, a test drawing was printed on a 1200 dpi printer (HP LJ 3055) on plain paper (80 g/m2) and on the same HP Premium Photo Paper, and at home the dimensions of the drawing were measured.
Measurement was done only on track 0.1 (simply taken as a reference, so as not to suffer too much).
Photo paper: 0.125 mm
Plain paper: 0.11 mm
Not bad, yes. Not like at home at 600dpi. However, the toner is clearly different and doesn’t stick to photo paper very well. Lots of hairiness. Tracks 0.05 are visually printed with gaps on photographic paper, but measurements showed that the size there is 0.09mm.
Converting to copper.
So, the size of the copper track is 0.1mm - 0.17mm
I etched it in a cool solution, everything came off in 10 minutes.
/elektro/tt/4/IMG_3538.jpg
(there are undercuts, with homemade 600dpi there is no such thing, in some places the toner just tears, it’s strange)
The resulting track size is 0.1mm - one is 0.18mm, the other is 0.20 (for some reason they came out different).
The track size is 0.05mm - 0.15mm, but it is terribly uneven, one track is torn in the middle.
One track of 0.05mm (well, which is actually 0.15) did not pass the electrical test, and the gap of 0.2 was also shorted. After running a paper knife across the gap, everything went away.
Conclusion: 1200 dpi does not help, and the toner there is less suitable.
So, a new test pattern:
/elektro/tt/4/IMG_3534.jpg
There are places where the toner simply did not adhere to the paper, I still don’t understand exactly why this sometimes happens, but it depends on how to run the water from the tap and when to pull the paper, it’s better to let the water go directly into the knock between the board and the paper.
It has added seats for SMD.
One has a contact width of 0.44 mm, a gap of 0.17 mm.
Second: contact width according to the pattern is 0.63mm, gap 0.62mm.
/elektro/tt/4/IMG_3544.jpg
At the top right there is still room for an SMD capacitor size 0402 (the frame is a silk screen type.
I take the mentioned HP photo paper, my printer with 600dpi. I'm typing.
Dimensions on paper:
- 0.63 mm - 0.63 mm
- 0.44 mm - 0.43 mm
- 0.1mm - 0.14 (already floated)
The resulting dimensions for the boards after etching:
- 0.63 mm - 0.65 mm
- 0.44 mm - 0.43 mm
- 0.1 mm - 0.22 mm
- 0.05 mm - 0.18 mm
And don’t ask me why 0.43 didn’t float. Maybe it’s some special size that the printer can print correctly and some kind of force when melting holds the toner together.
The nice thing is that the paths are smooth, without gnaws.
The electrical test showed that all the tracks are intact, and there is a short circuit in the 0.2 gap. One connection in one place. I removed it with a knife - no problem.
Out of 4 cases, in 100% there is a short circuit in the gap of 0.2 and in 100% this is treated with one pass of a knife or needle. It's probably better to do this by etching.
Checking the locations for the SMD showed that there are no short circuits at all. Since the size of the site is observed, the gaps are also observed. Those. there are gaps of about 0.17mm without short circuits. And don't ask why - I don't know!
conclusions
- HP Premium Photo Paper (Q199HF) rocks black!
- If you transfer toner using a laminator, then you MUST need a laminator with temperature control!
- You have to poison quickly! The longer you weed, the more weed.
- The temperature on the iron must be selected individually for the iron, toner, paper, and, possibly, the board (for this paper you need to find the minimum at which all the toner is transferred after 4-5 minutes of warming up).
- The limit of technology with a 600dpi printer and Chinese toner in a recharged cartridge is 0.18mm
- To get a track of 0.18-0.20, you need to draw 0.05-0.1 in the diagram! It is very important!
I think that the topic with 0.1mm tracks can be closed. There are no such tracks on LUT and there cannot be! But what is there is quite enough to make TQPF144 for AVR32 without any problems, one might even say that there are no problems at all (pad 0.25, gap 0.25 and everything is ok, there is a step of 0.5mm).
If someone thinks that they actually made a track with 0.1mm LUT, I’m waiting for a macro photo with an attached ruler, we’ll laugh together.
Some far-reaching conclusions
Glossy photo paper absorbs better than transparent film. The photo method uses a transparent film over a resist. The thickness of this film cannot be less than that of glossy photographic paper, i.e. we are talking about a minimum of 0.15mm. Further, when illuminated, shading or highlighting of the tracks can occur, which is why they can be thicker or thinner, and significantly in relation to 0.15 mm (i.e., for example, from 0.1 mm to 0.2 mm). In addition, experience with track 0.09 showed that it is easily etched and even chewed in places by the etching composition. This is all theory, since I have never used the photo method, but it seems to me that there is a limit of about 0.15mm. If someone thinks that they did less, take a macro photo with a ruler in the studio.
ATTENTION! ATTENTION! ATTENTION! ATTENTION!
Later it turned out that the specified HP Premium paper is absolutely not suitable for making boards larger than 3 by 5 cm, since when the paper is removed, scraps of toner come out. Read the next part for information on the correct paper. Second part .
ATTENTION! ATTENTION! ATTENTION! ATTENTION!
There is a method for making boards in which the tracks are printed using a laser printer on paper, and then the toner is transferred to PCB foil with further etching in ferric chloride or something else. This method is called LUT: it is very cheap, does not require special skills, and the finished boards are of excellent quality. So, for high-quality transfer of printer toner from one surface to another, special high-temperature transfer paper is used.
Ten sheets of A4 format are offered for a small price; they will arrive rolled into a tube. Smooth out the paper before use.
Instructions for use:
1) The pre-wired board must be printed on the smooth side of thermal paper.
2) Now you need to carefully place the special paper with the printed side facing the bonded copper and pass it through a laminator at a temperature of 150 - 180 degrees Celsius. You can also use an ordinary iron for this.
3) Remove the paper from the plastic foil PCB and place the board in a solution of ferric chloride to corrode the copper. To speed up the chemical reaction, heat the solution.
4) Finally, remove the PCB and then clean it with acetone or alcohol.
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 :)))
