When the board is etched, the photoresist comes off. Manufacturing of printed circuit boards using photoresist. Preparation and cleaning of PCB
Today I will tell you about the manufacture of a printed circuit board using film photoresist or the so-called photoresist technology for manufacturing printed circuit boards. Do not shout that LUT is cooler, cheaper and faster - I do not argue, but the photoresist has a higher resolution and is able to give results where LUT may not work. All of the following will apply to negative film resist. In my practice I use PF-VShch-50. The process of manufacturing a board using film photoresist can be divided into the following stages:1) preparation of the board blank and photomask;
2) applying a photoresist to the workpiece;
3) illumination of the workpiece with photoresist through the template;
4) development of the board drawing;
5) etching the board.
We cut the workpiece from foil-clad material with an allowance of at least 5 mm to the main size on each side. We print the template on film for the printer that is at hand. I have a laser and I print on universal double-sided film for laser printers and copiers. Whoever has an inkjet, then accordingly we take a film for inkjet. When printing, in the laser settings, we select the maximum print quality, turn off the toner saving - the more there is on the template, the better. As a result, we have the following:
The printer is old and the cartridge has been refilled a bunch of times, so the print quality is poor. Therefore, the toner on the template is transparent enough, but we need it to transmit as little light as possible, i.e. it is necessary to increase the optical density of the image. For these purposes, there is a tool for increasing the optical density of the negative Density Toner, but it was not possible to find it and it costs decently. I decided to use acetone - it turned out to be more than enough for my needs: we moisten a piece of medical cotton wool in acetone, throw it into a glass jar, put the template inside the jar with a pattern, twist the lid and set it to heat.
Heating can also be carried out on a radiator or some other thread (depending on your imagination). This process requires control so as not to overexpose the template in acetone vapor, otherwise the entire pattern will drain to the bottom of the can. In the photo, a template that has passed a pair of acetone - it has become somehow more black and shiny, try it - the result will be on your face.
We proceed to applying the photoresist to the workpiece foil, for this we stock up on approximately the following tools:
We roll out a roll of photoresist and cut out a piece with a knife on the workpiece with a small margin on the sides, because it will not work perfectly evenly.
Now we take the "zero" and under a stream of cold water we begin to clean the foil of the board blank from the oxide film. A sign of the absence of an oxide film is a uniform coating of the foil with a water layer and the absence of drops.
Now we separate the bottom (matte) film from the cut out piece of photoresist. This can be done with the tip of a cutter or with a needle. Separate the film approximately 5-10 mm wide and glue the photoresist to the workpiece so that there are no air bubbles.
Now gradually pulling out the film, roll the photoresist to the workpiece with a roller. After rolling, cut off the protruding sides and roll the workpiece in the laminator.
Now we proceed to the exposure (exposure) of the billet. I use a COMTECH CE ST 26 E27 BLACK lamp as a radiation source. At this stage, it is necessary to choose the right exposure time (see comments to the article). We put the workpiece on a hard, even surface, put a template on top and cover it all with ordinary window glass, and install a lamp on top.
We cover the workpiece with a book or other material that does not transmit light, turn on the lamp and let it warm up for a minute.
Remove the opaque coating and time it for normal exposure.
As soon as the time required for illumination has expired, turn off the lamp, remove the blank in a dark place and go to prepare the developer. As a developer I use soda ash (detergent), it is sold in household goods at a price of about 20 rubles per 0.5 kg. For cooking, take a teaspoon of baking soda and dilute with 1 glass of cold water.
Now we take out the illuminated workpiece, separate the upper glossy film, throw the workpiece into the developer and use three toothbrushes - a drawing of the future board begins to appear on the photoresist.
We continue to "clean" the future board until all the extra photoresist is washed off and we get this:
We wash our future board under cold water and throw it into the pickling solution to swim.
For etching, I use ferric chloride, and to speed up the process, I glue the board to a piece of foam with double-sided tape and lower it with the pattern down. In this case, it is necessary to check if air bubbles remain under the board, otherwise they will not stain. After 10 minutes, we get the following result:
Now you need to wash off the remaining photoresist and here you can go in 3 ways:
1) toss the board in caustic soda (CAUTION! ALKALI! WORK IN GLOVES!);
2) boil the board in the solution in which it was developed;
3) Throw the board into the solution in which the workpiece was developed.
The choice of method depends on the time it takes to make the payment. The longest is soaking in the solution in which it was developed (I throw it there overnight). Boiling in the developer takes about a couple of minutes. I don’t know the time for caustic soda, but they say that it is also very fast.
It remains to bring our board to the required size, tk. we made allowances on each side and we can drill and solder our device. But to give the board beauty and improve solderability, it is better to even tin the conductors. Someone with what, and I - with an alloy to Rose, as it turns out very quickly. For this I take the following ingredients:
Pour a glass of water into a bowl with a flat bottom and add a spoonful of citric acid (plays the role of a flux), throw the board there in the paths up and put a piece of Rose's alloy on top. We put all this on the stove and wait until the alloy begins to melt (it is better to hold the board with something).
The molten alloy is "rubbed over the board" (I use a brush with a piece of cotton wool wrapped around it). BE CAREFUL! STEAM CAN BURN YOUR HANDS! When rubbing, excess alloy is thrown into the water and only a thin shiny film remains on the conductors. We take out the board and rinse with water. Now you can drill and solder.
Some comments on technology:
1) The whole process takes about 1 hour.
2) When purchasing a photoresist, look at the manufacturing date. The shelf life is 9 months, after this period it does not stick well to the board. Store the purchased photoresist in a cold place (I have it in the refrigerator, it still sticks well, albeit expired).
3) You don't have a laminator to roll the photoresist to the workpiece? It doesn't matter - the iron will help. We turn on the thermostat to the 1st position and wait until the iron heats up. After heating to a certain temperature, the iron turns off, pull out the plug from the socket and put the board on the iron seam with the photoresist up, let the board warm up. We remove it and "from the heart" roll it with a roller.
4) When rolling the photoresist onto a wet workpiece and using a laminator, it is best to run the workpiece cold through the laminator to squeeze out the water. Otherwise, during hot lamination, water will evaporate and air bubbles will appear under the photoresist.
5) The choice of the exposure time of the workpiece through the template is as follows: A negative template with numbers from 1 to 10 is printed, applied to the board with the applied photoresist, and every minute the exposure is covered with an opaque material, one digit at a time, starting from 1. After development, you will see how many minutes light up. I have a 26W lamp, the distance from the workpiece to the lamp is 12 cm, the glass thickness is 4 mm - the exposure time is 3 minutes, I tried it for 5 minutes - it also works. I take a photoresist from the same manufacturer - const time.
6) Rosa can be tinned with an alloy in glycerin, but you can get it from your family for the "fog" in the kitchen.
7) When soldering a tinned board with flux, it must be washed off immediately after soldering, otherwise the flux causes darkening of the Rose alloy.
8) Photoresist is not afraid of light from incandescent lamps, so you can work with light.
We take a textolite with dimensions larger than the future board by 10 millimeters and clean it. For these purposes, I use a chrome washcloth.
The plus is that it removes the oxide layer while not picking up like sandpaper. Then we wipe it with alcohol, acetone, solvent or wash it with soap, it's to your taste, as you like. Personally, I use a brake cleaning spray.
Knurling. Here I will dwell on in more detail. I don't know if the photoresist is too good or too new, but if you apply it to copper, you won't be able to peel it off. Grabs to death. I made my first attempt like this. Tore off the protective film from the edge. This one is matte. Then he applied it to the copper with a corner and gradually, pressing it with his finger, pulled out the film. It stuck well, but there was dirt and bubbles ... In short, I switched to the principle of toners. We take a two vat syringe and fill it with plain, cold tap water. Then we tear off the protective film completely. We hold the photoresist with one hand, with the other we pour water from the syringe onto the copper. The syringe is more convenient, since the copper is defatted and the drops roll down, and the syringe dispenses a little over the entire copper. After wetting, apply a photoresist. While the copper is wet, the photoresist freely crawls over it, and the water pushes out all the debris and air. And even if something went wrong, you can always tear it off the copper. After fitting from the center to the edges, using a rubber spatula, without pressing, we expel the water. When all the water comes out, we begin to squeeze out the remnants with force, also from the center to the edges. The photoresist will start to knock closer to the edges. Nothing wrong. Pressing with a spatula from the center, it stretches quite easily and fits well.
After ironing, wipe it off with a napkin or toilet paper, it doesn't matter. The main thing is to wipe dry. We take a sheet of blank paper and fold it in half. Put textolite with photoresist between the halves and close this sandwich.
Well, here is someone like, someone with an iron, someone with a hairdryer, personally I am with a laminator. We heat the laminator at the highest temperature. After warming up, we send our sandwich there. Attention!!! If you send it to the laminator without a sheet of paper, then the pieces of photoresist, those that stick out outside the textolite, will be wrapped around the hot rolls and it will not be easy to tear it off from there.
I run it through the laminator twice in order to warm it up thoroughly. As a result, I get such a thing.
Template. There are three options here. The first is typography. Well, given her absence near my house, this option was immediately dropped. The second is printing on paper using a laser printer, then enlighten with transparency. Well, I don’t have this muck. And the last one is printing on film. The laser produced poor quality, or rather not bad, but rather transparent toner. Keep over acetone vapor ... No ice for two reasons. The first is that it stinks, and they will kick me out of the house, and the second is that now for some reason acetone has been replaced with some nasty thing that leaves drops of water after evaporation. Therefore, I switched to an inkjet. In addition, I have it sharpened for photos. The film "Lomond" was chosen for printing.
She has one drawback. The surface on which you need to print is rather sticky and any debris sticks to it, and this, as practice has shown, negatively affects the quality of the board. In short, if the distance between the tracks is 0.2 - 0.1 mm, then a speck of dust can play a bad role and create a gap between the tracks. Otherwise, this film makes great templates.
Oh yeah, I almost forgot. The template needs to be printed on the collar for eversion, that is, a negative. So where to etch the copper black, and where to leave it transparent. And don't forget to mirror. The important thing is that the paint should lie on the copper, and not vice versa, paint up. In general, we put the template on a photoresist and all this under a UV lamp. I have so:
Here we will dwell in more detail. Lamp: Model ELSM51B-Color 20W Black. As seen in the photo, energy saving. Purchased from "Chip-dip" for 200r. The distance from the lamp to the PCB is 20 cm. Taking into account that the glass retains UV light, it is impossible to specifically stipulate the exposure time, since someone will tear off 6 mm glass from the sideboard, someone 3 mm from the entrance window. I bought in "OBI" a photo-frame made of dense wood measuring 300 x 200. The pieces of iron and cardboard went straight to the trash heap, and the glass 2 mm thick went to the clamp. I used the frame itself to stretch the mesh for applying a solder mask. But this topic is another article. So I have 2 mm glass. For the cargo I use two 7 Ah gel batteries. In this form, the exposure is exactly two minutes from turning on the lamp to turning it off. I do not warm up the lamp, since 20 watts is quite powerful. As a result, I get an overexposed photoresist. Another plus against ours, after development, the exposed areas darken and you can see what happens. Next, we prepare the bath. On a glass COLD !!! water half a teaspoon of soda ash. The water should be at room temperature. If you take a hot one, it will be like with our photoresist. All the tracks will fall off. After preparing the bath, we bathe the textolite.
If you help with a brush, the development will take less than a minute. As a result, we will get just such beauty.
We dry, we look. If something is wrong somewhere, we will rule. If you can't fix it, then we start all over again. Another plus against our photoresist. After exposure, we throw it into the soda ash solution for 30 minutes and the photoresist will fall off by itself. Domestic so I could not tear off, neither acetone nor soda. In short, I threw out the spoiled workpieces. After all the checks, we poison in a pickling solution. Here every man for himself. Some in acid, some in vinegar, I personally prefer ferric chloride. Preferably water, otherwise waterless, if you throw it into the water, there will be an explosion :)
Well, after etching, as always, drilling and applying a solder mask, but this is the topic of the next article.
Like with a photoresist and that's it, if you have any questions, write either in the comments or on the forum.
All good boards.
Andrey 04/05/13
Great article. I did everything as written, it worked the first time. Now someone else would write the same article about metallization :)
SergeBS 04.21.13
Some kind of game. 1. "In short, if the distance between the tracks is 0.2 - 0.1 mm, then a speck of dust can play a bad role and create a jumper between the tracks." The photoresist is negative (see below about the template). The speck of dust will not let the track light up and, as a result, the track is broken and not closed. 2. "I use two 7 Ah helium batteries for the cargo." There is no HELIUM in the batteries, but there is GEL. And it is not at all necessary that there is gel in maintenance-free batteries. Gel batteries are rare. 3. "As a result, I get an overexposed photoresist. Another plus against our
SergeBS 04.21.13
Truncated comment. Okay. Let's repeat. Some kind of game. 3. "As a result, I get an overexposed photoresist. Another plus against ours, after development, the overexposed areas darken and you can look at what will turn out. Next, we prepare a bath. In a glass of COLD !!! water, half a teaspoon of soda ash. The water should be at room temperature. . If you take a hot one, it will be like with our photoresist. All the tracks will fall off. After preparing the bath, we bathe the textolite. If you help with a brush, the development will take no more than a minute. As a result, we are half
SergeBS 04.21.13
As a result, we will get this beauty. "We will not get NIFIGA. Before etching, you need to peel off the protective mylar film from the photoresist surface. Regardless of the origin of the film photoresist. (Import or Russia). So this is:" Andrey 05.04.13 Excellent article. Did everything as written, it turned out the first time. "Lies. Miracles do not happen, it does not etch through the film. And if you tear off the film before exposure, the photoresist will stick to the glass. 4." Dry, look. If something is wrong somewhere, we will rule. If you can't fix it, then we start all over again.
SergeBS 04.21.13
Great:). The photoresist flew off - pure copper remained - it's time to etch. Even if we assume a miracle that something (even soda, even ferric chloride) has crept through the unremoved protective film ... for the photoresist to fly off. About the explosion, a joke of humor, well, is completely out of place too. Someone can believe it. So this magnum opus must be edited. And in the future, do not write a review for yourself (this is about the mythical Andrey, who did as in the article and he succeeded :)). Read comments from bottom to top, "stitching" over identical pieces of text.
SergeBS 04.21.13
Total. CORRECT: 1. Negative template. You can use the laser. I have no inkjet - but everything is fine. 2. Peel off the bottom matte plastic wrap. 3. Glue and let lie under the load. 4. Highlighting - the template with paint (toner) to the photoresist.
SergeBS 04.21.13
5. After exposure - 30 minutes pause. Then we tear off the top shiny protective lavsan film and develop in baking soda. In a weak solution (citric acid - a teaspoon per glass) we tan the manifested. 6. In warm water we throw a little (so as not to boil) ferric chloride and poison in it.
SergeBS 04.21.13
7. Etched - in any alkali ("Mole" diluted 1:10 - 1:50 is that). In 10-15 minutes, the photoresist will fly off. 8. We wash with water (it is possible with liquid detergents). 9. We drill, tinker, solder the parts. All. In short, we do it according to the instructions ...
Alexey 04/21/13
Dear SergeBS 1 about the film. Describe its removal? Maybe you are offered to learn Russian, but how will you read an article, it is written in Russian. 2 With the battery, this is just a banter for the sake of writing. What's the difference than pressing. For example, I replaced them now with two trances. And that there are few photos in the article. By the way, this board works and feels great. And in the end there is a section "Write an article", you write, and you will be criticized, then we'll see. And everyone can shout and throw mud.
Alexey 04/21/13
Oh yes, at the expense of the laser. Neither XP nor Xerox provide quality templates. I've tried everything. Especially if with a domestic resist, then it is stupidly illuminated as if there is no template at all. Maybe, of course, they sold me an old resist ... And even if, according to your scheme, you tear off the protective film and try to glue it, and then under the load.)))) Well, well.
Vitaly 05/14/13
Alexey, a very wonderful article. I have a great desire to do all this, to begin with, buy everything you need (if you help with this I will be very grateful). And what kind of inkjet printer did you use.
Alexey 05/14/13
At first I had an Epson Stylus CX4300 but the head on it dried up. I have now bought an Epson L110. It is designed for continuous use and the ink is poured from the side into flasks, not cartridges. According to my measurements, black paint is enough for 50 sheets of A4 solid fill. And of course ink is much cheaper. If you have any questions, write. I will definitely answer.
Mikhail 05/16/13
Hello. The article is actually good, this is me, as a person who has been making boards for more than 15 years. SergeBS, why are you broke? Write your article, business. : +) And I have one question for the author: could you tell me what settings you set on the Epson L110 to print a template? Sincerely, Mikhail.
Alexey 05/16/13
Hello Mikhail. In the printer properties, select the "Advanced Settings" tab. In the "Color Correction" section, check the "Settings" box. The "Advanced ..." button will appear by clicking on which the settings menu will appear. In this menu, the brightness is at a minimum, and the contrast and saturation are at the maximum. Yellow at maximum (yellow delays UV) and magenta with cyan at minimum. And here's another, uncheck "High speed printing". Look like that's it.
Mikhail 05/16/13
What material / quality do you choose? In general, it's interesting, it's simple, I now also use the L100, and on the contrary I removed the yellow one, otherwise it refuses to dry on the template (the film is the same).
Alexey 05/16/13
And there the quality is either automatic or manual. My material is just paper. Do they dry for a long time? What ink? Relatives, "Fool" or not original? It is important.
Mikhail 05/16/13
I have a lot of everything in the drop-down list. Normal, High, Photo, Best Photo ... I am currently printing using Photo RPM (max dpi) with saturation up. Prints slowly, a bunch of passes, but the quality is perfect. Only here it is the yellow color that dries for a very long time. And the ink is native, which came in the kit.
Alexey 05/17/13
Well, in principle, this is the very thing. I set it up on the old one. How long do they dry? If about 10 minutes, then you can roll the photoresist at this time. :)
Alexey 11/22/13
For some reason, in the space between the 0.1 0.2 mm tracks, the photoresist in soda does not come off well .. you have to hold and help with a brush longer and at the moment when this space is cleared, in other places with thicker tracks there are already pads and the tracks themselves fly off ..
Alexey 11/23/13
Try reducing the exposure time by 10-15 seconds.
Alexey (friend 02/17/14
Hello Alexey! Thank you for the article. It's funny, but now I'm making exactly the same board for exactly the same controller, just not 100 but 103 series. I am suffering with PF-VShch. And my problems are exactly the same as you described. I have already taken out a sheet of 30x50 (my board is 5x6cm, i.e. about 50 samples), and the result is zero. I don’t give up yet. There is no other FR in our city. :(
Alexey 17.02.14
MarioFly 09/08/14
"Another plus against ours, after development, the exposed areas darken and you can see what happens." Not after development, but after exposure.
Anton 11/04/14
Yes, thanks, I also suffered with this PF-VShch. I thought that everything, my hands grew to another place. And yet I took Ordyl on trial, so everything worked out right away. Even with a pattern with gaps (LED printer), it came out normally at minimum illumination.
Alexey 11/04/14
I give this PF-VSH in good hands))) a roll of 5 meters. True, the expiration date has already expired, but I think it's nothing ... My protective mask has expired as 2 years and nothing. So if there are those who want to try their luck with PF-VShch, write. And then it's like a suitcase without a handle, you don't need nafik yourself, but it's a pity to throw it away.
Greetings, dear friends! You are on the blog of Vladimir Vasiliev and it is early morning outside! This is all because I got up early to write a useful post for you, so let's go ...
In the last article, I wrote that the quality of the boards received by LUT-m ceased to satisfy me, so I'm going to move away from the popular LUT technology and switch to photoresistive technology. For this I am including a film photoresist. By the way, it is quite possible that an article will soon appear on my blog on how to properly make printed circuit boards using the photoresist method. But it will be later, and now I want to tell you my experience of using a photoresist, in particular, getting the right exposure time.
There is one subtlety about using a photoresist. The quality of the formed pattern on the photoresist depends very much on the correctness of the selected exposure time (exposure). I felt this subtlety on myself.
After the photomask has been prepared and the photoresist is safely applied to the foil fiberglass, it is time to find out the required exposure time. For this I formed a "sandwich", covered the textolite with the applied photoresist with a photomask and put a sheet of plexiglass on top (in my case, it is a transparent cover from the CD box).
Next, a hypothetical exposure time of this sandwich was chosen - 2 minutes. For 2 minutes I turned on the ultraviolet lamp and began to wait with trepidation for the result. These 2 minutes passed quickly ... My first disappointment was that although I had an indicator photoresist, for some reason the purple outline of the drawing was extremely faded.
Well, further this beauty was expected by immersion in soda ash. The solution was a teaspoon of soda ash per liter of water. After washing in the solution, a second disappointment followed - if the pattern at the beginning of the washing still took place, then by the end of the washing (2-3 minutes) it was finally washed off. It's time to think ...
After analyzing my actions, I came to the conclusion that the weakest point in the chain of my actions was precisely the exposure time of the photoresist, and this time was insufficient ...
The exposure time cannot be somehow universal, because several floating factors appear here, including the quality of the photomask, the power of the UV lamp and its characteristics, the material of the pressure glass. All this can be very different and it is not surprising that when choosing one universal exposure time, the result will also be very different!
Based on the experience gained, I re-read a lot of information and found a very interesting trick with which you can quite accurately determine the required exposure time. I would like to note that this technique will only work when all these factors (UV lamp, photomask quality, pressure glass) are low.
In order to conduct this experiment and find out how long it takes to illuminate the photoresist, I suggest downloading the calibration photomask file. I found this file on one of the amateur radio forums. 
There is only a fragment of the picture in the image, if you download a pdf file then there will be 2 rows of ten images.
To conduct this experiment, you will need the following tools:
- Calibration drawing
- Installation for exposure (or just a UV lamp)
- A damper that is opaque to UV rays by the size of a photomask - it can be a strip of cardboard, opaque plastic, even a piece of PCB.
- Timer - the phone perfectly copes with the role of a timer
- Soda ash - sold in hardware stores and costs a penny
The essence of the experiment
We print our calibration drawing - this will be our photomask. Then we take our piece of foil-clad fiberglass with already knurled photoresist (if not already rolled, then roll it by running) and put it on the table with the photoresist up. Next, put the photomask with the printed side down, cover this bag with glass and press down well.
Weights can be used for these purposes, but I use paper clips. It should be noted that weights or clamps must not impede the movement of the valve. Yes, the next layer of our sandwich is a flap that should cover all the elements of the photomask except for the last one (for example, the 10th). One edge element of the photomask must remain open.
Thus, the nine elements will be closed by the shutter and therefore the UV rays from the lamp will not fall on them.
We place the Ultraviolet lamp above our composition at a distance of let's say 10 cm (at the moment this is not so important, but this moment can then be corrected according to the results of the experiment). We timed 5 minutes and turn on the UV lamp.
Every 30 seconds, we move the flap, thereby opening the next element of the picture. Thus, it turns out that the 10th element will receive the maximum exposure time, the 9th element will be exposed for 4 minutes 30 seconds, the 8th - 4 exactly, etc. The first element of the picture will glow for only 30 seconds.
After the end of the exposure, it becomes clear that the elements that were underexposed will appear the least. Elements that have received a sufficient dose of ultraviolet light will change their color to bright purple. At the same time, it should be noted that the areas of the picture covered by the photomask should not change their color. If this happens, it means that the pattern of the photomask is not dense enough and ultraviolet rays still fall on the photoresist. But even if your photomask is not perfect, all is not lost, you can find a compromise between underexposed and overexposed areas. But the final decision will be made only after the photoresist has developed.
Photoresist development
The photoresist development stage has come. To do this, we dilute about a teaspoon of soda ash in a liter of water and stir well. And now we put our illuminated sandwich in this bath.
During the development process, periodically pull the board out of the solution and rinse it in cold running water. In this case, the situation must be kept under control. It is necessary to wait for the moment when the protected elements (the elements that were covered with a photomask) finally dissolve in the solution, but the illuminated areas will be clear and contrasting. Thus, we find the element that suits us the most. And since we know how long each element shone, we can easily determine the required radiation dose.
For the purity of the experiment, it is worth repeating this procedure again and make sure that the result is repeatable.
After carrying out all this procedure, I found out that in my case the exposure time should be 4 minutes. Honestly, there were some flaws when applying a photomask. When the photomask was printed, it turned out to be surprisingly long (extended along the entire length of A4 sheet). It was me who later discovered that the drawing was printed at a scale of 212%. When overlapping, I had to limit myself to 5 elements from the photomask line, since the pressure glass could not cover the entire area.
Although the photo is not very high quality, you can see from the image that elements numbered 1 and 2 are faded more than elements numbered 3 and 4. The exposure time of elements 3 and 4 corresponds to 4 and 5 minutes, respectively. Yes, as you can see, I moved the shutter every minute, the wrong scale is to blame.
Well dear friends, that's all for me, I wish you success in all your endeavors and be positive! Be sure to subscribe to updates and see you soon!
Good day!
A small overview of LEDs that can be used to make printed circuit boards using a photoresist, as well as for etching a pattern on knives, hammers, etc.
(Alternative to UV lamp.)
There will be no ready-made printed circuit boards in the review, but there will be the results of several experiments, and an example of a finished device from these LEDs.
I decided to move from the method of making a printed circuit board using a marker to a more advanced method using a photoresist.
For those who are not familiar with this topic:
Briefly about the technology:
Photoresist - a light-sensitive material that reacts to light waves in a specific spectrum, in this case ultraviolet.
It is in the form of a film, in liquid form in an aerosol can, in a paste-like form, such as a solder mask.
Briefly about PCB manufacturing:
1 - We take a textolite covered with copper foil and apply a photoresist to it (in my case, a film);
2 - we make a photomask (we print on a printer on a transparent film or paper);
3 - we apply the template to the workpiece and shine with ultraviolet light;
4 - we develop in a developer solution (in my case, soda ash);
In places that are shaded by a template, the photoresist is washed off (or vice versa, it only remains there. Depends on the type of photoresist).
5 - we poison the board in a special solution.
In areas not covered with photoresist, the metal is eaten away, but remains under the photoresist layer, in accordance with the pattern of the photomask.
6 - wash off the photoresist.
The board is ready, you can tin-solder.
I will not write in more detail, here is clearer:
Other metal objects:
I did not find an ultraviolet lamp offline, and the cost of an order in our online stores, taking into account delivery, was close to 500 rubles, so it was decided to order a couple of hundred UV LEDs in China to make a matrix from them. For the money, it turned out about the same for the same, but the use of LEDs, in my opinion, has several advantages:
More directed light flux, more powerful (because it shines in one direction, and not everywhere and around like a lamp), which means less side illumination and shorter exposure time,
- stronger than a fragile glass lamp.
At the time of ordering, this lot was one of the cheapest. The seller almost always has a discount on this product, so if you don't see it, I advise you to wait until he puts it back.
So. I ordered it at the end of November, received it at the beginning of January.
200 LEDs were ordered, and so many have come.
I can't remember how the whole order was packed, but every hundred LEDs were packed in an antistatic bag.
This is how one LED shines:
How ultraviolet it is and what the spectrum of its radiation is, I do not know. But it works the way I need it.
The LEDs were installed on a plexiglass panel in holes 5 mm in diameter, fixed with hot melt glue. 12 rows of 16 LEDs, 192 pcs. Total. The distance between the centers of the holes is 12.5 mm. The result is a rectangular area of \u200b\u200b150 x 200 (mm).
LEDs have a diameter of ~ 5 mm near the skirt, from the side of the "lens" the diameter is slightly less than ~ 4.5 mm, along the side ~ 5.5 mm. The LED is inserted up to the stop with its rim into the surface of the panel, which allows it to be installed perpendicular to its surface.
However, not in all LEDs the crystal is located strictly on the optical axis of the lens.
I made the case, soldered it and it turned out like this:
It was experimentally found that the operating voltage of these LEDs is 3.2 V, the spread between different copies is small.
The seller declares an operating current of 20 mA.
The entire matrix is \u200b\u200bpowered by 12V. LEDs are connected in groups of 3. plus a 120 ohm limiting resistor.
There are 64 groups in total. And the estimated total current is 1.28 A.
After I purchased all the parts, I realized that it would be good to limit the current below 20 mA - who knows how much the seller's description corresponds to reality? I wanted to connect the matrix through a diode so that some voltage would drop on it and the current would be less, but it turned out that the voltage on the power supply dedicated for working with this design sinks to 11.6 V under load, and the operating current is ~ 16.6 mA. So he left it.
For better cooling of the LEDs, I did not shorten their legs. I did not notice any strong heating of the diodes, the panel with the diodes itself is a little warm, and the case is cold. True, the device did not turn on for more than 10 minutes.
I took several photos to assess the uniformity of lighting (but I forgot to set manual settings and clicked everything automatically, corrected it a little in the editor):
The rectangle drawn on A4 sheet has dimensions of 200x150 (mm).
Distance from matrix to paper ~ 12 cm.
Mastering the whole process was carried out using a test template. The template was drawn in a graphic editor and printed on a transparent film by a laser printer (link to the template at the end of the review). The thinnest lines on the template were to be 0.1 mm. But for a printer, it turned out to be too tough to print such a template - several lines of 0.1 mm merged into one, and the size of the thicker lines must have gone a little. I have nothing to assess the quality of the template, I am content with what I have.
Used photoresist Ardyl Alpha 340, film negative.
Before applying the film, I cleaned the board with a sponge for dishes (two-layer), a hard layer with detergent. Degreased with isopropyl alcohol.
Pasted on "dry", "burned" with a hair dryer.
The template was attached to the workpiece with tape, and it was pressed against a layer of water.
Here are the results I have achieved:
The exposure time was 20 seconds.
The numbers on the right are the thickness of the tracks, the distance between them is the same (calculated, without taking into account the accuracy of the printer).
It can be seen that in one place there is a jumper between the two lines - most likely a speck of dust has hit. Yes, such a trifle, next time I will try to stick the photoresist under running water.
Above, I have given the best result that I could achieve.
And it shows what you can count on using a photoresist.
More examples of my experiments are available here -.
In them, what was obtained with exposure from different distances from the workpiece and with different values \u200b\u200bof exposure time.
Since I am not currently collecting any device, I publish only these results in the review. And if you wait until I collect something, then the probability increases that the seller will send the goods from a completely different batch.
What can I say? I am satisfied with the product. I recommend it for purchase.
Despite the low cost of LEDs, it’s hardly possible to save money here - the cost of LEDs plus the cost of other materials will most likely be comparable to the cost of an ultraviolet lamp and delivery (as in my case). Yes, and fiddles with all this still. I did this device for two weeks, in the evenings after work and other things.
It's easier with a lamp - you bought it, screwed it in (if there is any) and use it. It takes up less space.
Well, if you do not consider the manufacture of such a "chandelier" from lamps.
But the exposure time when using diodes is noticeably shorter. And if, when the photoresist is illuminated, the difference may not be significant, then when the mask is illuminated, this difference should be more noticeable (as far as I know, I have not tried to light the mask much longer than the photoresist).
What was used:
Xerox 3010 printer (new toner cartridge);
- film photoresist Ordyl Alpha 340;
- transparent film Lomond 0701415;
- developer - soda ash;
- pickling solution - citric acid with peroxide.
Well, like everything I wanted to tell.
UPD: To reduce side illumination, I took thicker plexiglass (5 mm, I don’t have a thicker one) to remove light from the middle part of the LED, and painted the outside with black paint.
UPD_2: I didn't bite off the legs of the LEDs for better cooling - they will last longer.
UPD_3: I did not use LED strips due to the fact that diodes with a wide scattering angle are installed on them - the side illumination will be greater than that of the observed ones. In any case, I have not seen other tapes.
I plan to buy +63 Add to favorites Review liked +83 +146