How to make a drawing of a printed circuit board. Etching circuit boards with hydrogen peroxide and citric acid
After drawing printed circuit board transferred to foil PCB using , it is necessary to etch the printed circuit board. Several recipes for etching printed circuit boards are described under the cut.
1. Method one - ferric chloride.
Add ferric chloride to water in a ratio of 1:3. To stir thoroughly.
The etching time depends on the temperature of the solution, the thickness of the copper and the “freshness” of the solution.
On average from 10 minutes to an hour. When applying tracks with laser printer toner, do not heat it above 45°C.
It is recommended to rock the board in the solution.
2. Method two - copper sulfate plus table salt.
Preparation of solution - 200 ml. warm water two tablespoons of table salt and a tablespoon of copper sulfate. The etching process can be quite lengthy.
Salt
For the etching process to proceed normally, it is recommended to use a significant excess of salt, heat the solution and rock the board in the solution.
3. Etching the printed circuit board in hydrogen peroxide plus citric acid.
Enough quick way etching of the printed circuit board at room temperature plus the availability of components.
Solution composition:
In 100 ml. Dissolve 3% hydrogen peroxide with 30 g of citric acid and 5 g of table salt.
Salt can be given in excess.
The solution should not be diluted. The more peroxide, the more intense the process will be.
But we must take into account that the solution is disposable and cannot be stored.
Someone might say, I’m happy with persulfate because of its etching speed, but the new etching method makes it possible to etch boards, I think, at no less speed. Yesterday I etched the board in half an hour, the design was quickly drawn with a marker, the narrowest paths were 1 mm wide, no undercuts were noticed. The photo of the board is below, though after I tinned and soldered all the parts onto the board, just to show that even narrow traces are obtained without undercuts, I think this is enough. But I would like to immediately note that the drawing transferred to the printed circuit board using the LUT (laser ironing technology) is preserved better; according to people’s reviews, when etching with this method, even narrow paths 1 mm wide turn out consistently well.
Now let's get down to business. For the board measuring 35*25, which I etched, I used the following ingredients: bottle of pharmaceutical hydrogen peroxide 50 ml, cost 3 rubles and 1 sachet of 10 grams food grade citric acid, costing 3.5 rubles, salt teaspoon(used as a catalyst) of course free of charge, any you have in your kitchen will do, even iodized one. Exact proportions are not necessary here; we make something like this: pour in enough hydrogen peroxide to cover the board by 5 mm, add 10 grams (in my case a bag) of citric acid and add a teaspoon of salt .
There is no need to add water, the liquid that is in the peroxide is used. If you plan to etch the board large sizes, then we increase the amount of ingredients in those proportions relative to hydrogen peroxide, as indicated above, also so that the board is hidden by 5 mm. By the end of etching, the solution will turn bluish. During etching, we move the board in the container, because gas bubbles will accumulate on the board, interfering with etching.
Towards the end of etching, remove the board from the solution with tweezers and inspect it. If we draw a picture with a marker, I recommend drawing in several layers to avoid small undercuts on narrow paths, but ferric chloride and ammonium persulfate will give us the same effect. The remaining solution from etching can be poured down the drain, followed by a large amount of water. Store the solution for reuse, I don’t think anyone will, it’s always easier to make a new solution if necessary than to wait longer when etching with an old solution.
Saving time and money compared to old methods is obvious to everyone, I think. You can also use concentrated peroxide sold in hairdressing stores or hydroperite tablets, but here everyone will have to choose the ratio of ingredients themselves, since I haven’t experimented with them. As promised, I’m posting a photo of the board etched using this method; I made the board in a hurry, though.
A little more about this one useful thing, How vertical baths. If uniform and high-quality double-sided etching is required, vertical baths with solution mixing are convenient. Stirring is done by introducing a tube from an aquarium aerator into the bath. Also, a vertical bath has a minimal evaporation area. In addition, there will be no sticking dirt if the solution is old and littered. I wish you successful etching without any undercuts. I was with you AKV .
Discuss the article ETCHING PRINTED BOARDS
Today we will speak in a slightly unusual role; we will talk not about gadgets, but about the technologies that lie behind them. A month ago we were in Kazan, where we met the guys from Navigator Campus. At the same time, we visited a nearby (well, relatively close) factory for the production of printed circuit boards - Technotech. This post is an attempt to understand how those same printed circuit boards are produced.
So, how are printed circuit boards made for our favorite gadgets?
The factory knows how to make boards from start to finish - designing a board according to your technical specifications, manufacturing fiberglass laminate, producing single-sided and double-sided printed circuit boards, producing multilayer printed circuit boards, marking, testing, manual and automatic assembly and soldering of boards.
First, I'll show you how double-sided boards are made. Their technical process is no different from the production of single-sided printed circuit boards, except that during the manufacture of OPP they do not perform operations on the second side.
About board manufacturing methods
In general, all methods of manufacturing printed circuit boards can be divided into two large categories: additive (from the Latin additio-adding) and subtractive (from Latin subtratio-subtraction). An example of subtractive technology is the well-known LUT (Laser Ironing Technology) and its variations. In the process of creating a printed circuit board using this technology, we protect future tracks on a sheet of fiberglass with toner from a laser printer, and then bleed off everything unnecessary in ferric chloride. In additive methods, on the contrary, conductive tracks are deposited on the surface of the dielectric in one way or another.
Semi-additive methods (sometimes also called combined) are a cross between classical additive and subtractive. During the production of PCBs using this method, part of the conductive coating may be etched off (sometimes almost immediately after application), but as a rule this happens faster/easier/cheaper than in subtractive methods. In most cases, this is a consequence of the fact that most of the track thickness is increased by electroplating or chemical methods, and the layer that is etched is thin and serves only as a conductive coating for electroplating.
I will show you exactly the combined method.
Manufacturing of two-layer printed circuit boards using the combined positive method (semi-additive method)
Manufacturing of fiberglass laminate
The process begins with the manufacture of foil fiberglass laminate. Fiberglass is a material consisting of thin sheets of fiberglass (they look like dense shiny fabric), impregnated epoxy resin and pressed in a stack into a sheet. The fiberglass sheets themselves are also not very simple - they are woven (like ordinary fabric in your shirt) thin, thin threads of ordinary glass. They are so thin that they can easily bend in any direction. It looks something like this:
You can see the orientation of the fibers in the long-suffering picture from Wikipedia:
In the center of the board, the light areas are the fibers running perpendicular to the cut, the slightly darker areas are parallel.
Or for example on a microphotograph of tiberius, as far as I remember from this article:
So, let's begin.
Fiberglass fabric is supplied to production in the following reels: 
It is already impregnated with partially cured epoxy resin - this material is called prepreg, from English pre-im preg nated - pre-impregnated. Since the resin is already partially cured, it is no longer as sticky as in liquid state- the sheets can be taken by hand without any fear of getting dirty with resin. The resin will only become liquid when the foil is heated, and then only for a few minutes before completely solidifying.
The required number of layers along with copper foil is assembled on this machine: 
And here is the roll of foil itself. 
Next, the canvas is cut into pieces and fed into a press with a height of two human heights: 
In the photo is Vladimir Potapenko, production manager.
The technology of heating during pressing is implemented in an interesting way: not parts of the press are heated, but the foil itself. A current is supplied to both sides of the sheet, which, due to the resistance of the foil, heats the sheet of future fiberglass. Pressing occurs at very low pressure to prevent the appearance of air bubbles inside the PCB 
When pressed, due to heat and pressure, the resin softens, fills the voids, and after polymerization, a single sheet is obtained.
Like this: 
It is cut into blanks for circuit boards using a special machine: 
Technotech uses two types of blanks: 305x450 - small group blank, 457x610 - large blank
After this, a route map is printed for each set of blanks, and the journey begins... 
A route card is a piece of paper with a list of operations, information about the fee and a barcode. To control the execution of operations, 1C 8 is used, which contains all the information about orders, the technical process, and so on. After completing the next production stage, the barcode on the route sheet is scanned and entered into the database.
Drilling blanks
The first step in the production of single-layer and double-layer printed circuit boards is drilling holes. With multilayer boards it's more complicated, and I'll talk about that later. Blanks with route sheets arrive at the drilling section: 
A package for drilling is assembled from the blanks. It consists of a substrate (plywood type material), from one to three identical printed circuit board blanks and aluminum foil. The foil is needed to determine whether the drill is touching the surface of the workpiece - this is how the machine determines whether the drill is broken. Every time he grabs the drill, he controls its length and sharpening with a laser.
After assembling the package, it is placed in this machine:
It is so long that I had to stitch this photo together from several frames. This is a Swiss machine from Posalux, unfortunately I don’t know the exact model. In terms of characteristics, it is close to this. It consumes three times three-phase power supply voltage of 400V, and consumes 20 kW during operation. The weight of the machine is about 8 tons. It can simultaneously process four packages using different programs, which gives a total of 12 boards per cycle (naturally, all workpieces in one package will be drilled the same way). The drilling cycle ranges from 5 minutes to several hours, depending on the complexity and number of holes. Average time is about 20 minutes. Technotech has three such machines in total.
The program is developed separately and downloaded over the network. All the operator needs to do is scan the batch barcode and place the package of blanks inside. Tool magazine capacity: 6000 drills or cutters.
Nearby there is a large cabinet with drills, but the operator does not need to control the sharpening of each drill and change it - the machine always knows the degree of wear of the drills - it records in its memory how many holes were drilled by each drill. When the resource is exhausted, he himself replaces the drill with a new one, the old drills will only have to be unloaded from the container and sent for re-sharpening.
This is what the inside of the machine looks like:
After drilling, a mark is made in the route sheet and base, and the board is sent stage by stage to the next stage.
Cleaning, activation of workpieces and chemical copper plating.
Although the machine uses its own “vacuum cleaner” during and after drilling, the surface of the board and holes still needs to be cleaned of dirt and prepared for the next technological operation. To begin with, the board is simply cleaned in a cleaning solution with mechanical abrasives 
Inscriptions, from left to right: “Brush cleaning chamber top/bottom”, “Washing chamber”, “Neutral zone”.
The board becomes clean and shiny:
After this, the surface activation process is carried out in a similar installation. A serial number is entered for each surface. Surface activation is the preparation for deposition of copper onto the inner surface of the holes to create vias between the layers of the board. Copper cannot settle on an unprepared surface, so the board is treated with special palladium-based catalysts. Palladium, unlike copper, is easily deposited on any surface, and subsequently serves as crystallization centers for copper. Activation installation:
After this, successively passing through several baths in another similar installation, the workpiece acquires a thin (less than a micron) layer of copper in the holes. 
Then this layer is increased by galvanization to 3-5 microns - this improves the layer’s resistance to oxidation and damage.
Application and exposure of photoresist, removal of unexposed areas.
Next, the board is sent to the photoresist application area. They didn’t let us in there because it was closed, and in general, it was a clean room, so we’ll limit ourselves to photographs through the glass. I saw something similar in Half-Life (I'm talking about pipes coming down from the ceiling): 
Actually, the green film on the drum is the photoresist.
Next, from left to right (in the first photo): two installations for applying photoresist, then an automatic and manual frame for illumination using pre-prepared photo templates. The automatic frame has a control that takes into account alignment tolerances with reference points and holes. IN hand framed The mask and the board are combined by hand. Silk-screen printing and solder mask are displayed on the same frames. Next is the installation of developing and washing the boards, but since we didn’t get there, I don’t have photos of this part. But there is nothing interesting there - approximately the same conveyor as in “activation”, where the workpiece passes successively through several baths with different solutions.
And in the foreground is a huge printer that prints these same photo templates:
Here is the board with it applied, exposed and developed:
Please note that photoresist is applied to areas where later will not copper - the mask is negative, not positive, as in LUT or homemade photoresist. This is because in the future the build-up will occur in the areas of future tracks.
This is also a positive mask:
All these operations take place under non-actinic lighting, the spectrum of which is selected in such a way as to simultaneously not affect the photoresist and provide maximum illumination for human work in a given room.
I love announcements whose meaning I don’t understand:
Galvanic metallization
Now it has come through Her Majesty - galvanic metallization. In fact, it was already carried out at the previous stage, when a thin layer of chemical copper was built up. But now the layer will be increased even more - from 3 microns to 25. This is the layer that conducts the main current in the vias. This is done in the following baths: 
In which complex compositions of electrolytes circulate:
And a special robot, obeying the programmed program, drags boards from one bath to another:
One copper plating cycle takes 1 hour 40 minutes. One pallet can process 4 workpieces, but there can be several such pallets in a bath.
Deposition of metal resist
The next operation is another galvanic metallization, only now the deposited material is not copper, but POS - lead-tin solder. And the coating itself, by analogy with photoresist, is called metal resist. The boards are installed in the frame: 
This frame goes through several already familiar galvanic baths:
And it is covered with a white layer of POS. In the background you can see another board, not yet processed:
Photoresist removal, copper etching, metal resist removal
Now the photoresist is washed off from the boards, it has fulfilled its function. Now for still copper board There were tracks covered with metal resist. At this installation, etching occurs in a tricky solution that etches the copper, but does not touch the metal resist. As far as I remember, it consists of ammonium carbonate, ammonium chloride and ammonium hydroxide. After etching, the boards look like this:
The tracks on the board are a “sandwich” of the bottom layer of copper and the top layer of galvanic POS. Now, with another even more cunning solution, another operation is carried out - the POS layer is removed without affecting the copper layer.
True, sometimes the PIC is not removed, but is melted in special furnaces. Or the board goes through hot tinning (HASL process) - where it is lowered into a large bath of solder. First, it is coated with rosin flux:
And it is installed in this machine:
He lowers the board into the solder bath and immediately pulls it back out. Air currents blow away excess solder, leaving only a thin layer on the board. The payment is like this:
But in fact, the method is a little “barbaric” and does not work very well on boards, especially multilayer ones - when immersed in molten solder, the board suffers a temperature shock, which does not work very well on the internal elements of multilayer boards and thin traces of single- and double-layer boards.
It is much better to cover with immersion gold or silver. Here is some very good information on immersion coatings if anyone is interested.
We did not visit the immersion coating site for a banal reason - it was closed, and we were too lazy to get the key. It's a pity.
Electrotest
Next, the almost finished boards are sent for visual inspection and electrical testing. An electrical test is when the connections of all contact pads are checked to see if there are any breaks. It looks very funny - the machine holds the board and quickly pokes probes into it. You can watch a video of this process on my Instagram(by the way, you can subscribe there). And in photo form it looks like this: 
That big machine on the left is the electrical test. And here are the probes themselves closer:
In the video, however, there was another machine - with 4 probes, but here there are 16 of them. They say it is much faster than all three old machines with four probes combined.
Solder mask application and pad coating
The next technological process is applying a solder mask. That same green (well, most often green. But in general it can be very different colors) coating that we see on the surface of the boards. Prepared boards: 
They are put into this machine:
Which, through a thin mesh, spreads a semi-liquid mask over the surface of the board:
By the way, the application video can also be viewed in Instagram(and subscribe too:)
After this, the boards are dried until the mask stops sticking, and are exposed in the same yellow room that we saw above. After this, the unexposed mask is washed off, exposing the contact patches:
Then they are covered finishing coat- hot tinning or immersion coating:
And markings are applied - silk-screen printing. These are white (most often) letters that show where which connector is and which element is located there.
It can be applied using two technologies. In the first case, everything happens the same as with a solder mask, only the color of the composition differs. It covers the entire surface of the board, then it is exposed, and the areas not cured by ultraviolet light are washed off. In the second case, it is applied by a special printer that prints with a tricky epoxy compound:
It's both cheaper and much faster. The military, by the way, does not favor this printer, and constantly states in the requirements for their boards that markings are applied only with photopolymer, which greatly upsets the chief technologist.
Manufacturing of multilayer printed circuit boards using the through-hole metallization method:
Everything that I described above applies only to single-sided and double-sided printed circuit boards (at the factory, by the way, no one calls them that, everyone says OPP and DPP). Multilayer boards (MPCs) are made on the same equipment, but using a slightly different technology. Manufacturing of kernels
The core is an inner layer of thin PCB with copper conductors on it. There can be from 1 such cores in a board (plus two sides - a three-layer board) to 20. One of the cores is called gold - this means that it is used as a reference - the layer on which all the others are set. The kernels look like this: 
They are made in exactly the same way as conventional boards, only the thickness of the fiberglass laminate is very small - usually 0.5 mm. The sheet turns out so thin that it can be bent like thick paper. Copper foil is applied to its surface, and then all the usual stages occur - application, photoresist exposure and etching. The result of this is the following sheets:
After manufacturing, the tracks are checked for integrity on a machine that compares the board pattern against the light with a photomask. In addition, there is also visual control. And it’s really visual - people sit and look at the blanks:
Sometimes one of the control stages makes a verdict about poor quality one of the blanks (black crosses):
This sheet of boards, in which a defect occurred, will still be manufactured in full, but after cutting, the defective board will go into the trash. After all layers are made and tested, the next technological operation begins.
Assembling kernels into a bag and pressing
This happens in a room called the “Pressing Area”: 
The cores for the board are laid out in this pile:
And next to it is a map of the location of the layers:
After which a semi-automatic board pressing machine comes into play. Its semi-automatic nature lies in the fact that the operator must, at her command, give her the kernels in a certain order.
Transferring them for insulation and gluing with prepreg sheets:
And then the magic begins. The machine grabs and transfers sheets to the working field:
And then he aligns them along the reference holes relative to the gold layer.
Next, the workpiece enters hot press, and after heating and polymerization of the layers - into a cold one. After this, we receive the same sheet of fiberglass, which is no different from blanks for two-layer printed circuit boards. But inside it has a good heart, several cores with formed tracks, which, however, are not yet connected in any way and are separated by insulating layers of polymerized prepreg. Then the process goes through the same stages that I described earlier. True, with a slight difference.
Drilling blanks
When assembling a package of OPP and DPP for drilling, it does not need to be centered, and it can be assembled with some tolerance - this is still the first technological operation, and all others will be guided by it. But when assembling a package of multilayer printed circuit boards, it is very important to adhere to the internal layers - when drilling, the hole must pass through all the internal contacts of the cores, connecting them in ecstasy during metallization. Therefore, the package is assembled on a machine like this: 
It's x-ray drilling machine, which sees through the textolite internal metal reference marks and, based on their location, drills basic holes into which fasteners are inserted for installing the package into a drilling machine.
Metallization
Then everything is simple - the workpieces are drilled, cleaned, activated and metallized. The metallization of the hole connects all the copper heels inside the printed circuit board: 
Thus, completing electronic circuit the insides of the printed circuit board.
Checking and polishing
Next, a piece is cut from each board, which is polished and examined under a microscope to make sure that all the holes turned out fine. 
These pieces are called sections - transversely cut parts of the printed circuit board, which allows you to evaluate the quality of the board as a whole and the thickness of the copper layer in the central layers and vias. IN in this case, it is not a separate board that is allowed for grinding, but the entire set of via diameters specially made from the edge of the board that are used in the order. A thin section filled in transparent plastic looks like this:
Milling or scribing
Next, the boards that are on the group blank must be divided into several parts. This is done either on a milling machine: 
Which cuts out the desired contour with a milling cutter. Another option is scribing, this is when the outline of the board is not cut out, but cut with a round knife. This is faster and cheaper, but allows you to make only rectangular boards, without complex contours and internal cutouts. Here is the scribed board:
And here is the milled one:
If only the production of boards was ordered, then it all ends there - the boards are put in a pile:
It turns into the same route sheet:
And waiting to be sent.
And if you need assembly and sealing, then there is still something interesting ahead.
Assembly
Then the board, if necessary, goes to the assembly area, where the necessary components are soldered onto it. If we are talking about manual assembly, then everything is clear, there are people sitting (by the way, most of them are women, when I went to them, my ears curled up from the song from the tape recorder “God, what a man”):
And they collect, they collect:
But if we talk about automatic assembly, then everything is much more interesting. This happens on such a long 10-meter installation, which does everything - from applying solder paste to soldering on thermal profiles.
By the way, everything is serious. Even the rugs are grounded there:
As I said, it all starts with the fact that an uncut sheet with printed circuit boards is installed together with a metal template at the beginning of the machine. Thickly spread onto the template solder paste, and the squeegee knife passing from above leaves precisely measured amounts of paste in the recesses of the template.
The template is raised and the solder paste is placed in the correct places on the board. Cassettes with components are installed in the following compartments:
Each component is inserted into its corresponding cassette:
The computer that controls the machine is told where each component is located:
And he begins to arrange components on the board.
It looks like this (video not mine). You can watch forever:
The component installation machine is called Yamaha YS100 and is capable of installing 25,000 components per hour (one takes 0.14 seconds).
Then the board passes through the hot and cold zones of the stove (cold means “only” 140°C, compared to 300°C in the hot part). Having spent a strictly defined time in each zone with a strictly defined temperature, the solder paste melts, forming one whole with the legs of the elements and the printed circuit board:
The soldered sheet of boards looks like this:
All. The board is cut, if necessary, and packaged to soon go to the customer:
Examples
Finally, examples of what technotech can do. For example, the design and manufacture of multilayer boards (up to 20 layers), including boards for BGA components and HDI boards: 
C with all “numbered” military approvals (yes, each board is manually marked with a number and production date - this is required by the military):
Design, manufacturing and assembly of boards of almost any complexity, from our own or from customer components:
And HF, microwave, boards with a metalized end and a metal base (I didn’t take photos of this, unfortunately).
Of course, they are not a competitor to Resonit in terms of quick prototypes of boards, but if you have 5 or more pieces, I recommend asking them for the cost of production - they really want to work with civilian orders.
And yet, there is still production in Russia. No matter what they say.
Finally, you can catch your breath, look up at the ceiling and try to understand the intricacies of the pipes: 
I don’t know about you, but I have a fierce hatred for classic circuit boards. The installation is such a crap with holes where you can insert parts and solder them, where all connections are made through wiring. It seems simple, but it turns out to be such a mess that understanding anything in it is very problematic. Therefore, there are errors and burnt parts, incomprehensible glitches. Well, screw her. Just spoil your nerves. It’s much easier for me to draw a circuit in my favorite one and immediately etch it in the form of a printed circuit board. Using laser-iron method everything comes out in about an hour and a half of easy work. And, of course, this method is excellent for making the final device, since the quality of printed circuit boards obtained by this method is very high. And since this method is very difficult for the inexperienced, I will be happy to share my proven technology, which allows you to get printed circuit boards the first time and without any stress with tracks 0.3mm and clearance between them up to 0.2mm. As an example, I will make a development board for my training course dedicated to the controller AVR. You will find the principle in the entry, and
There is a demo circuit on the board, as well as a bunch of copper patches, which can also be drilled out and used for your needs, like a regular circuit board.
▌Technology for manufacturing high-quality printed circuit boards at home.
The essence of the method of manufacturing printed circuit boards is that a protective pattern is applied to the foil-coated PCB, which prevents etching of copper. As a result, after etching, traces of conductors remain on the board. There are many ways to apply protective patterns. Previously, they were painted with nitro paint using a glass tube, then they began to be applied with waterproof markers or even cut out of tape and pasted onto the board. Also available for amateur use photoresist, which is applied to the board and then illuminated. The exposed areas become soluble in alkali and are washed off. But in terms of ease of use, cheapness and speed of production, all these methods are much inferior laser-iron method(Further LUT).
The LUT method is based on the fact that a protective pattern is formed by toner, which is transferred to the PCB by heating.
So we will need a laser printer, since they are not uncommon now. I use a printer Samsung ML1520 with original cartridge. Refilled cartridges fit extremely poorly, as they lack density and uniformity of toner dispensing. In the print properties, you need to set the maximum toner density and contrast, and be sure to disable all saving modes - this is not the case.
▌Tools and materials
In addition to foil PCB, we also need a laser printer, an iron, photo paper, acetone, fine sandpaper, a suede brush with metal-plastic bristles,
▌Process
Next, we draw a drawing of the board in any software convenient for us and print it. Sprint Layout. A simple drawing tool for circuit boards. To print normally, you need to set the layer colors on the left to black. Otherwise it will turn out to be garbage.
Printing, two copies. You never know, maybe we'll screw one up.
This is where the main subtlety of the technology lies LUT because of which many people have problems getting out quality boards and they give it up. Through many experiments, it was found that the best results are achieved when printing on glossy photo paper for inkjet printers. I would call photo paper ideal LOMOND 120g/m2
It is inexpensive, sold everywhere, and most importantly it gives an excellent and repeatable result, and its glossy layer does not stick to the printer’s stove. This is very important, since I have heard about cases where glossy paper was used to dirty the printer oven.
We load the paper into the printer and confidently print on the glossy side. You need to print in a mirror image so that after transfer the picture corresponds to reality. I can’t count how many times I made mistakes and made incorrect prints :) Therefore, for the first time, it’s better to print on plain paper for a test and check that everything is correct. At the same time, you will warm up the printer oven.
After printing the picture, in no case Do not grab with your hands and preferably keep away from dust. So that nothing interferes with the contact of the toner and copper. Next, we cut out the board pattern exactly along the contour. Without any reserves - the paper is hard, so everything will be fine.
Now let's deal with the textolite. Let's cut a piece right away the right size, without tolerances and allowances. As much as needs.
It needs to be sanded well. Carefully, trying to remove all the oxide, preferably in a circular motion. A little roughness won't hurt - the toner will stick better. You can use an “effect” abrasive sponge instead of sandpaper. You just need to take a new one, not greasy.
It’s better to take the smallest skin you can find. I have this one.
After sanding, it must be thoroughly degreased. I usually use my wife’s cotton pad and, after moistening it thoroughly with acetone, I thoroughly go over the entire surface. Again, after degreasing, you should never grab it with your fingers.
We put our drawing on the board, naturally with the toner down. Warming up iron to maximum, holding the paper with your finger, firmly press and iron one half. The toner needs to stick to the copper.
Next, without allowing the paper to move, iron the entire surface. We press with all our might, polish and iron the board. Trying not to miss a single millimeter of the surface. This is a most important operation; the quality of the entire board depends on it. Don’t be afraid to press as hard as you can; the toner won’t float or smear, since the photo paper is thick and perfectly protects it from spreading.
Iron until the paper turns yellow. However, this depends on the temperature of the iron. My new iron hardly turns yellow, but my old one almost charred - the result was equally good everywhere.
Afterwards you can let the board cool down a bit. And then, grabbing it with tweezers, we put it under water. And we keep it in the water for some time, usually about two to three minutes.
Taking a suede brush, under a strong stream of water, we begin to violently lift the outer surface of the paper. We need to cover it with multiple scratches so that the water penetrates deep into the paper. In confirmation of your actions, the drawing will be shown through thick paper.
And with this brush we brush the board until we remove the top layer.
When the entire design is clearly visible, without white spots, you can begin to carefully roll the paper from the center to the edges. Paper Lomond Rolls out beautifully, leaving 100% toner and pure copper almost immediately.
Having rolled out the entire pattern with your fingers, you can thoroughly scrub the entire board with a toothbrush to clean out the remaining glossy layer and scraps of paper. Don’t be afraid, it’s almost impossible to remove well-cooked toner with a toothbrush.
We wipe the board and let it dry. When the toner dries and turns gray, it will be clearly visible where the paper remains and where everything is clean. The whitish films between the tracks must be removed. You can destroy them with a needle, or you can rub them with a toothbrush under running water. In general, it is useful to walk along the paths with a brush. The whitish gloss can be pulled out of narrow cracks using electrical tape or masking tape. It doesn't stick as violently as usual and doesn't strip off the toner. But the remaining gloss comes off without a trace and immediately.
Under the light of a bright lamp, carefully examine the toner layers for tears. The fact is that when it cools, it can crack, then a narrow crack will remain in this place. Under the light of the lamp, the cracks sparkle. These areas should be touched up with a permanent marker for CDs. Even if there is only a suspicion, it is still better to paint over it. The same marker can also be used to fill in poor-quality paths, if any. I recommend a marker Centropen 2846- it gives a thick layer of paint and, in fact, you can stupidly paint paths with it.
When the board is ready, you can water the ferric chloride solution.
Technical digression, you can skip it if you wish.
In general, you can poison a lot of things. Someone is poisoning copper sulfate, some are in acidic solutions, and I am in ferric chloride. Because It is sold in any radio store, it transmits quickly and cleanly.
But ferric chloride has a terrible drawback - it just gets dirty. If it gets on clothing or any porous surface like wood or paper, it will be a stain for life. So put your Dolce Habana sweatshirts or Gucci felt boots in the safe and wrap them with three rolls of tape. Ferric chloride also destroys almost all metals in the most cruel way. Aluminum and copper are especially fast. So the utensils for etching should be glass or plastic.
I'm throwing 250 gram packet of ferric chloride per liter of water. And with the resulting solution I etch dozens of boards until the etch stops.
The powder must be poured into water. And make sure that the water does not overheat, otherwise the reaction will lead to the release of large quantity heat.
When all the powder has dissolved and the solution has acquired a uniform color, you can throw the board in there. It is desirable that the board floats on the surface, copper side down. Then the sediment will fall to the bottom of the container without interfering with the etching of the deeper layers of copper.
To prevent the board from sinking, you can stick a piece of foam plastic to it with double-sided tape. That's exactly what I did. It turned out very convenient. I screwed in the screw for convenience, so that I could hold it like a handle.
It is better to dip the board into the solution several times, and lower it not flat, but at an angle, so that no air bubbles remain on the surface of the copper, otherwise there will be jambs. Periodically you need to remove it from the solution and monitor the process. On average, etching a board takes from ten minutes to an hour. It all depends on the temperature, strength and freshness of the solution.
The etching process accelerates very sharply if you lower the hose from the aquarium compressor under the board and release bubbles. The bubbles mix the solution and gently knock out the reacted copper from the board. You can also shake the board or container, the main thing is not to spill it, otherwise you won’t be able to wash it off later.
When all the copper has been removed, carefully remove the board and rinse it under running water. Then we look at the clearing so that there is no snot or loose grass anywhere. If there is snot, then throw it into the solution for another ten minutes. If the tracks are etched or breaks occur, it means the toner is crooked and these places will need to be soldered with copper wire.
If everything is fine, then you can wash off the toner. For this we need acetone - the true friend of a substance abuser. Although now it is becoming more difficult to buy acetone, because... Some idiot from the state drug control agency decided that acetone is a substance used to prepare narcotics, and therefore its free sale should be prohibited. It works fine instead of acetone 646 solvent.
Take a piece of bandage and thoroughly moisten it with acetone and begin to wash off the toner. There is no need to press hard, the main thing is not to mess around too quickly so that the solvent has time to be absorbed into the pores of the toner, corroding it from the inside. It takes about two to three minutes to wash off the toner. During this time, even the green dogs under the ceiling will not have time to appear, but it still won’t hurt to open the window.
The cleaned board can be drilled. For these purposes, I have been using a motor from a tape recorder, powered by 12 volts, for many years. It’s a monster machine, although its lifespan lasts for about 2000 holes, after which the brushes burn out completely. You also need to rip out the stabilization circuit from it by soldering the wires directly to the brushes.
When drilling, you should try to keep the drill strictly perpendicular. Otherwise, then you’ll put a microcircuit in there. And with double-sided boards, this principle becomes basic.
The manufacture of a double-sided board occurs in the same way, only here three reference holes are made, as far as possible smaller diameter. And after etching one side (at this time the other is sealed with tape so that it does not get etched), the second side is aligned along these holes and rolled. The first one is sealed tightly with tape and the second one is etched.
On the front side you can use the same LUT method to apply the designation of radio components for beauty and ease of installation. However, I don’t bother that much, but comrade Woodocat from the LJ community ru_radio_electr He always does this, for which I have great respect!
Soon I will probably also publish an article on photoresist. The method is more complicated, but at the same time it gives me more fun to do - I like to play tricks with reagents. Although I still make 90% of the boards using LUT.
By the way, about the accuracy and quality of boards made using the laser ironing method. Controller P89LPC936 in the case TSSOP28. The distance between the tracks is 0.3mm, the width of the tracks is 0.3mm.
Resistors on the top size board 1206 . What's it like?
Terms on specific example. For example, you need to make two boards. One is an adapter from one type of case to another. The second is replacing a large microcircuit with a BGA package with two smaller ones, with TO-252 packages, with three resistors. Board sizes: 10x10 and 15x15 mm. There are 2 options for manufacturing printed circuit boards: using photoresist and the " laser iron". Let's use the "laser iron" method.
The process of making printed circuit boards at home
1. Preparing a printed circuit board design. I use the DipTrace program: convenient, fast, high quality. Developed by our compatriots. Very convenient and pleasant user interface, unlike the generally accepted PCAD. There is a conversion to PCAD PCB format. Although many domestic companies have already begun to accept DipTrace format.
In DipTrace you have the opportunity to see your future creation in volume, which is very convenient and visual. This is what I should get (the boards are shown in different scales):
2. First, we mark the PCB and cut out a blank for the printed circuit boards.
3. We display our project in a mirror image in the highest possible quality, without skimping on toner. After much experimentation, the paper chosen for this was thick matte photo paper for printers.
4. Don’t forget to clean and degrease the board blank. If you don’t have a degreaser, you can go over the copper of the fiberglass with an eraser. Next, using an ordinary iron, we “weld” the toner from the paper to the future printed circuit board. I hold it for 3-4 minutes under slight pressure until the paper turns slightly yellow. I set the heat to maximum. I put another sheet of paper on top for more uniform heating, otherwise the image may “float”. Important point here - uniformity of heating and pressure.
5. After this, after allowing the board to cool a little, we place the workpiece with the paper stuck to it in water, preferably hot. Photo paper quickly gets wet, and after a minute or two you can carefully remove the top layer.
In places where large cluster our future conductive paths, the paper sticks to the board especially strongly. We're not touching it yet.
6. Let the board soak for a couple more minutes. Carefully remove the remaining paper using an eraser or rubbing with your finger.
7. Take out the workpiece. Dry it. If somewhere the tracks are not very clear, you can make them brighter with a thin CD marker. Although it is better to ensure that all tracks come out equally clear and bright. This depends on 1) the uniformity and sufficient heating of the workpiece with the iron, 2) accuracy when removing the paper, 3) the quality of the PCB surface and 4) successful selection of paper. You can experiment with the last point to find the most suitable option.
8. Place the resulting workpiece with future conductor tracks printed on it in a ferric chloride solution. We poison for 1.5 or 2 hours. While we wait, we will cover our “bath” with a lid: the fumes are quite caustic and toxic.
9. We take the finished boards out of the solution, wash and dry. Toner from a laser printer can be easily washed off the board using acetone. As you can see, even the thinnest conductors with a width of 0.2 mm came out quite well. There is very little left.
10. We tin printed circuit boards made using the “laser iron” method. We wash off the remaining flux with gasoline or alcohol.
11. All that remains is to cut out our boards and mount the radio elements!
conclusions
With some skill, the “laser iron” method is suitable for making simple printed circuit boards at home. Short conductors from 0.2 mm and wider are quite clearly obtained. Thicker conductors turn out quite well. Time for preparation, experiments with selecting the type of paper and iron temperature, etching and tinning takes approximately 3-5 hours. But it's much faster than ordering boards from a company. Cash costs are also minimal. In general, for simple budget amateur radio projects, the method is recommended for use.