Creating a printed circuit board using a laser iron. PCB Etching Methods (3 Recipes) PCB Etching Solution

Hello dear friends! At 5:30 in the morning, I specifically woke up early today to write something useful. And yes, today is May 9 on the calendar, so I congratulate you on this great day, Victory Day!

And Today we will talk about a solution for etching printed circuit boards, which is striking in its availability and simplicity. Yes, today we’ll talk about how you can pickle a board with hydrogen peroxide and citric acid, and a little bit of salt.

What pickling solutions exist

For etching printed circuit boards, there are many different solutions, among which there are popular etching mixtures and there are not very popular ones.

In my opinion, the most popular pickling solution in the amateur radio environment is ferric chloride. Why this is so, I do not know, maybe it's a conspiracy of radio shop sellers who specifically offer ferric chloride and tactfully keep silent about alternatives. And there are alternatives:

1. Etching with copper sulphate and salt
2. Etching with ammonium persulfate
3. Etching with sodium persulfate
4. Etching with hydrogen peroxide and hydrochloric acid
5. Etching with hydrogen peroxide and citric acid

If you have more options for etching solutions, I would be grateful if you share them in the comments on this post.

What are the disadvantages of etching in ferric chloride

A solution of ferric chloride is good for everyone, it is not difficult to prepare and the etching process usually goes quickly. When cooking, it is very easy to deal with the concentration, which is called “by eye”. Once prepared solution is enough for dozens of boards. But it has some disadvantages that are very disturbing:

1. The solution is not transparent, which makes it difficult to control the process. You have to constantly remove the board from the pickling solution.
2. A solution of ferric chloride is very dirty plumbing. Each board etching session ends with the process of shuffling plumbing (sinks, bathtubs and everything that the solution can come into contact with).
3. It stains clothes very badly. When working with ferric chloride, you should wear clothes that you will not be sorry to throw away, because the solution is very strongly eaten into the fabric, so much that it is almost impossible to wash it off later.
4. The solution aggressively affects any metal in the vicinity, even if stored in a leaky container, nearby metal objects may become rusty. Somehow I closed a jar of ferric chloride with a metal lid (the lid was painted), after a couple of months this lid turned into dust.

How to Etch Boards in Hydrogen Peroxide and Citric Acid

Although I have always been a supporter of the conservative path, despite all the advantages of the FeCl3 solution, its disadvantages are gradually pushing me to search for alternative pickling mixtures. And so I decided to test the method of etching circuit boards in hydrogen peroxide and citric acid.

On the way home, I went to the grocery store and, in addition to products for a delicious dinner, grabbed 4 sachets of citric acid, 10g each. every. Each bag cost me less than 6r.

I went to the pharmacy and bought a bottle of hydrogen peroxide, it cost me 10 rubles.

I don’t have any project at the moment, so I decided to test the method purely, to understand what the whole point is. I found a piece of foil textolite in my stash and made a few strokes with a permanent marker. This is a kind of imitation of tracks and copper polygons, for experimental work it will do just fine.

The solution is not difficult to prepare, but it is important to observe the proportions. Therefore, pour 100 ml of peroxide into a plastic tray and pour 30 g of citric acid. Since I had 10 g bags, I poured out 3 bags. It remains to salt the whole thing, put 5 g of table salt, this is about 1 teaspoon without a slide.

I noticed that even more salt can be added than is required, this leads to an acceleration of the process. Mix thoroughly. It is very important that you do not need to add water to the solution, so for preparation we choose such a container so that the solution covers the board, or we increase the amount of the solution, observing the proportions.

We put our "printed circuit board" in the resulting solution and observe the process. I want to note that the solution turned out to be completely transparent.

During the etching process, bubbles begin to form and the temperature of the solution increases slightly. Gradually, the solution begins to turn greenish - a sure sign that the etching is in full swing. In general, the whole etching process took me less than 15 minutes, which I was very pleased with.

But when I decided to pickle another board in the same solution, a little larger than this one, then everything turned out to be not so positive. The board was etched exactly by half and the process slowed down very much, slowed down so much that it was necessary to complete the process in ferric chloride.

Apparently the power of the solution is enough for the time while the chemical reaction between hydrogen peroxide and citric acid is going on. The process can be extended by adding and adding the required components.

Benefits of etching in hydrogen peroxide and citric acid

From the experience gained, we can conclude that this method, like others, has its pros and cons, it has both its advantages and disadvantages.

Main advantages:

1. Ease of Access - All components are readily available at your nearest pharmacy and grocery store.
2. Relative cheapness - all components for preparing the solution are not expensive, less than 100 rubles. (at the time of writing)
3. Clear Solution - The resulting solution is clear, making it easier to observe and control the etching process.
4. Etching occurs quite quickly and does not require heating
5. Doesn't stain plumbing

What are the cons

Unfortunately, in addition to all the advantages, this etching method is not without its drawbacks.

Cons of etching in hydrogen peroxide and citric acid:

1. Disposable solution - solution suitable only for single use, i.e. during a chemical reaction taking place in it. It will not be possible to pickle a lot of boards in it, for each time you will have to prepare the solution again.
2. Expensive - despite the fact that all the ingredients are cheap, in the long run the solution is more expensive than the same chlorine gel. After all, for each new board, the solution will have to be prepared anew.

That's basically all the shortcomings. In my opinion, this method of board etching has the right to life and it will definitely find its supporters and admirers. And in some cases, this method may be the only possible alternative, for example, in a remote village with a pharmacy and a grocery store.

And on this I will round off. It's already dawn outside the window and it's time to cook a delicious breakfast.

I once again congratulate you on Victory Day and wish you good luck, success and a peaceful sky over your head!

N/A Vladimir Vasiliev

How to prepare a board made in Eagle for production

Preparation for production consists of 2 stages: technology restrictions check (DRC) and generation of files in Gerber format

DRC

Every PCB manufacturer has technology restrictions on minimum trace widths, trace spacing, hole diameters, and so on. If the board does not meet these restrictions, the manufacturer refuses to accept the board for production.

When creating a PCB file, the default technology limits are set from the default.dru file in the dru directory. As a rule, these limits do not correspond to the limits of real manufacturers, so they need to be changed. You can set the limits just before generating the Gerber files, but it's better to do it right after the board file is generated. To set restrictions, press the DRC button

gaps

Go to the Clearance tab, where the gaps between the conductors are set. We see 2 sections: different signals And Same signals. different signals- defines gaps between elements belonging to different signals. Same signals- defines gaps between elements belonging to the same signal. When moving between input fields, the picture changes, showing the meaning of the input value. Dimensions can be specified in millimeters (mm) or thousandths of an inch (mil, 0.0254 mm).

Distances

The Distance tab defines the minimum distances between the copper and the edge of the board ( Copper/Dimension) and between the edges of the holes ( Drill/Hole)

Minimum dimensions

On the Sizes tab for double-sided boards, 2 parameters make sense: Minimum Width- minimum conductor width and Minimum Drill is the minimum hole diameter.

Belts

The Restring tab defines the sizes of the bands around the vias and pads of the output components. The width of the collar is set as a percentage of the hole diameter, while you can set a limit on the minimum and maximum width. For double-sided boards, the parameters make sense Pads/Top, pads/bottom(pads on the top and bottom layers) and Via/Outer(through holes).

masks

On the Masks tab, the gaps from the edge of the pad to the solder mask are set ( Stop) and solder paste ( Cream). Clearances are specified as a percentage of the smaller pad size, and you can set a limit on the minimum and maximum clearance. If the board manufacturer does not specify special requirements, you can leave the default values ​​​​on this tab.

Parameter limit defines the minimum via diameter that will not be covered by the mask. For example, if you specify 0.6mm, then vias with a diameter of 0.6mm or less will be masked.

Running a check

After setting the restrictions, go to the tab File. You can save the settings to a file by clicking the button. Save as.... In the future, for other boards, you can quickly load the settings ( Load...).

Push button apply the set technology limits apply to the PCB file. It affects layers tStop, bStop, tCream, bCream. Also, vias and pads on output components will be resized to fit the constraints set on the tab. Restring.

Button press Check starts the constraint control process. If the board satisfies all restrictions, the program status line will display the message No errors. If the board does not pass control, a window appears DRC Errors

The window contains a list of DRC errors, indicating the error type and layer. By double-clicking on a line, the area of ​​the board with the error will be shown in the center of the main window. Error types:

too little clearance

hole diameter too small

intersection of tracks with different signals

foil too close to board edge

After correcting the errors, you need to start the control again, and repeat this procedure until all errors are eliminated. The board is now ready to be output to Gerber files.

Gerber file generation

From the menu File select CAM Processor. A window will appear CAM Processor.

The set of file generation parameters is called a task. The task consists of several sections. The section defines output parameters for a single file. Eagle comes with the gerb274x.cam task by default, but it has 2 drawbacks. Firstly, the lower layers are displayed in a mirror image, and secondly, the drill file is not output (one more task will have to be performed to generate the drill). Therefore, consider creating a task from scratch.

We need to create 7 files: board borders, copper top and bottom, silkscreen top, solder mask top and bottom, and drill.

Let's start with the borders of the board. In field Section enter the name of the section. Checking what's in the group style installed only pos. Coord, Optimize And Fill pads. From the list device choose GERBER_RS274X. In the input field File enter the name of the output file. It is convenient to place the files in a separate directory, so in this field we will enter %P/gerber/%N.Edge.grb . This means the directory where the board source file is located, the subdirectory gerber, the original board file name (without extension .brd) with added at the end .edge.grb. Please note that subdirectories are not created automatically, so you will need to create a subdirectory before generating files gerber in the project directory. In the fields offset enter 0. In the list of layers, select only the layer Dimension. This completes the creation of the section.

To create a new section, press Add. A new tab appears in the window. Set the section parameters as described above, repeat the process for all sections. Of course, each section must have its own set of layers:

copper top - Top, Pads, Vias

copper bottom - Bottom, Pads, Vias

silkscreen on top - tPlace, tDocu, tNames

top mask - tStop

bottom mask - bStop

drilling - Drill, Holes

and the filename, for example:

top copper - %P/gerber/%N.TopCopper.grb

bottom copper - %P/gerber/%N.BottomCopper.grb

top silkscreen - %P/gerber/%N.TopSilk.grb

top mask - %P/gerber/%N.TopMask.grb

bottom mask - %P/gerber/%N.BottomMask.grb

drilling - %P/gerber/%N.Drill.xln

For a drill file, the output device ( device) should be EXCELLON, but not GERBER_RS274X

Keep in mind that some board manufacturers only accept files with names in the 8.3 format, that is, no more than 8 characters in the file name, no more than 3 characters in the extension. This should be taken into account when naming files.

We get the following:

Then open the board file ( File => Open => Board). Make sure the board file has been saved! Click Process Job- and we get a set of files that can be sent to the board manufacturer. Please note that in addition to the actual Gerber files, information files will also be generated (with extensions .gpi or .dri) - they do not need to be sent.

You can also display files only from individual sections by selecting the desired tab and pressing Process Section.

Before sending the files to the board manufacturer, it's a good idea to preview the output with a Gerber viewer. For example, ViewMate for Windows or for Linux. It can also be useful to save the board in PDF (in the board editor File->Print->PDF button) and upload this file to the manufacturer along with the gerberas. And then they are also people, this will help them not to make a mistake.

Technological operations that must be performed when working with photoresist SPF-VShch

1. Surface preparation.
a) cleaning with polished powder ("Marshalit"), size M-40, washing with water
b) decapitation with 10% sulfuric acid solution (10-20 sec), washing with water
c) drying at T=80-90 gr.C.
d) check - if within 30 seconds. a continuous film remains on the surface - the substrate is ready for use,
if not, repeat all over again.

2. Deposition of photoresist.
The photoresist is applied on a laminator with Tshafts = 80 gr.C. (See laminator operating instructions).
For this purpose, the hot substrate (after the drying cabinet) simultaneously with the film from the SPF roll is directed into the gap between the rolls, and the polyethylene (matt) film should be directed towards the copper side of the surface. After pressing the film to the substrate, the movement of the rollers begins, while the polyethylene film is removed, and the photoresist layer is rolled onto the substrate. Mylar protective film remains on top. After that, the SPF film is cut on all sides to fit the substrate and kept at room temperature for 30 minutes. Exposure is allowed for 30 minutes to 2 days in the dark at room temperature.

3. Exposure.
Exposure through a photomask is carried out on SKCI or I-1 installations with UV lamps of the DRKT-3000 or LUF-30 type with a vacuum of 0.7-0.9 kg/cm2. The exposure time (to obtain a picture) is regulated by the installation itself and is selected experimentally. The template must be well pressed against the substrate! After exposure, the workpiece is aged for 30 minutes (up to 2 hours is allowed).

4. Manifestation.
After exposure, the process of developing the picture is carried out. For this purpose, the upper protective layer, the lavsan film, is removed from the surface of the substrate. After that, the workpiece is lowered into a solution of soda ash (2%) at T=35 gr.C. After 10 seconds, the process of removing the unexposed part of the photoresist using a foam swab begins. The time of manifestation is selected empirically.
Then the substrate is removed from the developer, washed with water, decapitated (10 sec.) with a 10% solution of H2SO4 (sulfuric acid), again with water and dried in an oven at T=60°C.
The resulting drawing should not flake off.

5. The resulting drawing.
The resulting pattern (photoresist layer) is resistant to etching in:
- ferric chloride
- hydrochloric acid
- copper sulphate
- aqua regia (after additional tanning)
and other solutions

6. Shelf life of photoresist SPF-VShch.
Shelf life of SPF-VShch is 12 months. Storage is carried out in a dark place at a temperature of 5 to 25 gr. C. in an upright position, wrapped in black paper.

Hello! In this article I will talk about the easiest and cheapest way to pickle boards at home. For this we need:

1. Hydrogen peroxide 100 ml 3%
2. Citric acid 30 g
3. Salt 3 g

As you can see, all components are available to everyone. We buy hydrogen peroxide at the pharmacy, citric acid and salt at the grocery store. Everything will be quite cheap - no more than 100 rubles.

Citric acid and hydrogen peroxide

Now let's start preparing the solution. To do this, you need to find some plastic container by the size of the fee. I used a regular plastic tray.

Plastic trays

Pour hydrogen peroxide into the tray, then pour in citric acid and salt. We mix everything. We can assume that the solution is ready. Before lowering the board into the solution, you need to check if everything is fine with it. Namely, how the tracks are plotted. To do this, we take the template that was applied to the board and the board itself and compare the drawing. If there are places where the tracks break off, you need to take a marker or varnish and finish them. The main thing is that the marker is indelible. This can be checked like this: it should have the inscription: permanent marker. I advise you to pay special attention to this, because if it is an ordinary marker, nothing will come of it.

Marker for drawing tracks

Board drawn with a marker

After inspecting the board, lower it into the liquid. Nothing will happen right away so that the board is quickly etched, you need to heat the solution. To do this, take a pot of water and carefully lower the tray in it so that water does not get into it. And put it all on the stove. When the solution is heated (50 degrees), the reaction will start, this can be seen by the release of bubbles.

PCB etching

The etching process itself takes about 15-20 minutes, and if not heated, it can take more than an hour. When you see that all the tracks are etched, carefully take out the board and wash it under the tap. Pour out the solution, as it will no longer work.

Tinning and drilling boards

As a result, we get a rather good printed circuit board, the board did not quite turn out in the photo due to the fact that the template was poorly applied. If you do everything right, you will do better.

Assembly of parts on the board

Finished device with this board (guess what it is)

As you can see, this is the cheapest and affordable way board etching. The only disadvantage is that the solution is disposable, that is, each time you need to make a new solution. Good luck to all. Kirill.

Discuss the article SIMPLE AND CHEAP WAY PCB ETCHING

Recently discovered on the Internet new method etching of printed circuit boards, which differs from the classical etching methods, in addition, this method does not have the characteristics of traditional ferric chloride And ammonium persulfate shortcomings. Ferric chloride, with its non-washable stains on clothes and, as a result, with damaged things, may not have suited many for a long time. Also ammonium persulfate, not everyone has a separate pickling table at home - soldering, most likely most poison, like me, in the bathroom. Sometimes, as a result of careless actions with ammonium persulfate and drops on clothes, small holes form over time, things become damaged.

Some may say that persulfate suits me because of its etching speed, and so, the new etching method allows you to etch boards, I think with no less speed. Yesterday I etched the fee for half an hour, the drawing was drawn on hastily marker, the narrowest paths were 1 mm wide, no undergrass was noticed. The photo of the board is below, though after I tinned and soldered all the details to the board, just to show that even narrow paths are obtained without undercuts, I think this is enough. But I want to note right away that the drawing transferred to the printed circuit board by the method LUT (laser ironing technology) is preserved better, people, according to reviews, when etching with this method, even narrow tracks 1 mm wide are consistently good.

Now let's get down to business. On a board with dimensions of 35 * 25, which I poisoned, I spent the following ingredients: bottle of pharmacy hydrogen peroxide 50 ml, worth 3 rubles and 1 sachet 10 grams food grade citric acid, costing 3.5 rubles, salt teaspoon(used as a catalyst) of course for free, any one you have in your kitchen will do, even iodized. The exact proportions are not required here, we make something like this solution: pour hydrogen peroxide so that the board is hidden by 5 mm, add 10 grams (in my case, a bag) of citric acid and put a teaspoon of salt .

It is not necessary to add water, the liquid is used the one that is in the peroxide. If you plan to etch a large board, 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 blue. During etching, we move the board in containers, because gas bubbles will accumulate on the board, preventing etching.

Toward the end of etching, we remove the board from the solution with tweezers and inspect it. If we draw a drawing with a marker, then 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 solution remaining from etching can be poured into the sewer, skipping after a large number of water. Keep the solution for reuse, I think no one will, it is always easier to make a new solution if necessary than to wait longer when pickling with the old solution.

Saving time and money in comparison with the old methods, I think it is obvious to everyone. You can also use concentrated peroxide sold in hairdressing stores or hydroperite tablets, but here the ratio of ingredients will have to be selected by everyone himself, since he did not experiment with them. I post, as promised, a photo of the board etched by this method, I made the board in a hurry.

A little more about this useful thing, how vertical baths. If uniform and high-quality bilateral etching is required, vertical baths with solution mixing are convenient. Mixing is done by introducing a tube from an aquarium aerator into the bath. Also, the vertical bath has a minimum evaporation area. In addition, there will be no sticky dirt if the mortar is old and littered. I wish you successful pickling without undercuts. was with you AKV .

Discuss the article PCB ETCHING

In the article we will talk about the methods of manufacturing a printed circuit board and etching the board.

There are many ways to make a printed circuit board. The main method that I personally use is the manufacture of a board from foil textolite (getinaks), by applying a drawing with a drawing pen and etching in a chemical solution. It so happened that I started drawing circuit boards from the sixth grade of the school (today - from the fifth), when computers were the size of entire rooms. At that time, I "drifted". Therefore, I draw a board on a sheet of paper in a cage faster than on a computer, using special programs. True, the most voluminous board in terms of element base that I have ever drawn by hand was a board consisting of fourteen microcircuits and a couple of hundred simple elements.

Making a board by drawing a drawing with a drawer or, more often, in Lately, LUT (laser-ironing technology) and etching in a chemical solution consists of the following steps, the difference from other methods may vary slightly in the operations themselves and in their sequence:

1. Layout of the placement of radio elements on the board and routing of conductors (tracks). Currently, there are many programs for the development of radio boards. It's easier to just use them. It is possible to engage in development without the use of special programs, but this requires some perseverance and many times more time. In this case, for convenience, the board is drawn on a sheet of paper in a cage, and for redevelopment it is drawn again;

2. A board of the required dimensions is cut out of foil textolite, or getinaks. More comfortable material is a textolite, it is essentially a multilayer fiberglass, and the foil keeps better on it than on getinaks. Getinax is a sheet material made of pressed paper impregnated with bakelite varnish. Getinaks is a lower quality material than textolite, and has several properties that I personally do not like:

- can flake;

- printed conductors bounce off overheating faster than textolite, which makes it difficult to replace radio components without damaging the board if they fail;

- there are cases of overheating of radio components, from which the radio board can “smoke”. The same happens when moisture enters high-voltage circuits. Burnt getinax often turns into a conductor (something like graphite). The same happens with getinax if moisture accidentally enters high-voltage circuits. The latter can bring you a lot of trouble;

But with all this, it is decently cheaper and cut with scissors. This is useful when you need to make a quick one-sided board on SMD parts.

3. The ends of the board are processed from sharp corners and burrs with a file or sandpaper;

4. The cut board is wrapped in a sheet with a drawn board. With a thin core, with light blows of a hammer, pits (marking) of future holes are made in those places that were previously marked on the sheet;

5. In the marked places, holes are drilled for future radio components. For small parts - resistors, capacitors, thin-terminal transistors, a 0.5 mm drill is used, for thicker leads, a 0.7 mm drill is used. Other sizes can be used if needed. As a drill, it is more convenient to use a portable drilling machine, which can be purchased at a specialized radio store. You can also use a hand-held electric drill with some skill;

6. After drilling the holes, the board is processed with sandpaper. All burrs resulting from drilling are cleaned off, and the foil is cleaned for further drawing tracks and etching;

7. A drawing pen is made from an ordinary empty rod from a ballpoint pen. To do this, the rod is heated over the flame of a match (or lighter), and when the plastic melts, the rod is pulled out. After the plastic hardens, the end of the drawing pen is cut off to obtain a hole with a diameter of approximately 0.2 ... 0.4 mm;

8. Lacquer (more conveniently - nail polish) 2 ... 5 cm in height is typed into the drawing pen, after which a printed circuit board is drawn: soldering pads are made around the holes, and printed circuit paths are drawn between these pads. With some skill and using rulers as guides, the quality of the picture may not be inferior to factory radio boards;

9. After the varnish dries, the parts of the board not covered with varnish are etched by placing the board in a solution of ferric chloride. At the same time, the copper of the tracks protected by varnish is not etched, and the copper coating of the board not covered with varnish, entering into chemical reaction dissolves in ferric chloride. To speed up the etching process, the solution with the board can be heated in a water bath, or simply placed on a central heating battery;

10. After etching, the board is washed with water and using a cotton swab moistened with acetone or another solvent, the varnish is removed from the board, after which it is washed again under running water;

11. Soldering radio components is best done using low-melting solder and flux - rosin dissolved in alcohol.

Should be added:

As a drawing pen, you can use a disposable syringe, while breaking the oblique cut of the needle, grind it so that there are no sharp scratching surfaces of the tip. Recently, there are many markers on sale, the dye of which is not washed off with water and gives a sufficiently strong protective layer, so they can also be used as a drawing pen.

Some masters, after etching the board, are also tinkering. Tinning is done in one of two ways:

1. Soldering iron;

2. The iron bath is filled with Rose or Wood alloy. The alloy, in order to avoid solder oxidation, is completely covered with a layer of glycerin on top. For tinning, the board is immersed in the melt for no more than five seconds. The bath is heated with an electric stove.

Recently, the printer method of transferring a radio card pattern has become more and more widespread.

It consists in the following:

1. With the help of special programs, a radio board is designed and drawn;

2. The image of the board in mirror image is printed on a laser printer on a substrate. In this case, thin coated paper (covers from various magazines), fax paper, or film for laser printers is used as a substrate.

3. A substrate is applied to the prepared board with the front side (picture) and, with the help of a very hot iron, is “lapped” to the board. To evenly distribute the pressure of the iron on the substrate, it is recommended to lay several layers of thick paper between them. The toner melts and sticks to the board.

4. After cooling, two options for removing the substrate are possible: either the substrate is simply removed after transferring the toner to the board (in the case of film for laser printers), or it is pre-soaked in water and then gradually separated (coated paper). At the same time, the toner remains on the board. After removing the substrate, in those places where the toner still separated, you can retouch the board manually.

5. The board is etched in a chemical solution. During etching, the toner does not dissolve in ferric chloride.

This method allows you to get a very beautiful printed circuit, but you need to get used to it, because it may not work out the first time. The fact is that a certain high-temperature regime is necessary. There is only one criterion here: the toner must have time to melt enough to stick to the surface of the board, and at the same time it must not have time to reach a semi-liquid state so that the edges of the tracks do not flatten out. Removing the paper sheet requires some softening with water, otherwise the paper sheet may come off with the toner. Drilling of holes in the printed circuit board is carried out after etching.

PCB etching

There are many compositions for chemically etching copper from a printed circuit board. All of them differ in the speed of the reaction and the availability of chemical reagents necessary for the preparation of the solution. Do not forget that any chemistry is harmful to health, so do not forget about precautions. Here are the chemical solutions for etching printed circuit boards that I personally used:

1. Nitric acid (HNO 3)- the most dangerous and not popular reagent. Transparent, has a pungent odor, is highly hygroscopic, and evaporates just as strongly. Therefore, it is not recommended for storage at home. Not used for etching pure form, and a solution with water in a ratio of 1/3 (one part acid to three parts water). Do not forget that water does not pour into acid, but vice versa - acid into water. The etching process takes no more than five minutes, with active gas evolution. "Nitrogen" dissolves the varnish, so before using it, you need to let the varnish dry well. Then, during etching, he will not have time to soften and fall behind copper plating. Precautions must be strictly followed.

2. A solution of sulfuric acid (H 2 SO 4) and hydrogen peroxide (H 2 O 2). To prepare this solution, it is necessary to throw four tablets of hydrogen peroxide into a glass of ordinary battery electrolyte (a solution of sulfuric acid in water) (the pharmacy name is Hydroperit). The finished solution should be stored in a dark container that is not hermetically sealed, since gas is released during the decomposition of hydrogen peroxide. The PCB etch time is on the order of one hour for a well stirred fresh solution at room temperature. This solution after etching can be restored by adding hydrogen peroxide H 2 O 2 . The assessment of the required amount of hydrogen peroxide is carried out visually: the copper board immersed in the solution must be repainted from red to dark brown color. The formation of bubbles in the solution indicates an excess of hydrogen peroxide, which slows down the etching reaction. Precautions must be strictly followed.

Attention: When using the two previously mentioned solutions, all precautions must be taken when working with caustic chemicals. All work must be carried out only on fresh air or under the hood. If the solution comes into contact with the skin, it must be washed immediately big amount water.

3. Ferric chloride (FeCl 3)- the most popular reagent for etching printed circuit boards. Dissolve 150 g of ferric chloride powder in 200 ml of warm water. The etching process in this solution can take from 15 to 60 minutes. The time depends on the freshness of the solution and the temperature. After etching, the board must be washed with plenty of water, preferably with soap (to neutralize acid residues). The disadvantages of this solution include the formation of waste during the reaction, which settle on the board and prevent the normal course of the etching process, as well as a relatively low reaction rate.

4. Salt solution (NaCl) and blue vitriol(CuSO 4) in water. In 500 ml hot water(about 80 ° C) dissolve four tablespoons of table salt and two tablespoons of copper sulfate crushed into powder. The solution is ready for use immediately after cooling (when using heat-resistant paint, cooling is not necessary). The etching time is about 8 hours. To speed up the etching process, the solution with the board can be heated up to 50 °C.

5. A solution of citric acid in hydrogen peroxide (H 2 O 2). In a small bath (up to 100 ml), the printed circuit board is poured with a large volume of hydrogen peroxide, after which 1 tablespoon of citric acid is added there. After that, the process of etching the printed circuit board begins. It is actively accompanied by a change in the color of the liquid from transparent to blue. The edges turn out to be even and, if you first walk along the foil-coated fiberglass with fine emery, then everything will be etched very evenly.

Using this method, I managed to get boards with the following parameters:

The gap between the conductors is 0.2 mm.

With a set conductor thickness of 0.25 mm, in fact, it turned out to be 0.2-0.22 mm.

Board dimensions up to 100x200 mm.

If you need to pickle faster, you can add a pinch of regular table salt. It will speed up the process, but be careful: During the pickling process, thermal energy is released and usually the solution warms up quite a bit. For my long-term practice of working with this solution, it exploded 2 times and “smeared” everything around. Of course, everything faded very quickly. with an ordinary rag with soda and no traces on clothes or things from it (unlike ferric chloride, it does not remain), but it is quite interesting to observe this.

The average pickling time is 20-30 minutes.

I did not use other solutions for etching printed circuit boards. It is most pleasant to work with the last item, since the components can be obtained in any city.

If you need quality

In principle, a printed circuit board can also be ordered at a plant specialized for their production. Of course, it costs more than you would make it yourself, but the workmanship will be many times better. If you have a lot of such prototypes, then I highly recommend watching a video on the production of printed circuit board assembly right away.

The point here is the following. The factory takes money for 2 things: for pre-production, during which it transfers your files from printed circuit board to its standard and manufactures equipment, and for the manufacture itself. The production itself is not an expensive thing: factories buy blanks for radio boards in large volumes and the production itself is cheaper from them, but they charge an average of 2-3 thousand rubles for preparation. For me, paying that kind of money for the manufacture of one board does not make sense. But, if there are 10-20 of these boards, then this money for preparation is divided among all the boards and it turns out cheaper.