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How to make printed circuit boards. Making a printed circuit board with your own hands

Greetings dear friends! Today I want to tell you one wonderful news and this news may be of interest to you, so be sure to read to the end.

Friends walking through the pages of my blog, you probably know that I periodically post various amateur radio designs that I myself make. So, in the manufacture of printed circuit boards, I have achieved stability, when a completely high-quality result is obtained literally from one or the second attempt. And those who have come across amateur radio technology LUT, I think they will agree with me that this result is not even bad.

In where I described all the intricacies of manufacturing printed circuit boards at home, everyone will find all the comprehensive information on this issue. However, for a number of reasons, not everyone who wants to get a printed circuit board has a desire to master this tricky technology.

Therefore, for everyone who wants to get a high-quality printed circuit board and at the same time does not want to bother with various technological methods, I have a cool offer!

And this proposal is that I open the production of printed circuit boards to order. What does it mean?

This means that if you need to manufacture printed circuit boards, then just leave your email in the form below.

How will the interaction be carried out?

  1. You leave your email through the specified form
  2. I contact you via email where we discuss the details (PCB file, technical details, production volume, timing, payment and delivery)
  3. If everything suits you, then pay for the order and I will start making boards.
  4. After manufacturing, I photograph the boards and send you a photo, if the result suits you, then I send it to your address.

If the result does not suit you, I am always ready to return the money!

What technology will be used to manufacture printed circuit boards?

Printed circuit boards will be manufactured using the LUT technology or otherwise the “Laser iron” method, while the following actions are performed:

  1. The printed circuit board drawing created by you in some editor (Sprint layout or Eagle CAD or some other) is transferred to photo paper using a laser printer (I have an old samsung ML1615 printer). It is also possible to use a bitmap image as a source file (for example, from a magazine or from the Internet).
  2. Further, the image with the help of an ordinary iron is transferred to a cleaned and fat-free fiberglass.
  3. The board with the printed image is etched in ferric chloride, as a result, everything that is not covered with paint disappears.
  4. Now it remains to drill holes and ALL!

As a result of these actions, a printed circuit board with a conductive pattern comparable to domestic military production is born! And indeed it is!

What PCBs can I manufacture?

  • At the moment, I am fluent in LUT technology and can produce printed circuit boards up to A5 format (148x210).
  • Boards can be both single-sided and double-sided.
  • The minimum thickness of the printed conductor reaches 0.1 mm, but in practice it is not worth doing less than 0.3 mm. It’s not a problem to get such a pattern on the board, only very thin tracks are sensitive to a heated soldering iron ...
  • The minimum diameter of the mounting hole that I can provide reaches 0.5mm.

How is the delivery?

  • At the moment delivery by mail of Russia is possible.

Well, friends, if you have any questions, be sure to ask them through the feedback form, I will definitely answer them!

Vladimir Vasilyev was with you and see you soon!

The practice of design and installation, directly related to electronics, cannot do without the main part - the printed circuit board. The initial development of some electronic device is, of course, permissible with the help of surface mounting. However, a full-fledged printed circuit board will still have to be made if we are talking about a serious electronic device. There are two options: order the manufacture of a printed circuit board in a service or make a printed circuit board with your own hands directly at home. The first option requires a solid financial investment and two to three weeks of waiting. The second requires nothing but personal desire, a piece of foil textolite and a small amount of ferric chloride.

Sheet textolite, on one or both sides with a thin layer of copper, is traditionally used for the manufacture of printed electronic circuit boards.

Usually a rigid base with wiring of electronic circuits for soldering electronic parts is the priorities of a specialized manufacturing area.

However, the design of electronics for personal needs and in small copies looks more rational when the technology for the production of "seals" is available in everyday life.

It is quite possible to obtain such a result of work at home using simple available means, tools, materials

If you master all the subtleties of production and stock up on the necessary material, the manufacture of printed circuit boards at home is not excluded, if not on an industrial scale, then in quantities sufficient for business.

There are several technologies for drawing and etching miniature tracks on foil textolite. Starting from the method of a simple drawing of an electronic circuit with nail polish, followed by chemical etching, and ending with automatic laser wiring and micron cutting.

However, for home conditions, a special technique is required - effective, but at the same time budgetary and relatively uncomplicated.

PCB manufacturing at home

Here - as part of a kind of tutorial, is considered using the technology of transferring toner with a laser printer.

This method has been developed for a long time, but is still accompanied by a lot of new tips and tricks, thanks to which the efficiency only increases.

What does a home electronics engineer need?

  • design program,
  • laser printer,
  • any glossy magazine,
  • household iron,
  • one or two plastic containers,
  • small brush or toothbrush
  • latex gloves,
  • ferric chloride,
  • foil textolite.

Almost all components of the list can be found in the household. The exceptions are: ferric chloride and textolite with foil.


Two materials: iron chloride and foil textolite, which you will need to buy. Everything else is usually available among household items and materials.

These two list items are closed through a visit to an electronics store or radio market. Such outlets are available in any medium-sized settlement. In extreme cases, you can order both components via the Internet.

Meanwhile, ferric chloride is quite replaceable by another chemical substance obtained on the basis of a mixture of copper sulphate (MC) and common table salt (PS). The mixture is made in the ratio of 1 part of MK to 2 parts of PS, diluted in 0.5 liters of boiling water.

Usually, for the manufacture of a medium-sized electronic printed circuit board, it is enough to take 4 tablespoons of MK and 2 tablespoons of PS. Thoroughly stir the powder mixture poured with boiling water and let it stand.

The only difference between such a solution and FeCl 3 is a slightly longer etching time. But on the other hand, a mixture on copper sulphate is safer than FeCl 3. Copper sulfate (powdered) is available at any hardware store.

Creating a PCB design

To create a PCB pattern design, the KiCad computer program seems to be optimal - a professional tool for drawing electronic printed circuit boards, but at the same time free.

The KiCad software provides the user with a brush routing function, making it easy to route differential pairs, interactively adjust the length of the trace.


The working window of the KiCad program, a professional layout tool that is indispensable in the PCB manufacturing process. The software is distributed free of charge

With the schematic editor without limits. There is an extensive library of circuit symbols. Also, the built-in schematic editor allows you to master working with projects without much difficulty.

Everything that is drawn by the program in red belongs to the frontal surface. The yellow lines are the pattern of the reverse side of the printed circuit board.

The created drawing must be exported to pdf format. To do this, "KiCad" has a tool "Plot". Using "Plot", you should select the mirror image.

Printing a wiring pattern on a printer

After receiving the PCB file in pdf format, you need to print the project on a laser printer. To perform this operation, a page of any glossy magazine is suitable.

The page is inserted into a laser printer. Along with magazine, it is permissible to use plain glossy paper. You don't have to worry about pre-existing images on the magazine page. They won't interfere.


Toner print on glossy magazine page. As you can see from the figure, the print quality is quite high. The same mark should be on the printed circuit board foil.

The factor of the presence of third-party images does not have any effect on the process. In any case, the printer toner drawing remains on the glossy surface of the magazine page (paper). And this is exactly the result that you want to get.

It is advisable to print twice (on two different pages) to make sure that the printed pattern does not have spots, smears, or other defects.

Transferring wiring from printer to foil

If the trace of the printed circuit board layout is qualitatively issued by a laser printer, the glossy page of the magazine with the resulting print should be carefully removed from the printer and placed pattern-side down on the copper surface of the textolite.


Heat treatment of a printed circuit board using a conventional household iron. Heating temperature - maximum. Otherwise, the quality of the transfer suffers.

The heated sole of the iron presses a magazine sheet with a printed layout of the circuit to the surface of the foil textolite. Hold the iron on the sheet without moving for about 30 seconds.

Next, you need to smooth the surface of the sheet with an iron in circular motions for 2-3 minutes. During this period of time, by thermal treatment, the toner firmly adheres to the copper coating of the textolite.


The result of transferring a toner print from a magazine page to the copper coating of the textolite. Looks no worse than the industrial version

The completion of the process of transferring the imprint onto the textolite copper foil is the removal of the glued magazine sheet. This requires patience and accuracy.

Textolite from glued paper is a tray with cold water, where you need to place the object to be processed for a while.

Water softens the paper, which ensures complete removal of the remaining paper fibers. At the same time, the toner remains on the textolite.

So, the drawing of the connection diagram is applied to the textolite. You can proceed to the next part of the process - etching excess copper.


Etching of copper in a solution of ferric chloride. The chemical content of ferric chloride is dangerous. Therefore, protective accessories should be used.

This will require a solution of ferric chloride, poured into a plastic bath of suitable size.

Attention! Ferric chloride solution is a hazardous chemical.

Be sure to carry out pickling work inside a well-ventilated area. Protective accessories - rubber gloves and goggles are also required.

It is recommended to equip the printed circuit board with a thread stretched through a hole drilled in a free corner of the workpiece. This accessory will allow you to periodically remove the workpiece from the solution for control. Or you can use plastic tweezers.

The average etching time with ferric chloride is approximately 20-25 minutes. True, the specific time value largely depends on the size of the workpiece and the volume of copper that needs to be etched.

Once the unprinted copper has been etched away, the PCB should be removed from the solution and placed in a bowl of running water.


Thorough washing of the finished product is essential. If excess ferric chloride remains on the surface, there is a risk of damage to the wiring

The remaining solution of ferric chloride should be poured from the bath into a sealed plastic container and tightly closed with a lid. This solution can be used repeatedly.

The etched printed circuit board should be thoroughly washed with water and soap. Next, it remains only to clean the copper tracks of the printed circuit board, preserved intact under the toner layer.

The same fine-grained skin or metal mesh is applicable here. After cleaning, the printed circuit board is cut to the required size, the edges are aligned with a fine rasp. That's all - the electronic printed circuit board is ready.

In this way, it is possible to cook directly at home electronic printed circuit boards of various complexity, including double-sided ones.

It should be noted that the production quality of printed circuit boards is quite decent by the method of "magazine" printing on a laser printer.

Another original technique for manufacturing printed circuit boards

Tahiti! .. Tahiti! ..
We have not been to any Tahiti!
We are well fed here!
© Cartoon cat

Introduction with digression

How were boards made before in domestic and laboratory conditions? There were several ways, for example:

  1. drew future conductors with penguins;
  2. engraved and cut with cutters;
  3. they glued adhesive tape or electrical tape, then the drawing was cut out with a scalpel;
  4. the simplest stencils were made, followed by drawing with an airbrush.

The missing elements were drawn with drawing pen and retouched with a scalpel.

It was a long and laborious process, requiring remarkable artistic abilities and accuracy from the “drawer”. The thickness of the lines hardly fit into 0.8 mm, there was no repetition accuracy, each board had to be drawn separately, which greatly hindered the release of even a very small batch printed circuit boards(further PP).

What do we have today?

Progress does not stand still. The times when radio amateurs painted PP with stone axes on mammoth skins have sunk into oblivion. The appearance on the market of publicly available chemistry for photolithography opens up completely different prospects for the production of PP without metallizing holes at home.

Let's take a quick look at the chemistry used to make PP today.

Photoresist

You can use liquid or film. Film in this article will not be considered due to its scarcity, the difficulties of rolling to the PCB and the lower quality of the printed circuit boards obtained at the output.

After analyzing the market offerings, I settled on POSITIV 20 as the optimal photoresist for home PCB production.

Purpose:
POSITIV 20 photosensitive varnish. It is used in small-scale production of printed circuit boards, engravings on copper, when carrying out work related to the transfer of images to various materials.
Properties:
High exposure characteristics ensure good contrast of transferred images.
Application:
It is used in areas related to the transfer of images to glass, plastics, metals, etc. in small-scale production. The method of application is indicated on the bottle.
Characteristics:
Color: blue
Density: at 20°C 0.87 g/cm3
Drying time: at 70°C 15 min.
Consumption: 15 l/m2
Maximum photosensitivity: 310-440nm

The instructions for the photoresist say that it can be stored at room temperature and it is not subject to aging. Strongly disagree! It should be stored in a cool place, for example, on the bottom shelf of the refrigerator, where the temperature is usually maintained at +2+6°C. But in no case do not allow negative temperatures!

If you use photoresists that are sold "in bulk" and do not have light-tight packaging, you need to take care of protection from light. It is necessary to store in total darkness and temperature +2+6°C.

Enlightener

Similarly, I find TRANSPARENT 21, which I use all the time, to be the most suitable illuminator.

Purpose:
Allows direct transfer of images to surfaces coated with POSITIV 20 photosensitive emulsion or other photoresist.
Properties:
Gives transparency to paper. Provides UV light transmission.
Application:
For quick transfer of contours of drawings and diagrams to the substrate. Allows you to significantly simplify the process of reproduction and reduce time s e costs.
Characteristics:
Color: transparent
Density: at 20°C 0.79 g/cm3
Drying time: at 20°C 30 min.
Note:
Instead of plain paper with an illuminator, you can use a transparent film for inkjet or laser printers depending on what we will print the photomask on.

Photoresist Developer

There are many different solutions for developing photoresist.

It is advised to develop with a solution of "liquid glass". Its chemical composition: Na 2 SiO 3 * 5H 2 O. This substance has a huge number of advantages. The most important thing is that it is very difficult to overexpose the BP in it you can leave the BP for a non-fixed time. The solution almost does not change its properties with temperature changes (there is no risk of decomposition with increasing temperature), it also has a very long shelf life its concentration remains constant for at least a couple of years. The absence of the problem of overexposure in the solution will make it possible to increase its concentration in order to reduce the time of manifestation of PP. It is recommended to mix 1 part concentrate with 180 parts water (a little over 1.7 g of silicate in 200 ml of water), but it is possible to make a more concentrated mixture so that the image develops in about 5 seconds without the risk of surface damage due to overexposure. If it is not possible to purchase sodium silicate, use sodium carbonate (Na 2 CO 3) or potassium carbonate (K 2 CO 3).

I have not tried either the first or the second, so I will tell you what I have been showing without any problems for several years now. I use an aqueous solution of caustic soda. For 1 liter of cold water 7 grams of caustic soda. If there is no NaOH, I use a KOH solution, doubling the concentration of alkali in the solution. Development time 30-60 seconds with correct exposure. If, after 2 minutes, the pattern does not appear (or appears weakly), and the photoresist begins to wash off from the workpiece, it means that the exposure time has not been chosen correctly: you need to increase it. If, on the contrary, it quickly appears, but both the illuminated areas and the unexposed areas are washed off - either the concentration of the solution is too high, or the quality of the photomask is poor (ultraviolet passes freely through the “black”): you need to increase the print density of the template.

Copper pickling solutions

Excess copper from printed circuit boards is etched using various etchants. Among people doing this at home, ammonium persulfate, hydrogen peroxide + hydrochloric acid, copper sulfate solution + table salt are often common.

I always poison with ferric chloride in glassware. When working with the solution, you need to be careful and attentive: if it gets on clothes and objects, rusty spots remain, which are difficult to remove with a weak solution of citric (lemon juice) or oxalic acid.

We heat the concentrated solution of ferric chloride to 50-60 ° C, immerse the workpiece in it, gently and effortlessly drive the glass rod with a cotton swab at the end through areas where copper is worse etched, this achieves more even etching over the entire area of ​​the PCB. If the speed is not forced to equalize, the required duration of etching increases, and this eventually leads to the fact that in areas where copper has already been etched, etching of the tracks begins. As a result, we do not have what we wanted to get. It is highly desirable to provide continuous mixing of the pickling solution.

Chemistry for removing photoresist

What is the easiest way to wash off the already unnecessary photoresist after etching? After repeated trial and error, I settled on ordinary acetone. When it is not there, I wash it off with any solvent for nitro paints.

So, we make a printed circuit board

Where does a high quality PCB start? Right:

Creating a high quality photomask

For its manufacture, you can use almost any modern laser or inkjet printer. Given that we are using a positive photoresist in this article, where copper should remain on the PCB, the printer should draw black. Where there should be no copper the printer should not draw anything. A very important point when printing a photomask: you need to set the maximum dye watering (in the printer driver settings). The more black the shaded areas are, the more likely you are to get a great result. Color is not needed, a black cartridge is enough. From that program (we will not consider programs: everyone is free to choose for himself from PCAD to Paintbrush), in which the photomask was drawn, we print on a regular sheet of paper. The higher the resolution when printing and the better the paper, the higher the quality of the photomask will be. I recommend at least 600 dpi, the paper should not be very thick. When printing, we take into account that the side of the sheet on which the paint is applied, the template will be placed on the PP blank. If done otherwise, the edges of the PCB conductors will be blurry, fuzzy. Let the paint dry if it was an inkjet printer. Next, we impregnate TRANSPARENT 21 paper, let it dry and the photomask is ready.

Instead of paper and an illuminator, it is possible and even very desirable to use a transparent film for laser (when printing on a laser printer) or inkjet (for inkjet printing) printers. Please note that these films have unequal sides: only one working. If you will be using laser printing, I highly recommend doing a "dry" run of the film sheet before printing - just run the sheet through the printer, simulating printing, but not printing anything. Why is this needed? When printing, the fuser (oven) will heat up the sheet, which will inevitably lead to its deformation. As a consequence, there is an error in the PP geometry at the output. In the manufacture of double-sided PP, this is fraught with a mismatch of layers with all the consequences And with the help of a “dry” run, we will warm up the sheet, it will deform and will be ready for printing a template. When printing, the sheet will pass through the oven a second time, but the deformation will be much less significant checked repeatedly.

If the PCB is simple, you can draw it manually in a very convenient program with a Russified interface Sprint Layout 3.0R (~650 KB).

At the preparatory stage, it is very convenient to draw not too bulky electrical circuits in the also Russified sPlan 4.0 program (~ 450 KB).

This is how ready-made photomasks printed on an Epson Stylus Color 740 printer look like:

We print only in black, with the maximum watering of the dye. Material transparent film for inkjet printers.

Preparing the PCB surface for photoresist application

For the production of PP, sheet materials with applied copper foil are used. The most common options are with a copper thickness of 18 and 35 microns. Most often, for the production of PP at home, sheet textolite (a fabric pressed with glue in several layers), fiberglass (the same thing, but epoxy compounds are used as glue) and getinaks (pressed paper with glue) are used. Less often sittal and polycor (high-frequency ceramics are rarely used at home), fluoroplast (organic plastic). The latter is also used for the manufacture of high-frequency devices and, having very good electrical characteristics, can be used anywhere and everywhere, but its high price limits its use.

First of all, you need to make sure that the workpiece does not have deep scratches, burrs and areas affected by corrosion. Next, it is desirable to polish the copper to a mirror. We polish without being particularly zealous, otherwise we will erase the already thin layer of copper (35 microns) or, in any case, we will achieve different thicknesses of copper on the surface of the workpiece. And this, in turn, will lead to a different etching speed: it is etched faster where it is thinner. And a thinner conductor on the board is not always good. Especially if it is long and a decent current will flow through it. If the copper on the workpiece is of high quality, without sins, then it is enough to degrease the surface.

Deposition of photoresist on the surface of the workpiece

We place the board on a horizontal or slightly inclined surface and apply the composition from an aerosol package from a distance of about 20 cm. Remember that the most important enemy in this case is dust. Every particle of dust on the surface of the workpiece is a source of problems. To create a uniform coating, spray the spray in a continuous zigzag motion, starting from the top left corner. Do not overspray as this causes unwanted streaks and results in uneven coating thickness requiring longer exposure times. In summer, when the ambient temperature is high, a re-treatment may be necessary, or it may be necessary to spray the aerosol from a shorter distance to reduce evaporation losses. When spraying, do not tilt the can too much this leads to an increased consumption of propellant gas and as a result the aerosol can stops working, although there is still photoresist in it. If you get unsatisfactory results with spray coating of photoresist, use spin coating. In this case, the photoresist is applied to a board mounted on a rotating table with a drive of 300-1000 rpm. After finishing the coating, the board should not be exposed to strong light. By the color of the coating, you can approximately determine the thickness of the applied layer:

  • light gray blue 1-3 microns;
  • dark gray blue 3-6 microns;
  • blue 6-8 microns;
  • dark blue over 8 microns.

On copper, the color of the coating may have a greenish tinge.

The thinner the coating on the workpiece, the better the result.

I always apply photoresist on a centrifuge. In my centrifuge, the rotation speed is 500-600 rpm. Fastening should be simple, clamping is done only at the ends of the workpiece. We fix the workpiece, start the centrifuge, spray on the center of the workpiece and observe how the photoresist spreads over the surface in a thin layer. By centrifugal forces, excess photoresist will be thrown off the future PP, so I highly recommend providing a protective wall so as not to turn the workplace into a pigsty. I use an ordinary pan, in the bottom of which a hole is made in the center. The axis of the electric motor passes through this hole, on which a mounting platform in the form of a cross of two aluminum rails is installed, along which the ears of the workpiece clamp “run”. The ears are made of aluminum corners clamped on the rail with a wing nut. Why aluminum? Small specific gravity and, as a result, less runout when the center of mass of rotation deviates from the center of rotation of the centrifuge axis. The more precisely the workpiece is centered, the less beating will be due to the eccentricity of the mass and the less effort will be required to rigidly fasten the centrifuge to the base.

Photoresist applied. Let it dry for 15-20 minutes, turn the workpiece over, apply a layer on the second side. We give another 15-20 minutes to dry. Do not forget that direct sunlight and fingers on the working sides of the workpiece are unacceptable.

Tanning of photoresist on the workpiece surface

We place the workpiece in the oven, gradually bring the temperature to 60-70 ° C. At this temperature we maintain 20-40 minutes. It is important that nothing touches the surfaces of the workpiece only touching the ends is allowed.

Alignment of the upper and lower photomasks on the surfaces of the workpiece

On each of the photomasks (upper and lower) there should be marks, according to which 2 holes must be made on the workpiece to match the layers. The farther apart the marks, the higher the alignment accuracy. I usually place them diagonally across the templates. According to these marks on the workpiece, using a drilling machine, we drill two holes strictly at 90 ° (the thinner the holes, the more accurate the alignment - I use a 0.3 mm drill) and combine the templates along them, not forgetting that the template must be applied to the photoresist the side that was printed on. We press the templates to the workpiece with thin glasses. It is preferable to use quartz glasses they transmit ultraviolet better. Plexiglas (plexiglass) gives even better results, but it has an unpleasant scratching property, which will inevitably affect the quality of the PP. For small PCB sizes, you can use a transparent cover from the CD packaging. In the absence of such glasses, ordinary window glass can also be used, increasing the exposure time. It is important that the glass is even, ensuring that the photomasks fit evenly on the workpiece, otherwise it will not be possible to obtain high-quality track edges on the finished PCB.


A blank with a photomask under plexiglass. We use the box from under the CD.

Exposure (flare)

The time required for exposure depends on the thickness of the photoresist layer and the intensity of the light source. POSITIV 20 photoresist varnish is sensitive to ultraviolet rays, the maximum sensitivity falls on the area with a wavelength of 360-410 nm.

It is best to expose under lamps whose radiation range is in the ultraviolet region of the spectrum, but if you do not have such a lamp, ordinary powerful incandescent lamps can be used, increasing the exposure time. Do not start illumination until the illumination from the source stabilizes it is necessary that the lamp warms up for 2-3 minutes. The exposure time depends on the thickness of the coating and is usually 60-120 seconds when the light source is located at a distance of 25-30 cm. The glass plates used can absorb up to 65% of ultraviolet, so in such cases it is necessary to increase the exposure time. Best results are achieved with transparent plexiglass plates. When using photoresist with a long shelf life, the exposure time may need to be doubled - remember: photoresists are subject to aging!

Examples of using different light sources:


UV lamps

We expose each side in turn, after the exposure we let the blank stand for 20-30 minutes in a dark place.

Development of the exposed workpiece

We develop in NaOH (caustic soda) solution see the beginning of the article for details at a solution temperature of 20-25°C. If there is no manifestation up to 2 minutes small O exposure time. If it appears well, but useful areas are also washed off you are too smart with the solution (the concentration is too high) or the exposure time is too long with this radiation source or the photomask is of poor quality insufficiently saturated printed black color allows ultraviolet light to illuminate the workpiece.

When developing, I always very carefully, effortlessly “roll” a cotton swab on a glass rod in those places where the exposed photoresist should be washed off, this speeds up the process.

Washing the workpiece from alkali and residues of exfoliated exposed photoresist

I do this under a faucet—normal tap water.

Retanning photoresist

We place the workpiece in the oven, gradually raise the temperature and at a temperature of 60-100 ° C we hold for 60-120 minutes the pattern becomes strong and solid.

Checking the development quality

For a short time (for 5-15 seconds) we immerse the workpiece in a solution of ferric chloride heated to a temperature of 50-60 ° C. Rinse quickly with running water. In places where there is no photoresist, intensive etching of copper begins. If a photoresist is accidentally left somewhere, carefully mechanically remove it. It is convenient to do this with a conventional or ophthalmic scalpel, armed with optics (soldering glasses, loupes A watchmaker, loop A on a tripod, microscope).

Etching

We pickle in a concentrated solution of ferric chloride with a temperature of 50-60°C. It is desirable to ensure continuous circulation of the pickling solution. We gently “massage” badly etched places with a cotton swab on a glass rod. If the ferric chloride is freshly prepared, the pickling time usually does not exceed 5-6 minutes. We wash the workpiece with running water.


Board etched

How to prepare a concentrated solution of ferric chloride? We dissolve FeCl 3 in slightly (up to 40 ° C) heated water until it ceases to dissolve. Filter the solution. You need to store in a dark, cool place in an airtight non-metallic package in glass bottles, for example.

Removing unwanted photoresist

We wash off the photoresist from the tracks with acetone or a solvent for nitro-paints and nitro-enamels.

Hole drilling

It is advisable to select the diameter of the point of the future hole on the photomask in such a way that it would be convenient to drill later. For example, with the required hole diameter of 0.6-0.8 mm, the dot diameter on the photomask should be about 0.4-0.5 mm in this case, the drill will center well.

It is advisable to use tungsten carbide coated drills: HSS drills wear out very quickly, although steel can be used to drill large diameter single holes (greater than 2 mm), since tungsten carbide coated drills of this diameter are too expensive. When drilling holes with a diameter of less than 1 mm, it is better to use a vertical machine, otherwise your drills will break quickly. If you drill with a hand drill distortions are inevitable, leading to inaccurate joining of holes between layers. The downward movement on a vertical drilling machine is the most optimal in terms of tool loading. Carbide drills are made with a rigid (i.e., the drill exactly fits the diameter of the hole) or thick (sometimes called "turbo") shank, having a standard size (usually 3.5 mm). When drilling with carbide-coated drills, it is important to firmly fix the PCB, since such a drill, when moving up, can lift the PCB, skew the perpendicularity and tear out a piece of the board.

Small diameter drills are usually inserted into either a collet chuck (various sizes) or a three-jaw chuck. For precise fixing, a three-jaw chuck is not the best option, and a small drill size (less than 1 mm) quickly grooves in the clamps, losing a good hold. Therefore, for drills with a diameter of less than 1 mm, it is better to use a collet chuck. Just in case, get an extra set containing spare collets for each size. Some inexpensive drills are made with plastic collets - throw them away and buy metal ones.

To obtain acceptable accuracy, it is necessary to properly organize the workplace, that is, firstly, to ensure good lighting of the board when drilling. To do this, you can use a halogen lamp, attaching it to a tripod to be able to choose a position (illuminate the right side). Secondly, raise the work surface about 15 cm above the countertop for better visual control over the process. It would be nice to remove dust and chips during the drilling process (you can use a regular vacuum cleaner), but this is not necessary. It should be noted that the dust from fiberglass generated during drilling is very caustic and irritates the skin if it comes into contact with it. And finally, when working, it is very convenient to use the foot switch of the drilling machine.

Typical hole sizes:

  • vias 0.8 mm or less;
  • integrated circuits, resistors, etc. 0.7-0.8 mm;
  • large diodes (1N4001) 1.0 mm;
  • contact blocks, trimmers up to 1.5 mm.

Try to avoid holes with a diameter of less than 0.7 mm. Always keep at least two spare drills 0.8 mm or less, as they always break just at the moment when you urgently need to order. Drills 1mm and larger are much more reliable, although it would be nice to have spare ones for them. When you need to make two identical boards, you can drill them at the same time to save time. In this case, it is necessary to very carefully drill holes in the center of the pad near each corner of the PCB, and for large boards, holes located close to the center. Lay the boards on top of each other and, using the 0.3mm centering holes in two opposite corners and the pins as pegs, secure the boards against each other.

If necessary, you can countersink holes with drills of a larger diameter.

Copper tinning on PP

If you need to irradiate the tracks on the PCB, you can use a soldering iron, soft low-melting solder, alcohol-rosin flux and coaxial cable braid. With large volumes, they are tinned in bathtubs filled with low-temperature solders with the addition of fluxes.

The most popular and simple melt for tinning is the low-melting alloy "Rose" (tin 25%, lead 25%, bismuth 50%), the melting point of which is 93-96 ° C. The board is placed with tongs under the level of the liquid melt for 5-10 seconds and, having taken it out, it is checked whether the entire copper surface is covered evenly. If necessary, the operation is repeated. Immediately after removing the board from the melt, its residues are removed either with a rubber squeegee or by sharp shaking in a direction perpendicular to the plane of the board, while holding it in the clamp. Another way to remove residues of the Rose alloy is to heat the board in an oven and shake it. The operation can be repeated to achieve a mono-thick coating. To prevent oxidation of the hot melt, glycerin is added to the tinning tank so that its level covers the melt by 10 mm. After the end of the process, the board is washed from glycerin in running water. Attention! These operations involve working with installations and materials that are under the influence of high temperature, therefore, to prevent burns, it is necessary to use protective gloves, goggles and aprons.

The tin-lead tinning operation proceeds similarly, but the higher melt temperature limits the scope of this method in handicraft production.

Do not forget to clean the board from flux after tinning and degrease thoroughly.

If you have a large production you can use chemical tinning.

Applying a protective mask

The operations with applying a protective mask exactly repeat everything that was written above: we apply a photoresist, dry, tan, center the photomasks of the masks, expose, develop, wash and tan again. Of course, we skip the steps with checking the quality of development, etching, removing photoresist, tinning and drilling. At the very end, we tan the mask for 2 hours at a temperature of about 90-100 ° C it will become strong and hard, like glass. The formed mask protects the surface of the PCB from external influences and protects against theoretically possible short circuits during operation. It also plays an important role in automatic soldering does not allow the solder to “sit down” on neighboring areas, closing them.

That's it, the double-sided printed circuit board with the mask is ready.

I had to make PP in this way with the width of the tracks and the step between them up to 0.05 mm (!). But this is a piece of jewelry. And without much effort, you can make PP with a track width and a step between them of 0.15-0.2 mm.

On the board shown in the photographs, I did not apply a mask there was no such need.


Printed circuit board in the process of mounting components on it

And here is the device itself, for which the software was made:

This is a cellular telephone bridge that allows you to reduce the cost of mobile services by 2-10 times for this it was worth messing around with PP;). The PCB with soldered components is in the stand. Previously, there was an ordinary charger for mobile phone batteries.

Additional Information

Hole plating

At home, you can even metallize holes. To do this, the inner surface of the holes is treated with a 20-30% solution of silver nitrate (lapis). Then the surface is cleaned with a squeegee and the board is dried in the light (you can use a UV lamp). The essence of this operation is that under the action of light, silver nitrate decomposes, and inclusions of silver remain on the board. Next, copper is chemically precipitated from the solution: copper sulfate (copper sulfate) 2 g, sodium hydroxide 4 g, ammonia 25% 1 ml, glycerin 3.5 ml, formalin 10% 8-15 ml, water 100 ml. The shelf life of the prepared solution is very short it is necessary to prepare immediately before use. After the copper is deposited, the board is washed and dried. The layer is obtained very thin, its thickness must be increased to 50 microns by galvanizing.

Electroplating solution for copper plating:
For 1 liter of water, 250 g of copper sulfate (copper sulfate) and 50-80 g of concentrated sulfuric acid. The anode is a copper plate suspended parallel to the part to be coated. The voltage should be 3-4 V, current density 0.02-0.3 A / cm 2, temperature 18-30 ° C. The lower the current, the slower the metallization process, but the better the resulting coating.


Fragment of the printed circuit board, where the metallization is visible in the hole

Homemade photoresists

Photoresist based on gelatin and potassium bichromate:
First solution: pour 15 g of gelatin into 60 ml of boiled water and leave to swell for 2-3 hours. After swelling of the gelatin, place the container in a water bath at a temperature of 30-40 ° C until the gelatin is completely dissolved.
The second solution: in 40 ml of boiled water, dissolve 5 g of potassium dichromate (chromic peak, bright orange powder). Dissolve in low ambient light.
Pour the second into the first solution with vigorous stirring. Add a few drops of ammonia to the resulting mixture with a pipette until a straw color is obtained. The photographic emulsion is applied to the prepared board in very low light. The board dries to "tack" at room temperature in complete darkness. After exposure, wash the board in low diffused light in warm running water until the untanned gelatin is removed. To better evaluate the result, you can stain areas with unremoved gelatin with a solution of potassium permanganate.

Advanced Homemade Photoresist:
First solution: 17 g of wood glue, 3 ml of an aqueous solution of ammonia, 100 ml of water, leave to swell for a day, then heat in a water bath at 80 ° C until completely dissolved.
Second solution: 2.5 g potassium dichromate, 2.5 g ammonium dichromate, 3 ml aqueous ammonia solution, 30 ml water, 6 ml alcohol.
When the first solution has cooled to 50°C, pour the second solution into it with vigorous stirring and filter the resulting mixture ( this and subsequent operations must be carried out in a darkened room, sunlight is unacceptable!). The emulsion is applied at a temperature of 30-40°C. Further as in the first recipe.

Photoresist based on ammonium dichromate and polyvinyl alcohol:
We prepare a solution: polyvinyl alcohol 70-120 g / l, ammonium dichromate 8-10 g / l, ethyl alcohol 100-120 g / l. Avoid bright light! Apply in 2 coats: first coat drying 20-30 minutes at 30-45°C second coat drying 60 minutes at 35-45°C. Developer 40% ethanol solution.

Chemical tinning

First of all, the board must be decapitated in order to remove the formed copper oxide: 2-3 seconds in a 5% hydrochloric acid solution, followed by rinsing in running water.

It is enough to simply carry out chemical tinning by immersing the board in an aqueous solution containing tin chloride. The release of tin on the surface of the copper coating occurs when immersed in a solution of tin salt, in which the copper potential is more electronegative than the coating material. A change in the potential in the desired direction is facilitated by the introduction of a complexing additive thiocarbamide (thiourea) into the tin salt solution. Solutions of this type have the following composition (g/l):

Among the listed solutions, solutions 1 and 2 are the most common. Sometimes, as a surfactant for the 1st solution, it is proposed to use Progress detergent in an amount of 1 ml / l. The addition of 2-3 g/l of bismuth nitrate to the 2nd solution leads to the precipitation of an alloy containing up to 1.5% bismuth, which improves the solderability of the coating (prevents aging) and greatly increases the shelf life before soldering the components of the finished PP.

To preserve the surface, aerosol sprays based on fluxing compositions are used. After drying, the varnish applied to the surface of the workpiece forms a strong, smooth film that prevents oxidation. One of the popular substances is "SOLDERLAC" from Cramolin. Subsequent soldering is carried out directly on the treated surface without additional varnish removal. In especially critical cases of soldering, the varnish can be removed with an alcohol solution.

Artificial tinning solutions deteriorate over time, especially when exposed to air. Therefore, if you do not often have large orders, then try to prepare at once a small amount of solution, sufficient to tin the required amount of PP, and store the remaining solution in a closed container (bottles of the type used in the photograph are ideal, which do not let air through). It is also necessary to protect the solution from contamination, which can greatly degrade the quality of the substance.

In conclusion, I want to say that it is still better to use ready-made photoresists and not bother with plating holes at home - you still won’t get great results.

Many thanks to the candidate of chemical sciences Filatov Igor Evgenievich for advice on chemistry-related matters.
I also want to express my gratitude Igor Chudakov.

Recently, radio electronics as a hobby in the world is gaining popularity, people are becoming interested in creating electronic devices with their own hands. There are a huge number of circuits on the Internet, from simple to complex, performing various tasks, so everyone can find in the world of radio electronics what they like.

An integral part of any electronic device is the printed circuit board. It is a plate of dielectric material, on which copper conductive tracks are applied that connect electronic components. Each of those who wish to learn how to assemble electrical circuits in a beautiful way must learn how to make these same printed circuit boards.

There are computer programs that allow you to draw a pattern of printed circuit board tracks in a convenient interface, the most popular of them is. The layout of the printed circuit board is carried out in accordance with the circuit diagram of the device, there is nothing complicated in this, it is enough just to connect the necessary parts with tracks. In addition, many circuit diagrams of electronic devices on the Internet already come with ready-made printed circuit board drawings.

A good printed circuit board is the key to a long and happy operation of the device, so you should try to make it as accurately and efficiently as possible. The most common method of making printed ones at home is the so-called "", or "laser-ironing technology". It has gained wide popularity because it does not take much time, does not require scarce ingredients and is not so difficult to learn. Briefly, LUT can be described as follows: let's say there is a pattern of tracks drawn on a computer. Next, this pattern must be printed on special thermal transfer paper, transferred to a textolite, then etched off excess copper from the board, drilled holes in the right places and tinned the tracks. Let's break down the whole process step by step:

Printing a board pattern

1) Printing a pattern on thermal transfer paper. You can buy such paper, for example, on Aliexpress, where it costs mere pennies - 10 rubles per A4 sheet. Instead, you can use any other glossy paper, for example, from magazines. However, the quality of toner transfer from such paper may be much worse. Some use Lomond glossy photo paper, a good option, if not for the price - such photo paper costs much more. I recommend trying to print the drawing on different papers, and then compare with which one you get the best result.

Another important point when printing a picture is the printer settings. It is imperative to turn off toner saving, but the density should be set to the maximum, because the thicker the toner layer, the better for our purposes.

You also need to take into account such a moment that the picture will be transferred to the textolite in a mirror image, so you need to foresee whether or not you need to mirror the picture before printing. This is especially critical on boards with microcircuits, because the other side cannot supply them.

Preparing textolite for transferring a pattern onto it

2) The second stage is the preparation of the textolite for transferring the drawing onto it. Most often, textolite is sold in segments 70x100 or 100x150 mm in size. It is necessary to cut off a piece suitable for the dimensions of the board, with a margin of 3-5 mm along the edges. It is most convenient to cut textolite with a hacksaw for metal or a jigsaw, in extreme cases it can be cut off with scissors for metal. Then, this piece of textolite should be wiped with fine sandpaper or a hard eraser. Minor scratches form on the surface of the copper foil, this is normal. Even if initially the textolite looks perfectly even, this step is necessary, otherwise it will be difficult to tin it later. After sanding, the surface must be wiped with alcohol or a solvent to wash off dust and greasy marks from hands. After that, you can not touch the copper surface.


Transferring the pattern to the prepared textolite

3) The third stage is the most responsible. It is necessary to transfer the pattern printed on thermal transfer paper to the prepared textolite. To do this, cut the paper as shown in the photo, leaving reserves at the edges. We put paper on a flat wooden board with the pattern up, then we apply textolite on top, with copper to the paper. We bend the edges of the paper as if it were hugging a piece of textolite. After that, carefully flip the sandwich so that the paper is on top. We check that the drawing has not shifted anywhere relative to the textolite and put a clean piece of ordinary office white paper on top so that it covers the entire sandwich.

Now it remains only to heat the whole thing thoroughly, and all the toner from the paper will be on the textolite. You need to attach a heated iron on top and heat the sandwich for 30-90 seconds. The heating time is selected experimentally and largely depends on the temperature of the iron. If the toner went badly and remained on the paper, you need to keep it longer, if, on the contrary, the tracks are transferred, but smeared, this is a clear sign of overheating. It is not necessary to put pressure on the iron, its own weight is enough. After warming up, you need to remove the iron and iron the workpiece that has not yet cooled down with a cotton swab, in case the toner did not pass well when ironing with an iron in some places. After that, it remains only to wait until the future board cools down and remove the thermal transfer paper. It may not work the first time, it does not matter, because experience comes with time.

PCB etching

4) The next step is etching. Any area of ​​copper foil that is not covered by the toner must be removed, leaving the copper under the toner untouched. First you need to prepare a solution for etching copper, the simplest, most affordable and cheapest option is a solution of citric acid, salt and hydrogen peroxide. In a plastic or glass container, stir one to two tablespoons of citric acid and a teaspoon of table salt into a glass of water. Proportions do not play a big role, you can pour it on the eye. Mix thoroughly and the solution is ready. You need to put a board in it, tracks down to speed up the process. You can also slightly warm the solution, this will further increase the speed of the process. After about half an hour, all excess copper will be etched away and only tracks will remain.

Rinse toner from tracks

5) The hardest part is over. At the fifth stage, when the board is already etched, you need to wash off the toner from the tracks with a solvent. The most affordable option is female nail polish remover, it costs a penny and almost every woman has it. Common solvents such as acetone can also be used. I use petroleum solvent, although it stinks a lot, it does not leave any black stains on the board. In extreme cases, you can remove the toner by rubbing the board well with sandpaper.

Drilling holes on the board

6) Drilling holes. You will need a small drill with a diameter of 0.8 - 1 mm. Ordinary high speed steel drills quickly become dull on PCB, so it is best to use tungsten carbide drills, although they are more fragile. I drill the boards with an old hair dryer motor with a small collet chuck, and the holes come out clean and burr-free. Unfortunately, at the most inopportune moment, the last carbide drill broke, so only half of the holes were drilled in the photographs. The rest can be drilled later.

Tin tracks

7) It remains only to tin the copper tracks, i.e. cover with solder. Then they will not oxidize over time, and the board itself will become beautiful and shiny. First you need to apply flux to the tracks, and then quickly crawl over them with a soldering iron with a drop of solder. You should not apply an excessively thick layer of solder, then the holes may close, and the board will look sloppy.

This completes the PCB manufacturing process, now you can solder parts into it. The material was provided for the Radio Scheme website by Mikhail Gretsky, [email protected]

Discuss the article MANUFACTURING OF PRINTED BOARDS WITH LUT

Since I'm an engineering student, I often make projects at home with fairly simple electronic circuits, and for this I often make PCBs myself.

What is a printed circuit board?

A printed circuit board (PCB) is used for mechanical mounting of radio components and their electrical connection using a conductive pattern, contact pads and other components etched on the copper layer of a laminated plate.
There are pre-designed copper tracks on the PCB. Properly designing connections through these traces reduces the number of wires used and therefore the amount of damage caused by broken connections. The components are mounted on the PCB by soldering.

Creation methods

There are three main ways to make printed circuit boards with your own hands:

  1. LUT PCB manufacturing technology
  2. Laying tracks manually
  3. Etching on a laser machine

The laser etching method is industrial, so I will talk more about the first two manufacturing methods.

Step 1: Create the PCB layout

Typically, wiring is done by converting the circuit diagram using special programs. There are many free programs in the public domain, for example:

I created the layout using the first program.

Do not forget in the image settings (File - Export - Image) select DPIG 1200 for the best image quality.

Step 2: Board materials

(text on photo):

  • Magazines or promotional brochures
  • Laser printer
  • regular iron
  • Copper Coated Laminate for PP
  • pickling solution
  • foam sponge
  • Solvent (e.g. acetone)
  • Wire in plastic insulation

You will also need: permanent marker, sharp knife, sandpaper, paper towels, cotton wool, old clothes.
I will explain the technology using the example of manufacturing a PP touch switch with IC555.

Step 3: Print out the wiring

Print the wiring diagram on a sheet of A4 glossy or photo paper on a laser printer. Do not forget:

  • You need to print the image in mirror image
  • Select "Print All Black" in both PCB design software and laser printer settings
  • Make sure the image will be printed on the glossy side of the paper.

Step 4: Cut out the board from the laminate


Cut out a piece of laminate sheet the same size as the board layout image.

Step 5: Sanding the Board

Scrub the foil side with a steel wool or the abrasive side of a dishwashing sponge. This is necessary to remove the oxide film and the photosensitive layer.
On a rough surface, the image fits better.

Step 6: Schematic Options




Option 1:
LUT: transfer of an image printed on a glossy layer of paper onto a foil layer of a laminate. Place the printed image on a horizontal surface with the toner facing up. Lay the board on top of the copper layer on the image. The image should be positioned exactly relative to the edges. Fasten the laminate and the image on both sides with tape so that the paper cannot move, the sticky layer of the tape should not get on the copper coating.

Option 2:
Marking the traces with a permanent marker: Using the printed wiring as a sample, mark the circuit on the copper layer of a piece of laminate, first with a pencil, then trace with a permanent black marker.

Step 7: Smoothing Out The Image



  • The printed image must be ironed. Heat up the iron to maximum temperature.
  • put a clean, unnecessary cloth on a flat wooden surface, put the future board on it with the copper layer up with the circuit image pressed against it.
  • on one side, press the board with a hand with a towel, on the other, press it with an iron. Hold the iron for 10 seconds, then start ironing with paper, pressing a little, for 5-15 minutes.
  • iron the edges well - with pressure, slowly moving the iron.
  • a long press works better than constantly ironing.
  • the toner should melt and stick to the copper layer.

Step 8: Cleaning the Board



After ironing, place it in warm water for about 10 minutes. The paper will get wet and can be removed. Remove paper at a low angle and preferably without residue.

Sometimes pieces of tracks are removed with paper.
The white rectangle in the photographs marks the place where the tracks were poorly transferred and then restored with a black permanent marker.

Step 9: Etching





When pickling, you need to be extremely careful.

  • put on rubber gloves or plastic-coated gloves first
  • cover the floor with newspapers just in case
  • fill the plastic box with water
  • add 2-3 teaspoons of ferric chloride powder to the water
  • soak the board in the solution for about 30 minutes
  • ferric chloride will react with copper and copper, not protected by a layer of toner, will go into solution
  • to check how the internal parts of the board are being etched, remove the board from the solution with pliers, if the inside has not yet been cleaned of copper, leave it in the solution for some more time.

Stir the solution lightly to make the reaction more active. The solution produces copper chloride and iron chloride.
Check every two to three minutes to see if all of the copper has been etched off the board.

Step 10: Safety





Do not touch the solution with bare hands, be sure to use gloves.
The photo shows how the etching takes place.

Step 11: Solution Disposal

The pickling solution is toxic to fish and other aquatic organisms.
Do not pour the used solution down the sink, it is illegal and can ruin the pipes.
Dilute the solution to reduce the concentration and only then drain into the public sewer.

Step 12: Finishing the Manufacturing Process




The photo shows for comparison two printed circuit boards made using a LUT and a permanent marker.

put a few drops of solvent (you can use nail polish remover) on a cotton swab and remove the remaining toner from the board, you should be left with only copper tracks. Proceed with care, then dry the board with a clean cloth. Cut the board to size and sand the edges with sandpaper.

Drill mounting holes and solder all components to the board.

Step 13: Conclusion

  1. Laser-ironing technology is a very effective way to make printed circuit boards at home. If you do everything carefully, each track will turn out clear.
  2. Routing with a permanent marker is limited by our artistic skills. This method is suitable for the simplest circuits, for something more complex it is better to make the board in the first way.