Making a printed circuit board. PCB layout

Sprint-Layout
The program with a simple and intuitive interface is designed for the design of printed circuit boards of low complexity. Used by radio electronics enthusiasts when creating boards for electronic devices to automate the design process.

Eagle
A popular computer program specially created for beginners and radio electronics enthusiasts. Allows you to draw electrical circuit diagrams and printed circuit boards of no more than average complexity.

The domestic Russian-language program is intended for both professionals and radio amateurs. Used to create boards manually or automatically. Distributed in 2 versions - free (with restrictions) and paid.

A free, easy-to-learn and operate program designed for manual design of circuit boards of low to medium complexity. In addition to the built-in library of electronic components, it is possible to create your own database, which has made it popular among radio amateurs.

Altium Designer
Professional software for creating a wide range of electronic boards and devices of varying complexity. Allows you to carry out the development and design of printed circuit boards at a high level. It is used in many industries dealing with electronic devices.

FreePCB
A software product that is widely used by professionals in the development and design of printed circuit boards of varying complexity. It is distributed free of charge, which allows the software to be used by many national enterprises and private companies that produce electronic devices.

Kicad
A free Russian-language professional program that allows you to develop printed circuit boards and electrical circuits of low, medium and high complexity. You can create boards and place components on them manually and automatically.

DesignSpark PCB
A free program that allows you to design electrical circuits and printed circuit boards of electronic devices at a professional level. The program is equipped with a powerful library of electronic components and has an auto-routing function.

PCB123
A software product with which amateurs and professionals can design and develop circuits and boards of any complexity with the creation of a three-dimensional image. The program is distributed free of charge.

TopoR
A paid, high-performance program released by a domestic manufacturer, designed for the design and manufacture of boards of any complexity. The appearance of the resulting board can be clearly seen in a three-dimensional image, which can be constructed in the same program.

EDWinXP
Paid professional software used for designing boards and developing electronic devices of varying complexity. The program can be downloaded for free, but the duration of such a program is limited (14 days).

P-CAD
Powerful and one of the very first professional automated programs for designing printed circuit boards. Allows you to design boards of any complexity. The version of the program currently in use is one that was released in 2006.

A paid professional program designed for designing both light and complex single-sided, double-sided and multilayer boards. The functions available in the program allow you to simulate, carry out various tests and fully prepare the board for production. There is a trial version of the program, which is limited by the number of days of its use (30).

A printed circuit board is a structural element that consists of a dielectric base and copper conductors, which are deposited on the base in the form of metallized sections. It provides the connection of all radio-electronic elements of the circuit.

A printed circuit board has a number of advantages compared to volumetric (hinged) installation using cables and wires:

• high installation density of radio components and their connections, resulting in a significant reduction in the dimensions and weight of the product;
• production of conductors and shielding surfaces, as well as radioelements in a single technological cycle;
• stability, repeatability of such characteristics as capacitance, conductivity, inductance;
• high performance and noise immunity of circuits;
• resistance to mechanical and climatic influences;
• standardization and unification of technological and design solutions;
• reliability of components, blocks and the device itself as a whole;
• increased manufacturability as a result of comprehensive automation of assembly work and control and regulatory actions;
• low labor intensity, material consumption and cost.

The printed circuit board also has disadvantages, but they are very few: limited maintainability and high complexity of adding design changes.

The elements of such boards include: a dielectric base, a metallized coating, which is a pattern of printed conductors, contact pads; fixing and mounting holes.

Requirements that GOST imposes on these products

• Printed circuit boards must have a dielectric base that is uniform in color, which must be monolithic in structure and free from internal bubbles, cavities, foreign inclusions, cracks, chips, and delaminations. However, single scratches, inclusions of metal, traces of a single removal of an unetched area, as well as the manifestation of the structure are allowed, which does not change the electrical parameters of the product and does not reduce the permissible distance between the elements of the design.
• The pattern is clear, with a smooth edge, without swelling, tears, peeling, or tool marks. Minor local mordants are allowed, but not more than five points per square decimeter, provided that the remaining width of the path corresponds to the minimum allowable; scratches up to six millimeters long and up to 25 microns deep.

To improve corrosion characteristics and increase solderability, the surface of the board is coated with an electrolytic composition, which must be continuous, without peeling, ruptures or burns. Fixing and mounting holes must be located in accordance with the drawing. It is allowed to have deviations determined by the accuracy class of the board. In order to improve the reliability of soldering, a layer of copper is sprayed onto all internal surfaces of the mounting holes, the thickness of which must be at least 25 microns. This process is called metallization of holes.

What are PCB classes? This concept refers to the accuracy classes of board manufacturing; they are provided for by GOST 23751-86. Depending on the density of the pattern, the printed circuit board has five options, the choice of which is determined by the level of technical equipment of the enterprise. The first and second classes do not require high-precision equipment and are considered cheap to produce. The fourth and fifth classes require special materials, specialized equipment, ideal cleanliness in production premises, and maintenance of temperature conditions. Domestic enterprises mass produce printed circuit boards of the third accuracy class.

Basic rules for board development

It is most convenient to design printed circuit boards in a 1:1 scale on graph paper or other material on which a grid is applied in 5 mm increments (for example, on a notebook sheet). It is advisable to place all holes for pins of parts in the printed circuit board in grid nodes, which corresponds to the pitch
2.5mm on a real board. The terminals of most microcircuits in a plastic case, many transistors and other radio components are located with this pitch. Less
The distance between holes should be chosen only in cases where it is absolutely necessary.
First you need to roughly arrange the parts. First of all, draw points for the pins of the microcircuit, then place small elements - resistors, capacitors,
and then the big ones - relays, etc. Their placement is usually related to the overall design of the device, determined by the size! the existing case or free space in it. Often, especially
Especially when developing portable devices, the dimensions of the case are determined by the results of the printed circuit board layout. Sometimes it is necessary to redo the pattern of printed circuit wires
nicks several times to get the desired result of minification and functionality.
If your homemade product has no more than five microcircuits, you can usually place all printed conductors on one side of the board and make do with a small number of test leads.
jumpers soldered on the parts side.

Attempts to produce a single-sided PCB for a larger number
digital chips lead to a sharp increase
labor-intensive wiring and an excessively large number of jumpers. In these
In some cases, it makes more sense to switch to a double-sided PCB.
We will call the side of the board where the
printed conductors, the side of the conductors, and the reverse -
side of the parts, even if on it together with the parts
Some of the conductors have been laid. A special case is presented by
boards in which both conductors and parts are located on
one side, and the parts are soldered to the conductors without
holes. Boards of this design are rarely used.
The microcircuits are placed so that all connections on the board
were as short as possible, and the number of jumpers was
minimal. During the wiring of conductors, mutual
The placement of microcircuits has to be changed more than once.
Drawing of printed conductors of analog devices
any complexity can usually be placed on one
side of the board. Analog devices that work with
weak signals, and digital on high-speed
microcircuits (for example, KR531, KR1531, K500, KR1554 series)
Regardless of the frequency of their operation, it is advisable to collect
on boards with double-sided foil. Toy foil
sides of the board where the parts are located will play a role
common wire and screen. The foil of the common wire should not be
use as a conductor for high current,
for example, from the power supply rectifier, from the output
steps, from the dynamic head.

Next, you can begin the actual wiring. It is better to measure and write down the dimensions of the spaces occupied by the elements in advance. MLT-0.125 resistors are installed nearby, observing
the distance between their axes is 2.5 mm, and between the holes for
the terminals of one resistor are 10 mm. Places are also marked
% for alternating resistors MLT-0.125 and MLT-0.25 or
two MLT-0.25 resistors, if slightly bent during installation
one from the other (place three such resistors close to
the board will no longer succeed). With the same distances between
the pins and axes of the elements are installed by the majority
small-sized diodes and capacitors KM-5 and KM-6, up to
KM-66 with a capacity of 2.2 µF. “Thick” parts (more than 2.5 mm)
should be alternated with “thin” ones. Distance between
the contact pads of a particular part can be increased,
if necessary.
In this work it is convenient to use a small plate -
template made of fiberglass or other material, in
in which, in increments of 2.5 mm, holes with a diameter of
1-1.1 mm. On it you can apply the possible
arrangement of elements relative to each other.
If resistors, diodes and other parts with axial
pins should be placed perpendicular to the printed circuit board, you can
significantly reduce its area, however, the pattern of printed
conductors will become more complicated. When wiring you should take into account
restrictions on the number of conductors that fit between
contact pads intended for soldering
terminals of radioelements. For most parts diameter
The holes for the leads can be 0.8 mm. Restrictions
per number of conductors for typical layout options
contact pads with holes of this diameter
are shown in Fig. 8.1 (grid corresponds to 2.5 mm pitch on the board).
Between the contact pads of the holes with
With a center-to-center distance of 2.5 mm, guide the conductor almost
it is forbidden. However, if one or both holes have such
there is no pad (for example, at unused pins
microcircuits), this can be done (see Fig. 8.1 - top center).
It is quite possible to lay a conductor between the contact
platform and the edge of the board, through which at a distance
2.5 mm passes through the center of this area (see Fig. 8.1 - right).

Microcircuits whose pins are located in
body planes (series 133, K134, etc.)" can be mounted,
providing for this purpose the appropriate foil
contact pads with a pitch of 1.25 mm, but this is noticeable
complicates both wiring and board manufacturing. More expedient
alternate soldering of microcircuit pins to rectangular ones
platforms from the parts side and to the round platforms through
holes - on the opposite side (Fig. 8.2 -
The width of the microcircuit pins is not shown to scale). Pay
here it is two-sided.

Similar microcircuits with long leads
(e.g. 100 series), can be mounted in the same way as
plastic, bending the leads and passing them into the holes
fees. In this case, the contact pads are located in
in a checkerboard pattern (Fig. 8.3).

When designing a double-sided board, you should try to leave as few connections as possible on the parts side. This will make it easier to correct possible errors, set up the device and, if necessary, upgrade it. A common wire and a power wire are laid under the microcircuit housings, but they need to be connected only to the power pins of the microcircuits. Conductors to the inputs of microcircuits connected to the power circuit or the common wire are laid on the side of the conductors, and so that they can be easily cut when setting up or improving the device. If the device is so complex that signal circuit conductors have to be laid on the component side, make sure that any of them is accessible for connection to it and cutting. When developing amateur radio double-sided printed circuit boards, one should strive to avoid special jumpers between the sides of the board, using for this purpose the contact pads of the corresponding pins of the mounted parts. In these cases, the leads are soldered on both sides of the board. On complex boards, it is sometimes convenient to solder some parts directly to the printed circuit conductors. When a solid layer of foil is used as a common wire, the holes for terminals that are not connected to this wire should be countersunk from the parts side. Typically, a unit assembled on a printed circuit board is connected to other units of the device using flexible conductors. In order not to damage the printed conductors during repeated soldering, it is advisable to make contact stands on the board at the connection points (it is convenient to use pin contacts with a diameter of 1 and 1.5 mm). The racks are inserted into holes drilled exactly to the diameter and soldered. On a double-sided PCB, the soldering pads for each stand must be on both sides. It is convenient to carry out preliminary wiring of conductors with a soft pencil on a sheet of smooth paper. The side of the printed conductors is drawn with solid lines, the reverse side - with dashed lines, so as not to get confused. Upon completion of the layout and adjustment of the drawing, place carbon paper under it with the ink layer facing up and use a red or green ballpoint pen to trace the contours of the board, as well as the conductors and holes related to the side of the parts. As a result, on the back of the sheet you will get a drawing of conductors for the side of the parts. Next, you should cut out a blank of the appropriate size from the foil material and mark it with a caliper using a grid with a pitch of 2.5 mm. By the way, it is convenient to choose the dimensions of the board in multiples of 2.5 mm. - in this case, you can mark it on four sides. If the board must have any cutouts, they are made after marking. The double-sided board is marked on the side where there are more conductors. After this, use a felt-tip pen to mark the centers of all the holes “in cells”, prick them with an awl and drill all the holes with a drill with a diameter of 0.8 mm. To drill circuit boards, it is convenient to use a homemade miniature electric drill, which can be bought on the radio market. Conventional steel drills become dull rather quickly when processing fiberglass; sharpen them with a small fine-grained stone without removing the drill from the chuck. After drilling the board, burrs are removed from the edges of the holes with a larger diameter drill or a fine-grained stone. The board is degreased by wiping with a cloth moistened with alcohol or acetone, after which, focusing on the position of the holes, a pattern of printed conductors is transferred to it using nitro paint in accordance with the drawing. A glass drawing board is usually used for this, but it is better to make a simple homemade drawing tool. To the end of the broken student's pen, solder an injection needle shortened to 10-15 mm with a diameter of 0.8 mm. The working part of the needle must be sanded with fine-grained sandpaper. Nitro paint is poured into the funnel of the instrument in drops and, carefully taking it into the lips, blow lightly so that the paint passes through the needle channel. After this, you just need to make sure that the funnel is at least half filled with paint. The required paint density is determined experimentally by the quality of the lines drawn. If necessary, it is diluted with acetone or solvent 647. If it is necessary to make the paint thicker, it is left for some time in an open container. First of all, the contact pads are drawn, then connections are made between them, starting from those areas where the conductors are closely located. After the drawing is basically ready, you should, if possible, expand the common wire and power conductors, which will reduce their resistance and inductance, and therefore increase the stability of the device. It is also advisable to increase the contact pads, especially those to which racks and large parts will be soldered. To protect large surfaces of the foil from the etching solution, they are sealed with any adhesive film. If you make a mistake when applying a drawing, do not rush to correct everything right away - lay the correct one over the incorrectly applied conductor, and remove the excess paint when finally correcting the drawing (this is done before the paint has dried). Using a sharp scalpel or razor, the area to be removed is cut along the borders, after which it is scraped out. There is no need to specially dry the nitro paint after applying the design. While you are fixing the board, wash the tool - the paint will dry.

To obtain the conductors after applying the design to the foil, the board must be etched. The main material for etching is a solution of ferric chloride. To obtain it, you need to pour about 3/4 of ferric chloride powder into a glass and fill it with warm water. For etching, use a glass or plastic container, such as a photographic cuvette. Place the board in the solution with the pattern facing up so that the entire surface of the board is covered with the solution. The etching process is accelerated if the vessel is shaken or heated. Pickling produces toxic fumes, so work either in a well-ventilated area or outdoors. Periodically check the condition of the board by lifting it for inspection with wooden or plastic sticks - metal tools and devices cannot be used for this purpose. Once you are sure that the foil in unprotected areas has completely disappeared, stop the etching process. Transfer the board, for example using a clothespin, under running water and rinse thoroughly, then dry it at room temperature. If you intend to reuse the solution, pour it into a tightly sealed container and store it in a cool, dark place. Please note that the effectiveness of the solution decreases with repeated use. When working with ferric chloride solution, remember that it should not get on your hands or other exposed parts of the body, as well as on the surfaces of bathtubs and sinks, since the latter may leave yellow stains that are difficult to wash off. A solution of ferric chloride can be made in another way: treat iron filings with hydrochloric acid. Take 25 parts by weight of 10 percent hydrochloric acid and mix with one part by weight of iron filings. Keep the mixture in a tightly sealed container in a dark place for 5 days. When pouring the solution into a vessel for etching, do not shake it: the sediment should remain in the container in which the solution was prepared. The duration of the board etching process in a ferric chloride solution is usually 40-50 minutes and depends on the concentration of the solution, its temperature, and the thickness of the foil. Solutions for etching boards can be prepared not only based on ferric chloride. For many radio amateurs, an aqueous solution of copper sulfate and table salt may be more accessible. It is not difficult to prepare - dissolve 4 tablespoons of table salt and 2 tablespoons of copper sulfate crushed into powder in 500 ml of hot water (temperature about 80 °C). The effectiveness of the solution increases if it is kept for 2-3 weeks. The etching time of the board in such a solution is three hours or more. A significant reduction in the etching period can be achieved by using acid-based solutions. The process of etching the board, for example, in a concentrated solution of nitric acid, lasts only 5-7 minutes. After etching, wash the board thoroughly with soap and water. Good results are obtained by using a solution of hydrochloric acid and hydrogen peroxide. To prepare it, take 20 parts (by volume) of hydrochloric acid with a density of 1.19 g/cm3, 40 parts of pharmaceutical hydrogen peroxide and 40 parts of water. First mix water with hydrogen peroxide, then carefully add the acid. In this case, the drawing is done with nitro paint. Pour acid-based solutions into glass or ceramic containers; work with them only in well-ventilated areas. Of interest is the method of galvanic etching of boards. To do this, you will need a DC source with a voltage of 25-30 V and a concentrated solution of table salt. Using an alligator clip, connect the positive pole of the source to the unpainted areas of the board’s foil, and attach a cotton swab, generously soaked in salt solution, to the exposed and looped end of the wire coming from the negative pole of the source. Move it along the surface of the board, lightly pressing it against the foil. The movement of the tampon should resemble the drawing of the number 8. In this case, the foil will be “washed off,” as it were. Change the cotton whenever it gets dirty.

Radio amateurs advise

Professional radio amateurs offer us the ability to make printed circuit boards quite quickly using a laser printer (or copier), an iron and film from Techniks or DynaArt (everything else - foil PCB, ferric chloride, drills - as usual). Film and iron are needed to transfer the printed circuit board design to copper. Having prepared a drawing of a printed circuit board using any package for developing printed circuit boards or some editor for drawing pictures, we make a test print. We display an image of the printed circuit board on a blank sheet of paper. Then we cut out a fragment from the film with a margin of about 1 cm on each side. Glue it with tape with the glossy side to the paper on top of the drawing. We insert the sheet of film into the printer and print again. We get a film with an image of a printed circuit board printed on it. Then we prepare the textolite. In my opinion, the Surzha cleaning agent is excellent for this (do not neglect basic safety standards - use rubber gloves). After washing and drying the board, apply a film of toner to it and iron it with an iron for 1.5-4 minutes at a temperature of 135-160 °C. When the board cools down, carefully remove the film under running water - the drawing is transferred. We inspect the board and, if there are any flaws, correct them with an alcohol marker. Now you can etch using a ferric chloride solution. You can clean the toner from the finished board with an old blade, using it as a scraper. The same method is suitable for the production of double-sided printed circuit boards. To combine layers, you can use the following trick: draw three anchor points on both layers in the same place - best along the perimeter of the board. After transferring the first layer, drill holes at these points. We combine the points on the film for the second side with the holes. This option is not suitable for Techniks film, since it is opaque. You can do this: add 4 parallel lines to the printed circuit board drawing in both layers at a distance of 5 mm from the board border. After transferring the first layer, apply a ruler over the line and extend it to the end of the workpiece. We make a mark on the ends of the workpiece and transfer the lines to the other side of the board. The second film is combined with the lines - you can transfer the second layer. The quality of these boards is very good. There is a technology for manufacturing printed circuit boards using ordinary drawing tracing paper. It differs little from the technology with special film. Before use, the tracing paper must be passed through the printer or ironed to remove heat shrinkage. Then everything is the same. After cooling, place the board with toner and tracing paper in warm water, wait until the tracing paper gets wet, and carefully roll up the paper with a cloth. After this we correct it with a marker. It should be noted that the quality of the boards is somewhat worse, but much cheaper. To apply a design to the board, you can also use an alcohol marker (preferably a German one), but this is only suitable for simple boards in a single copy. The quality is the same as with tracing paper, but the difficulties are immeasurably greater. But for simple things it will do.

Layout of radio components on the board

Printed circuit board (PCB, or printed wiring board, PWB) is a dielectric plate on the surface and/or volume of which electrically conductive circuits of an electronic circuit are formed. A printed circuit board is designed to electrically and mechanically connect various electronic components. Electronic components on a printed circuit board are connected by their terminals to elements of a conductive pattern, usually by soldering.

Unlike surface mounting, on a printed circuit board the electrically conductive pattern is made of foil, located entirely on a solid insulating base. The printed circuit board contains mounting holes and pads for mounting leaded or planar components. In addition, printed circuit boards have vias for electrically connecting sections of foil located on different layers of the board. On the outside of the board, a protective coating (“solder mask”) and markings (supporting drawing and text according to the design documentation) are usually applied.

Depending on the number of layers with an electrically conductive pattern, printed circuit boards are divided into:

single-sided (OSP): there is only one layer of foil glued to one side of the dielectric sheet.

double-sided (DPP): two layers of foil.

multilayer (MLP): foil not only on two sides of the board, but also in the inner layers of the dielectric. Multilayer printed circuit boards are made by gluing together several single-sided or double-sided boards.

As the complexity of the designed devices and installation density increases, the number of layers on the boards increases.

The basis of the printed circuit board is a dielectric; the most commonly used materials are fiberglass and getinax. Also, the basis of printed circuit boards can be a metal base coated with a dielectric (for example, anodized aluminum); copper foil of the tracks is applied on top of the dielectric. Such printed circuit boards are used in power electronics for efficient heat removal from electronic components. In this case, the metal base of the board is attached to the radiator. The materials used for printed circuit boards operating in the microwave range and at temperatures up to 260 °C are fluoroplastic reinforced with glass fabric (for example, FAF-4D) and ceramics. Flexible circuit boards are made from polyimide materials such as Kapton.

What material will we use to make the boards?

The most common, affordable materials for making boards are Getinax and Fiberglass. Getinax paper impregnated with bakelite varnish, fiberglass textolite with epoxy. We will definitely use fiberglass!

Foil fiberglass laminate is sheets made from glass fabrics, impregnated with a binder based on epoxy resins and lined on both sides with copper electrolytic galvanic resistant foil 35 microns thick. Maximum permissible temperature from -60ºС to +105ºС. It has very high mechanical and electrical insulating properties and can be easily machined by cutting, drilling, stamping.

Fiberglass is mainly used single or double-sided with a thickness of 1.5 mm and with copper foil with a thickness of 35 microns or 18 microns. We will use one-sided fiberglass laminate with a thickness of 0.8 mm with a foil with a thickness of 35 microns (why will be discussed in detail below).

Methods for making printed circuit boards at home

Boards can be produced chemically and mechanically.

With the chemical method, in those places where there should be tracks (pattern) on the board, a protective composition (varnish, toner, paint, etc.) is applied to the foil. Next, the board is immersed in a special solution (ferric chloride, hydrogen peroxide and others) which “corrodes” the copper foil, but does not affect the protective composition. As a result, copper remains under the protective composition. The protective composition is subsequently removed with a solvent and the finished board remains.

The mechanical method uses a scalpel (for manual production) or a milling machine. A special cutter makes grooves on the foil, ultimately leaving islands with foil - the necessary pattern.

Milling machines are quite expensive, and the milling machines themselves are expensive and have a short resource. So we won't use this method.

The simplest chemical method is manual. Using a risograph varnish, we draw tracks on the board and then etch them with a solution. This method does not allow making complex boards with very thin traces - so this is not our case either.

The next method of making circuit boards is using photoresist. This is a very common technology (boards are made using this method at the factory) and is often used at home. There are a lot of articles and methods for making boards using this technology on the Internet. It gives very good and repeatable results. However, this is also not our option. The main reason is rather expensive materials (photoresist, which also deteriorates over time), as well as additional tools (UV illumination lamp, laminator). Of course, if you have a large-scale production of circuit boards at home - then photoresist is unrivaled - we recommend mastering it. It is also worth noting that the equipment and photoresist technology allows us to produce silk-screen printing and protective masks on circuit boards.

With the advent of laser printers, radio amateurs began to actively use them for the manufacture of circuit boards. As you know, a laser printer uses “toner” to print. This is a special powder that sinteres under temperature and sticks to the paper - the result is a drawing. The toner is resistant to various chemicals, which allows it to be used as a protective coating on the surface of copper.

So, our method is to transfer toner from paper to the surface of copper foil and then etch the board with a special solution to create a pattern.

Due to its ease of use, this method has become very widespread in amateur radio. If you type in Yandex or Google how to transfer toner from paper to a board, you will immediately find a term such as “LUT” - laser ironing technology. Boards using this technology are made like this: the pattern of the tracks is printed in a mirror version, the paper is applied to the board with the pattern on the copper, the top of this paper is ironed, the toner softens and sticks to the board. The paper is then soaked in water and the board is ready.

There are “a million” articles on the Internet about how to make a board using this technology. But this technology has many disadvantages that require direct hands and a very long time to adapt yourself to it. That is, you need to feel it. The payments don't come out the first time, they come out every other time. There are many improvements - using a laminator (with modification - the usual one does not have enough temperature), which allows you to achieve very good results. There are even methods for constructing special heat presses, but all this again requires special equipment. The main disadvantages of LUT technology:

overheating - the tracks spread out - become wider

underheating - the tracks remain on the paper

the paper is “fried” to the board - even when wet it is difficult to come off - as a result, the toner may be damaged. There is a lot of information on the Internet about what paper to choose.

Porous toner - after removing the paper, micropores remain in the toner - through them the board is also etched - corroded tracks are obtained

repeatability of the result - excellent today, bad tomorrow, then good - it is very difficult to achieve a stable result - you need a strictly constant temperature for warming up the toner, you need stable contact pressure on the board.

By the way, I was unable to make a board using this method. I tried to do it both on magazines and on coated paper. As a result, I even ruined the boards - the copper swelled due to overheating.

For some reason, there is unfairly little information on the Internet about another method of toner transfer - the cold chemical transfer method. It is based on the fact that toner is not soluble in alcohol, but is soluble in acetone. As a result, if you choose a mixture of acetone and alcohol that will only soften the toner, then it can be “re-glued” onto the board from paper. I really liked this method and immediately bore fruit - the first board was ready. However, as it turned out later, I could not find detailed information anywhere that would give 100% results. We need a method that even a child could make the board with. But the second time it didn’t work out to make the board, then again it took a long time to select the necessary ingredients.

As a result, after much effort, a sequence of actions was developed, all components were selected that give, if not 100%, then 95% of a good result. And most importantly, the process is so simple that the child can make the board completely independently. This is the method we will use. (of course, you can continue to bring it to the ideal - if you do better, then write). The advantages of this method:

all reagents are inexpensive, accessible and safe

no additional tools needed (irons, lamps, laminators - nothing, although not - you need a saucepan)

there is no way to damage the board - the board does not heat up at all

the paper comes off on its own - you can see the result of the toner transfer - where the transfer did not come out

there are no pores in the toner (they are sealed with paper) - therefore, there are no mordants

we do 1-2-3-4-5 and we always get the same result - almost 100% repeatability

Before we start, let's see what boards we need and what we can do at home using this method.

Basic requirements for manufactured boards

We will make devices on microcontrollers, using modern sensors and microcircuits. Microchips are getting smaller and smaller. Accordingly, the following requirements for boards must be met:

the boards must be double-sided (as a rule, it is very difficult to wire a single-sided board, making four-layer boards at home is quite difficult, microcontrollers need a ground layer to protect against interference)

the tracks should be 0.2mm thick - this size is quite enough - 0.1mm would be even better - but there is a possibility of etching and the tracks coming off during soldering

the gaps between tracks are 0.2mm - this is enough for almost all circuits. Reducing the gap to 0.1mm is fraught with merging of tracks and difficulty in monitoring the board for short circuits.

We will not use protective masks, nor will we do silk-screen printing - this will complicate production, and if you are making the board for yourself, then there is no need for this. Again, there is a lot of information on this topic on the Internet, and if you wish, you can do the “marathon” yourself.

We will not tin the boards, this is also not necessary (unless you are making a device for 100 years). For protection we will use varnish. Our main goal is to quickly, efficiently, and cheaply make a board for the device at home.

This is what the finished board looks like. made by our method - tracks 0.25 and 0.3, distances 0.2

How to make a double-sided board from 2 single-sided ones

One of the challenges of making double-sided boards is aligning the sides so that the vias line up. Usually a “sandwich” is made for this. Two sides are printed on a sheet of paper at once. The sheet is folded in half, and the sides are accurately aligned using special marks. Double-sided textolite is placed inside. With the LUT method, such a sandwich is ironed and a double-sided board is obtained.

However, with the cold toner transfer method, the transfer itself is carried out using a liquid. And therefore it is very difficult to organize the process of wetting one side at the same time as the other side. This, of course, can also be done, but with the help of a special device - a mini press (vice). Thick sheets of paper are taken - which absorb the liquid to transfer toner. The sheets are wetted so that the liquid does not drip and the sheet holds its shape. And then a “sandwich” is made - a moistened sheet, a sheet of toilet paper to absorb excess liquid, a sheet with a picture, a double-sided board, a sheet with a picture, a sheet of toilet paper, a moistened sheet again. All this is clamped vertically in a vice. But we won’t do that, we’ll do it simpler.

A very good idea came up on board manufacturing forums - what a problem it is to make a double-sided board - take a knife and cut the PCB in half. Since fiberglass is a layered material, this is not difficult to do with a certain skill:

As a result, from one double-sided board 1.5 mm thick we get two single-sided halves.

Next we make two boards, drill them and that’s it - they are perfectly aligned. It was not always possible to cut the PCB evenly, and in the end the idea came to use a thin one-sided PCB with a thickness of 0.8 mm. The two halves do not need to be glued together; they will be held together by soldered jumpers in the vias, buttons, and connectors. But if necessary, you can glue it with epoxy glue without any problems.

The main advantages of this hike:

Textolite with a thickness of 0.8 mm is easy to cut with paper scissors! In any shape, that is, it is very easy to cut to fit the body.

Thin PCB - transparent - by shining a flashlight from below you can easily check the correctness of all tracks, short circuits, breaks.

Soldering one side is easier - the components on the other side do not interfere and you can easily control the soldering of the microcircuit pins - you can connect the sides at the very end

You need to drill twice as many holes and the holes may slightly mismatch

The rigidity of the structure is slightly lost if you do not glue the boards together, but gluing is not very convenient

Single-sided fiberglass laminate with a thickness of 0.8mm is difficult to buy; most people sell 1.5mm, but if you can’t get it, you can cut thicker textolite with a knife.

Let's move on to the details.

Necessary tools and chemistry

We will need the following ingredients:

Now that we have all this, let’s take it step by step.

1. Layout of board layers on a sheet of paper for printing using InkScape

Automatic collet set:

We recommend the first option - it is cheaper. Next, you need to solder wires and a switch (preferably a button) to the motor. It is better to place the button on the body to make it more convenient to quickly turn the motor on and off. All that remains is to choose a power supply, you can take any power supply with 7-12V current 1A (less is possible), if there is no such power supply, then USB charging at 1-2A or a Krona battery may be suitable (you just have to try it - not everyone likes charging motors, the motor may not start).

The drill is ready, you can drill. But you just need to drill strictly at an angle of 90 degrees. You can build a mini machine - there are various schemes on the Internet:

But there is a simpler solution.

Drilling jig

To drill exactly 90 degrees, it is enough to make a drilling jig. We will do something like this:

It is very easy to make. Take a square of any plastic. We place our drill on a table or other flat surface. And drill a hole in the plastic using the required drill. It is important to ensure an even horizontal movement of the drill. You can lean the motor against the wall or rail and the plastic too. Next, use a large drill to drill a hole for the collet. From the reverse side, drill out or cut off a piece of plastic so that the drill is visible. You can glue a non-slip surface to the bottom - paper or rubber band. Such a jig must be made for each drill. This will ensure perfectly accurate drilling!

This option is also suitable, cut off part of the plastic on top and cut off a corner from the bottom.

Here's how to drill with it:

We clamp the drill so that it sticks out 2-3mm when the collet is fully immersed. We put the drill in the place where we need to drill (when etching the board, we will have a mark where to drill in the form of a mini hole in the copper - in Kicad we specially put a checkmark for this, so that the drill will stand there on its own), press the jig and turn on the motor - hole ready. For illumination, you can use a flashlight by placing it on the table.

As we wrote earlier, you can only drill holes on one side - where the tracks fit - the second half can be drilled without a jig along the first guide hole. This saves a little effort.

8. Tinning the board

Why tin the boards - mainly to protect copper from corrosion. The main disadvantage of tinning is overheating of the board and possible damage to the tracks. If you don’t have a soldering station, definitely don’t tin the board! If it is, then the risk is minimal.

You can tin a board with ROSE alloy in boiling water, but it is expensive and difficult to obtain. It is better to tin with ordinary solder. To do this efficiently, you need to make a simple device with a very thin layer. We take a piece of braid for desoldering parts and put it on the tip, screw it to the tip with wire so that it does not come off:

We cover the board with flux - for example LTI120 and the braid too. Now we put tin into the braid and move it along the board (paint it) - we get an excellent result. But as you use the braid, it comes apart and copper fluff begins to remain on the board - they must be removed, otherwise there will be a short circuit! You can see this very easily by shining a flashlight on the back of the board. With this method, it is good to use either a powerful soldering iron (60 watt) or ROSE alloy.

As a result, it is better not to tin the boards, but to varnish them at the very end - for example, PLASTIC 70, or simple acrylic varnish purchased from auto parts KU-9004:

Fine tuning of the toner transfer method

There are two points in the method that can be tuned and may not work right away. To configure them, you need to make a test board in Kicad, tracks in a square spiral of different thicknesses, from 0.3 to 0.1 mm and with different intervals, from 0.3 to 0.1 mm. It is better to immediately print several such samples on one sheet and make adjustments.

Possible problems that we will fix:

1) tracks can change geometry - spread out, become wider, usually very little, up to 0.1mm - but this is not good

2) the toner may not stick well to the board, come off when the paper is removed, or stick poorly to the board

The first and second problems are interconnected. I solve the first one, you come to the second one. We need to find a compromise.

The tracks can spread for two reasons - too much pressure, too much acetone in the resulting liquid. First of all, you need to try to reduce the load. The minimum load is about 800g, it is not worth reducing below. Accordingly, we place the load without any pressure - we just put it on top and that’s it. There must be 2-3 layers of toilet paper to ensure good absorption of excess solution. You must ensure that after removing the weight, the paper should be white, without purple smudges. Such smudges indicate severe melting of the toner. If you can’t adjust it with a weight and the tracks still blur, then increase the proportion of nail polish remover in the solution. You can increase to 3 parts liquid and 1 part acetone.

The second problem, if there is no violation of the geometry, indicates insufficient weight of the load or a small amount of acetone. Again, it’s worth starting with the load. More than 3 kg does not make sense. If the toner still does not stick well to the board, then you need to increase the amount of acetone.

This problem mainly occurs when you change your nail polish remover. Unfortunately, this is not a permanent or pure component, but it was not possible to replace it with another. I tried to replace it with alcohol, but apparently the mixture is not homogeneous and the toner sticks in some patches. Also, nail polish remover may contain acetone, then less of it will be needed. In general, you will need to carry out such tuning once until the liquid runs out.

The board is ready

If you do not immediately solder the board, it must be protected. The easiest way to do this is to coat it with alcohol rosin flux. Before soldering, this coating will need to be removed, for example, with isopropyl alcohol.

Alternative options

You can also make a board:

Additionally, custom board manufacturing services are now gaining popularity - for example Easy EDA. If you need a more complex board (for example, a 4-layer board), then this is the only way out.

A printed circuit board is a dielectric plate on the surface of which conductive tracks are applied and places are prepared for mounting electronic components. Electrical radio components are usually installed on the board using soldering.

PCB device

The electrically conductive tracks of the board are made of foil. The thickness of the conductors is, as a rule, 18 or 35 microns, less often 70, 105, 140 microns. The board has holes and contact pads for mounting radio elements.

Separate holes are used to connect conductors located on different sides of the board. A special protective coating and markings are applied to the outer sides of the board.

Stages of creating a printed circuit board

In amateur radio practice, we often have to deal with the development, creation and manufacture of various electronic devices. Moreover, any device can be built on a printed circuit board or a regular board with surface mounting. The PCB works much better, is more reliable and looks more attractive. Creating it involves performing a number of operations:

Preparation of the layout;

Drawing on textolite;

Etching;

Tinning;

Installation of radio elements.

Manufacturing printed circuit boards is a complex, labor-intensive, and interesting process.

Development and production of a layout

The board drawing can be done manually or on a computer using one of the special programs.

It is best to draw the board manually on recorder paper on a 1:1 scale. Graph paper is also suitable. Installed electronic components must be displayed in mirror image. The tracks on one side of the board are shown as solid lines, and on the other side as dotted lines. The dots mark the places where radio elements are attached. Soldering areas are drawn around these places. All drawings are usually made using a drawing board. As a rule, simple drawings are made by hand; more complex printed circuit board designs are developed on a computer in special applications.

Most often they use a simple program called Sprint Layout. Only a laser printer is suitable for printing. The paper should be glossy. The main thing is that the toner does not eat into it, but remains on top. The printer must be adjusted so that the toner thickness of the drawing is maximum.

Industrial production of printed circuit boards begins with entering the circuit diagram of the device into a computer-aided design system, which creates a drawing of the future board.

Preparing the workpiece and drilling holes

First of all, you need to cut a piece of PCB with the given dimensions. File the edges. Attach the drawing to the board. Prepare the tool for drilling. Drill directly according to the drawing. The drill bit must be of good quality and match the diameter of the smallest hole. If possible, you should use a drilling machine.

Having made all the necessary holes, remove the drawing and drill out each hole to the specified diameter. Clean the surface of the board with fine sandpaper. This is necessary to eliminate burrs and improve paint adhesion to the board. To remove traces of grease, treat the board with alcohol.

Drawing on fiberglass laminate

The board drawing can be applied to the PCB manually or using one of many technologies. Laser ironing technology is the most popular.

Manual drawing begins by marking the mounting areas around the holes. They are applied using a drawing pen or a match. The holes are connected with tracks in accordance with the drawing. It is better to draw with nitro paint in which rosin is dissolved. This solution provides strong adhesion to the board and good resistance to high-temperature etching. Asphalt bitumen varnish can be used as paint.

Manufacturing printed circuit boards using laser-iron technology gives good results. It is important to perform all operations correctly and carefully. The degreased board must be placed on a flat surface with the copper facing up. Carefully place the design on top with the toner facing down. Additionally, add a few more sheets of paper. Iron the resulting structure with a hot iron for about 30-40 seconds. When exposed to temperature, the toner should change from a solid to a viscous state, but not to a liquid. Let the board cool and place it in warm water for a few minutes.

The paper will become limp and tear off easily. You should carefully examine the resulting drawing. The absence of separate tracks indicates that the iron temperature is insufficient; wide tracks are obtained when the iron is too hot or the board is heated for an excessively long time.

Small defects can be corrected with a marker, paint or nail polish. If you don’t like the workpiece, then you need to wash everything off with a solvent, clean it with sandpaper and repeat the process again.

Etching

A grease-free printed circuit board is placed in a plastic container with the solution. At home, ferric chloride is usually used as a solution. The bath with it needs to be rocked periodically. After 25-30 minutes, the copper will completely dissolve. Etching can be accelerated by using a heated ferric chloride solution. At the end of the process, the printed circuit board is removed from the bath and thoroughly washed with water. Then the paint is removed from the conductive paths.

Tinning

There are many methods of tinning. We have a prepared printed circuit board. At home, as a rule, there are no special devices and alloys. Therefore, they use a simple, reliable method. The board is coated with flux and tinned with a soldering iron with regular solder using copper braiding.

Installation of radio elements

At the final stage, the radio components are inserted one by one into the places intended for them and soldered. Before soldering, the legs of the parts must be treated with flux and, if necessary, shortened.

The soldering iron should be used carefully: if there is excess heat, the copper foil may begin to peel off and the printed circuit board will be damaged. Remove any remaining rosin with alcohol or acetone. The finished board can be varnished.

Industrial development

It is impossible to design and manufacture a printed circuit board for high-end equipment at home. For example, the printed circuit board of an amplifier for High-End equipment is multi-layered, copper conductors are coated with gold and palladium, conductive tracks have different thicknesses, etc. Achieving this level of technology is not easy even in an industrial enterprise. Therefore, in some cases, it is advisable to purchase a ready-made high-quality board or place an order to carry out work according to your own scheme. Currently, the production of printed circuit boards is established at many domestic enterprises and abroad.