How to make a solution for etching printed circuit boards. PCB etching

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Amateur radio technology for manufacturing printed circuit boards at home consists of several stages.

Drawing.

Etching solution.

Etching.

Drawing using a laser printer.

Preparation of printed circuit board drawings.

It is most convenient to carry out the drawing manually printed circuit board on a scale of 1:1 on recorder paper (has a square with a side of 2.5 mm, in the “pitch” of the microcircuits), if there is none, then you can “xerify” the school paper “into the square” with a 2-fold reduction, in the most extreme case you can use regular graph paper. The tracks on the solder side should be drawn with solid lines, and the tracks on the parts side (in the case of double-sided installation) should be drawn with dotted lines. It should be noted that the elements placed must be in mirror image. The centers of the element legs are marked with points around which it is necessary to draw a solder pad. For subsequent actions, it is very important what size you choose the mounting pads for the elements (it’s a shame when, when drawing a board “live”, either the path between the pads does not go through, or after soldering the elements fall out along with the pads). The width of the tracks should be chosen based on what you will use to draw the board, when using glass drawing boards of approximately 1.5 mm. After the drawing is ready, you need to attach the drawing to a luminous surface (for example, window glass) reverse side towards you and circle the dotted lines. This way you will get a drawing from the installation side of the parts. Next, you need to cut out a drawing of a sheet of paper, but taking into account the “wings” for fastening on each side (about 15 mm).

Preparation of fiberglass laminate and drilling.

Cut a piece of fiberglass to the size of the drawing. Remove burrs with a file. Place the design on the board, fold the edges of the paper and secure them to the back with tape or (preferably) electrical tape. Next is the drilling process. Yes, yes, right according to the drawing and without punching. An important condition What prevents the drill from misleading is its “freshness.” However, you can understand what to expect from a specific drill by drilling a test hole on some scrap of fiberglass. The best decision this problem - the presence of an appropriate drilling machine, even if it’s homemade. If a “motor with a drill” is used, as a rule, it is better to “punch” future holes. All holes, including mounting ones, are drilled with the same (smallest) diameter. Next, you need to check the drilling for “clearance” as there will definitely be undrilled holes. Drill more. After this, the board drawing is very carefully removed from the fiberglass (the danger is burrs from drilling). Next, the mounting and other large-diameter holes are drilled out.

After the operations have been completed, the surface of the board is cleaned with fine sandpaper. This process is necessary to remove burrs from drilling and for better adhesion of the design paint to the surface. If possible, do not touch the cleaned surface with your fingers to avoid leaving grease marks. After cleaning, it is necessary to degrease the board using alcohol (in extreme cases, acetone, but make sure that no white powdery stains remain). After this, you can only touch the end surfaces with your fingers.

Drawing.

In our circles, of course, we argued a lot about the paint used and the technology for applying the paths, but I settled on what is described below. Drawing is done with nitro paint, with rosin powder dissolved in it (provides plasticity for correction for some time after drying and does not allow the paint to “lag behind” in the case of etching with hot solutions). Drawing is done with glass drawing pens (which are very difficult to find these days). In addition, it is possible to use as a paint, asphalt-bitumen varnish, dissolved to the desired condition with xylene. The bottle will last a very long time. It is possible to make drawing feeders yourself, with appropriate training, of course. To do this, you can take a thin-walled glass tube and stretch it on the flame (over gas stove) break it in the middle. Then “finish” the broken tip on fine sandpaper. Next, after heating over the same flame, bend the tip until desired angle. Difficult!? In fact, no more than 5 minutes. You can also use disposable syringes for drawing. The varnish is drawn into a disposable syringe (1-2 ml) and a thin needle is inserted. Before installation, the needle must be processed with a file so that the edges are smooth (remove the sharp end). From the side of the piston, you can insert another needle to allow air to pass inside the syringe.

Before you start drawing the printed circuit tracks, you need to draw the mounting pads for soldering the elements. They are applied using a glass pen or a sharpened match around each hole, approximately 3 mm in diameter. Next you need to let them dry. After this, you need to cut them using a compass until required diameter(I use a small compass-measuring device with a threaded distance clamp (may professional draftsmen forgive me this expression, I never knew its real name), one of the needles of which is turned into a flat cutter). Next, the trimmed excess is cleaned with an awl or scalpel. In fact, I use a recycled school utensil for these procedures. The result is smooth round areas of the same diameter, which can only be connected by tracks, according to the previously drawn drawing of the printed circuit board. Next, after drying, the second side is drawn. Then the tracks and errors are corrected using a scalpel. Moreover, it should be noted that in order to align the edge of the track, you must first trim the edge using a ruler (preferably a metal one), and then remove the excess by scratching. If you clean the path right away, then depending on the degree of dryness of the paint, you can get “chips” even worse than the original ones. Check that the pattern on the board matches the pattern on the drawing.

Production of etching substance.

There are various compositions for etching, foil material in the manufacture of printed circuit boards.

Recipe No. 1.

For forced (4-6 min) etching, you can use the following composition (in mass parts): 38% hydrochloric acid with a density of 1.19 g/cm 3, 30% hydrogen peroxide (peroxide)-perhydrol. If hydrogen peroxide has a concentration of 16-18%, then for 20 parts by weight of acid take 40 parts of peroxide and the same amount of water. First, peroxide is mixed with water, and then acid is added. Printed conductors and contact pads should be protected with acid-resistant paint, for example nitro enamel NTs-11.

Recipe No. 2.

In glass cold water dissolve 4-6 tablets of hydrogen peroxide and carefully add 15-25 ml of concentrated sulfuric acid. To apply a printed circuit board design to foil material, you can use BF-2 glue. The etching time in this solution is approximately 1 hour.

Recipe No. 3.

In 500 ml of hot (approximately 80 ° C) water, dissolve four tablespoons of table salt and two tablespoons of copper sulfate crushed into powder. The solution becomes dark green in color. Ready for use immediately after cooling (not necessary for heat-resistant paint, see above). The solution is enough to remove 200 cm 3 of foil. Etching time is about 8 hours. If the printed circuit board design is made with sufficiently heat-resistant paint or varnish, the solution temperature can be raised to approximately 50 ° C, and then the etching intensity will increase.

Recipe No. 4.

Dissolve 350 g of chromic anhydride in 1 liter of hot water (60-70 °C), then add 50 g of table salt *. After the solution has cooled, begin etching. Etching time 20-60 min. If you add 50 g of concentrated sulfuric acid to the solution, the etching will be more intense.

Recipe No. 5.

Dissolve 150 g of ferric chloride powder in 200 ml of warm water.

Preparation of ferric chloride.

If there is no ready-made ferric chloride (in powder), then you can prepare it yourself. To do this you need to have 9% hydrochloric acid and fine iron filings. For 25 parts by volume of acid, take one part of iron filings. The sawdust is poured into an open vessel with acid and left for several days. At the end of the reaction, the solution becomes light green, and after 5-6 days the color changes to yellow-brown - the ferric chloride solution is ready for use. To prepare ferric chloride, you can use powdered red lead. In this case, for one volume part of concentrated hydrochloric acid, 1.5-2 parts of red lead are required. The components are mixed in a glass container, adding red lead in small portions. After termination chemical reaction A precipitate and a solution of ferric chloride fall to the bottom. Ready to use

Etching and processing of the board.

Etching should be done in plastic (photo cuvette) or porcelain (plate) dishes. If the fee Not large sizes, it is convenient to poison it in a plate. A deep plate is selected so that the board does not lie completely on the bottom, but rests with its corners on the walls of the plate. Then between the board and the bottom there will be a space filled with solution. During etching, the board must be turned over and the solution stirred. If you need to quickly etch the board, heat the solution to 50-70 degrees. If the board is large, then insert matches into the mounting holes (in the corners) so that they protrude 5-10 mm on both sides. You can insert copper wire, but then the solution will be more saturated with copper. Etch in a photo cuvette, stirring and turning the board over. When working with ferric chloride solution, you must be careful. The solution is almost impossible to wash off from clothes and objects. In case of contact with skin, wash with soda solution. The porcelain plate is easily washed from the solution and can be used further for its intended purpose. After etching is complete, drain the solution into plastic bottle, you will still need it. Rinse the board in cold running water. Under a thin stream of water, remove the varnish using a safety blade (scrape). The dried board must be cleaned with a scalpel to remove excess connections and spilled varnish. If the tracks are close to each other, then you can expand the lumen with a scalpel. After this, the board is processed again with fine sandpaper.

Tinning the board.

There is no need to write about the usefulness of this procedure. Otherwise, you can stop at the previous one. Next, the surfaces of the board are covered with a brush with liquid rosin flux. Tinning is carried out using tinned screen braid, cleared of wires ( white). The braid is first impregnated with rosin and a small amount of solder (you can, of course, also use Rose alloy, but this is already exotic). Next, the braid is pressed to the surface of the track with a soldering iron and slowly evenly (selected experimentally) along the length of the track. If all conditions are met correctly, the result will be a smooth white tinned path. After all the tracks on all sides have been processed, the board is washed with alcohol. Washing with acetone is undesirable, since solder with acetone gives over time a conductive chemical compound in the form white plaque along the edges of platforms and tracks, and with sufficient installation density there is a danger of unnecessary galvanic connections. After washing, holes are drilled (cleaned) for installing r/components.

The board is ready for installation.

Printed circuit boards using a laser printer.

The method of manufacturing single printed circuit boards by transferring a design from a printout on a laser printer is becoming increasingly popular among radio amateurs. It is best to print on thin coated paper - it has less lint, good results are obtained on sheets of the "Stereo & Video" magazine, as well as "self-adhesive" substrates and thermal paper for faxes (choose the side experimentally). In laser printers, you should enable the maximum toner supply mode (turn off the "economy" mode if it was turned on, set the contrast to maximum, etc.), and also use a path with minimal paper bending (this option is available in older HP LJ 2 models , LJ4, etc.). The board design must be “mirrored”; this option is available in the print menu of many graphics programs, for example Corel Draw, Corel Photo Paint, and when printing from programs that cannot “mirror”, it is necessary to use output to Postscript printers that have a mirroring option in the driver. Instead of outputting to a laser printer, you can use photocopying, but also in maximum contrast mode and on thermal fax paper. When making two-layer printed circuit boards, in order to reduce the heat shrinkage of the paper, it is recommended to “run” the latter through the printer empty (without printing the image) before printing the image. In addition, both sides should be on the same sheet to avoid severe misalignment due to different heat shrinkage of the paper. The degreased board is laid with the copper side up on a flat surface, with the resulting print on top, toner side down. This “sandwich” is pressed on the paper side with an iron (for 20 - 30 seconds), heated to the ironing temperature of crepe de Chine (ask the ladies). The iron should not immediately melt the image made by the laser printer. That is, the toner at this temperature should turn from solid to viscous, but not liquid. When the board has cooled down, you need to immerse it in warm water and hold it there for several minutes. As soon as the paper becomes limp (it will be visible), everything can be easily pulled off, the rest can simply be rolled up with your finger. Instead of water, you can remove the paper with sulfuric acid. If the tracks are greased, you carelessly removed the iron or placed a cold weight. If the tracks are missing somewhere, the iron is too cold. If the tracks become wide, the iron is too hot, or the board was heated for too long. If the board is double-sided, then first the paper printouts of both sides are aligned to the light, two technological holes are pierced in any free opposite places with a needle, the first side of the board is “ironed” as usual, then it is drilled along the technological holes with a thin drill, and on the other side along them the gap is aligned with the paper printout of the other side. You can poison with ferric chloride (warm it up a little to speed it up) or with hodgepodge with hydropyrite. All this was used even on getinax, there are no peelings of the tracks, tracks up to 0.8 mm wide are normally made, and with some experience up to 0.5 mm. After etching, the toner is removed with acetone, nail polish remover or Flux Off spray. Drilled, trimmed and so on, as usual...

Another way to apply a design to paper using a laser printer.

Making printed material using a laser printer and an iron is a rather tedious process, but it gives a pretty good result if you practice a little.

1 . Carefully glue a sheet of fax paper (glossy side up) onto a sheet of regular paper (to compensate for the lack of faxing rigidity). For what? It is necessary to first run the paper through the printer/laser oven for shrinkage. To smoothly pull through the tract, simply iron the thermal paper on the sensitive side with an iron.
2 . Paper - take the base from self-adhesive paper, or thermal paper for faxing, definitely thermal paper, and prepared - first iron the sheets with a hot iron until flat (at the same time they will turn dark brown, then bluish-gray), fold them in this form for future use. Before outputting the board, run the sheet through the printer - for example, by printing a blank page. The minimum sheet size is ~6*12 cm for HP 5/6L.
3 . Print at maximum boldness, mirror image. printing and transferring to the blank can be up to a week apart, I haven’t tried it again (this is for those who don’t have a laser at home).
4 . Take the workpiece with a margin of 3-5 mm on each side. Lightly sand the foil with zero polish and wipe. There should not be any harmful deposits such as white sediment from denatured alcohol. I use isopropyl alcohol or gasoline "galosh" (aka "for lighters").
5 . Iron - with a normal, smooth surface. reheat in advance. Temperature - for waxing you need to select it more carefully (I have a display meter set to "artificial silk"), otherwise the impregnation will begin to transfer. for thermal paper - higher is possible.
6 . There shouldn’t be any dust or any small things, either on the foil or on the paper.
7 . Make a sandwich - on a flat thick plywood (although I have 3 mm paper), put a piece of thick cardboard, a blank board, blow off the dust, drawing, for thermal paper (it's thin) - also a piece of moderately thick paper, a hot iron.
8 . You begin to move with the iron, pressing with a force of ~5..10 kg/sq.dm. wait about two minutes for it to stick.
9 . Tilting the iron very slightly, you roll out individual tracks for a couple of minutes. It is very important here not to crush the tracks, and at the same time to weld them. From time to time you need to lower the iron to the entire plane so that the rest of the iron does not cool down. The thermal paper clearly shows the difference in welded and defective pieces.
10 . Well, you iron for another minute to clear your conscience and put the iron away. The sandwich cools and sections of paper between the tracks swell. We don’t wait for it to cool down, put the board directly under a stream of boiling water.
11 . Now the board - under running water and a piece of wet foam rubber, you begin to erase the paper. You cannot tear it off in large pieces or from dry foil. You need to remove clumps of paper from the foam rubber more often. We take the paper by the corner and tear it off. Then remove the remains with your finger/rag/foam rubber.
12 . Use a new piece of sponge to wipe off the lint (as much as possible), and look at the wet pattern under a magnifying glass. if there are many defects, or they are located in inconvenient places - see point 1, with variations in parameters.
13 . Cover the reverse side with strips of wide tape and etch. It is possible even in boiling FeCl3

Method of applying a drawing to a paper using a laser printer

I make everything much simpler:
I take the blank and a simple Soviet eraser. I thoroughly wipe the entire board with an eraser. All oxidation is removed. Just in case, you can wipe it with gasoline (but I don’t do this, an eraser is enough). Then I take the thermal paper from the fax machine and iron it with an iron. It turns gray-violet. I insert this paper into the printer (I have an HP 6L and I don’t glue any paper for rigidity, I haven’t chewed it yet) and mirror print the board design. I put the paper on the paper and start fiddling with the iron. My power is at 3/4 of the maximum power. I iron for 3-4 minutes. Then I throw the workpiece into hot, warm water and wait 5 minutes for the paper to soften. Then I use a sponge or fingers to roll the paper off the board. Do not pick up the edge of the paper or tear it off; the tracks may come off along with the paper! Just roll it off the board. Next - core, drill, trim and etching. And the board is ready.

conditions using hydrogen peroxide. Everything is very simple and does not require much effort.

To work we will need the following list of tools:
- Program - layout 6.0.exe (other modification is possible)
- Negative photoresist (this is a special film)
- Laser printer
- Transparent film for printing
- Marker for printed circuit boards (if not, you can use nitro polish or nail polish)
- Foil PCB
- UV lamp (if there is no lamp, wait for sunny weather and use the sun’s rays, I’ve done this many times and everything works out)
- Two pieces of plexiglass (you can do one, but I made two for myself), you can also use a CD box
- Stationery knife
- Hydrogen peroxide 100 ml
- Lemon acid
- Soda
- Salt
- Level hands (this is a must)

In the layout program we do the board layout

We check it carefully so as not to confuse anything and print it

Be sure to check all the boxes on the left as shown in the photo. The photo shows that our drawing is in a negative image, since our photoresist is negative, those areas that are hit by UV rays will be tracks, and the rest will be washed off, but more on that a little later.

Next, we take a transparent film for printing on a laser printer (available for free sale), one side is slightly matte and the other is glossy, and so we place the film so that the design is on the matte side.

We take the PCB and cut it to the size of the required board

Cut the photoresist to size (when working with photoresist, avoid direct sunlight, as it will damage the photoresist)

We clean the PCB with an eraser and wipe it so that there is no debris left

Next, we tear off the protective transparent film on the photoresist.

And carefully glue it to the PCB, it is important that there are no bubbles. Iron it well so that everything sticks well.

Next we need two pieces of plexiglass and two clothespins, you can use a CD box

We place our printed template on the board, be sure to place the template with the printed side on the PCB and clamp it between the two halves of plexiglass so that everything fits tightly

Afterwards we will need a UV lamp (or a simple sun on a sunny day)

We screw the light bulb into any lamp and place it above our board at a height of about 10-20 cm. And turn it on, the illumination time from such a lamp as in the photo at a height of 15 cm for me is 2.5 minutes. I don’t recommend it for longer, you might ruin the photoresist

After 2 minutes, turn off the lamp and see what happens. Paths must be clearly visible

If everything is clearly visible, proceed to the next step.

Take the listed ingredients
- Peroxide
- Lemon acid
- Salt
- Soda

Now we need to remove unexposed photoresist from the board; it needs to be removed in solution soda ash. If it doesn't exist, then you need to make it. Boil water in a kettle and pour it into a container

Pour plain soda into it. You don’t need much for 100-200 ml, 1-2 tablespoons of soda and mix well, a reaction should begin

Let the solution cool to 20-35 degrees (you can’t put the board directly into a hot solution, all the photoresist will peel off)
We take our payment and remove the second one protective film NECESSARILY

And put the board in the COOLED solution for 1-1.5 minutes

Periodically, we take out the board and wash it under running water, carefully cleaning it with your finger or a soft kitchen sponge. When all the excess is washed off, there should be a board like this left:

The photo shows that a little more was washed off than necessary, probably overexposed in the solution (which is not recommended)

But it's okay. just take a marker for printed circuit boards or nail polish and cover up all the mistakes with it

Next, pour 100 ml of peroxide, 3-4 tablespoons of citric acid and 2 tablespoons of salt into another container.

Printed circuit board– this is a dielectric base, on the surface and in the volume of which conductive paths are applied in accordance with electrical diagram. The printed circuit board is intended for mechanical fastening and electrical connection between the leads of electronic and electrical products installed on it by soldering.

The operations of cutting out a workpiece from fiberglass, drilling holes and etching a printed circuit board to obtain current-carrying tracks, regardless of the method of applying the pattern to the printed circuit board, are performed using the same technology.

Manual application technology
PCB tracks

Preparing the template

The paper on which the PCB layout is drawn is usually thin and for more accurate drilling of holes, especially when using manual homemade drill so that the drill does not lead to the side, it is necessary to make it more dense. To do this, you need to glue the printed circuit board design onto thicker paper or thin thick cardboard using any glue, such as PVA or Moment.

Cutting the workpiece

A blank of foil fiberglass laminate of a suitable size is selected, the printed circuit board template is applied to the blank and outlined around the perimeter with a marker, a soft pencil or marking with a sharp object.

Next, the fiberglass laminate is cut along the marked lines using metal scissors or sawed out with a hacksaw. Scissors cut faster and there is no dust. But we must take into account that when cutting with scissors, fiberglass is strongly bent, which somewhat worsens the adhesion strength of copper foil and if the elements need to be re-soldered, the tracks may peel off. Therefore, if the board is large and has very thin traces, then it is better to cut it using a hacksaw.

The template of the printed circuit board pattern is glued to the cut-out workpiece using Moment glue, four drops of which are applied to the corners of the workpiece.

Since the glue sets in just a few minutes, you can immediately begin drilling holes for radio components.

Drilling holes

It is best to drill holes using a special mini drilling machine with a carbide drill with a diameter of 0.7-0.8 mm. If a mini drilling machine is not available, then you can drill holes with a low-power drill using a simple drill. But when working with a universal hand drill, the number of broken drills will depend on the hardness of your hand. You definitely won’t be able to get by with just one drill.

If you cannot clamp the drill, you can wrap its shank with several layers of paper or one layer of sandpaper. You can wrap a thin metal wire tightly around the shank, turn to turn.

After finishing drilling, check whether all holes are drilled. This can be clearly seen if you look at the printed circuit board up to the light. As you can see, there are no missing holes.

Applying a topographic drawing

In order to protect the places of foil on fiberglass laminate that will be conductive paths from destruction during etching, they must be covered with a mask that is resistant to dissolution in an aqueous solution. For the convenience of drawing paths, it is better to pre-mark them using a soft pencil or marker.

Before applying the markings, it is necessary to remove traces of the glue that was used to glue the printed circuit board template. Since the glue has not hardened much, it can be easily removed by rolling it with your finger. The surface of the foil must also be degreased using a rag using any means, for example acetone or white alcohol (the so-called purified gasoline), or any detergent for washing dishes, for example Ferry.

After marking the tracks of the printed circuit board, you can begin to apply their design. Any waterproof enamel is well suited for drawing paths, for example alkyd enamel PF series, diluted to a suitable consistency with white alcohol solvent. You can draw paths different instruments– a glass or metal drawing pen, a medical needle and even a toothpick. In this article I will tell you how to draw circuit board traces using a drawing pen and ballerina, which are designed for drawing on paper with ink.

Previously, there were no computers and all drawings were drawn with simple pencils on whatman paper and then transferred in ink to tracing paper, from which copies were made using copiers.

Drawing begins with contact pads, which are drawn with a ballerina. To do this, you need to adjust the gap of the sliding jaws of the ballerina drawing board to the required line width and to set the diameter of the circle, perform the adjustment with the second screw, moving the drawing blade away from the axis of rotation.

Next, the ballerina's drawing board is filled with paint to a length of 5-10 mm using a brush. For applying a protective layer to a printed circuit board, PF or GF paint is best suited, since it dries slowly and allows you to work quietly. NTs brand paint can also be used, but it is difficult to work with because it dries quickly. The paint should adhere well and not spread. Before painting, the paint must be diluted to a liquid consistency, adding a suitable solvent to it little by little with vigorous stirring and trying to paint on scraps of fiberglass. To work with paint, it is most convenient to pour it into a bottle of manicure varnish, in the twist of which there is a solvent-resistant brush installed.

After adjusting the ballerina's drawing board and obtaining the required line parameters, you can begin to apply the contact pads. To do this, the sharp part of the axis is inserted into the hole and the base of the ballerina is rotated in a circle.

With the correct setting of the drawing pen and the desired consistency of paint around the holes on the printed circuit board, perfectly round circles are obtained. When a ballerina begins to paint poorly, the remaining dried paint is removed from the gap of the pen with a cloth and the pen is filled with fresh paint. To draw all the holes on this printed circuit board with circles it took only two refills of the drawing pen and no more than two minutes of time.

Once the round pads on the board are drawn, you can start drawing the conductive paths using a hand drawing pen. Preparing and adjusting a manual drawing board is no different from preparing a ballerina.

The only thing additionally needed is a flat ruler, with pieces of rubber 2.5-3 mm thick glued to one of its sides along the edges, so that the ruler does not slip during operation and the fiberglass, without touching the ruler, can freely pass under it. Best suited as a ruler wooden triangle, it is stable and at the same time can serve as a hand support when drawing a printed circuit board.

To prevent the printed circuit board from slipping when drawing tracks, it is advisable to place it on a sheet of sandpaper, which consists of two sandpaper sheets sealed together with the paper sides.

If they come into contact when drawing paths and circles, then you should not take any measures. You need to let the paint on the printed circuit board dry until it does not stain when touched, and use the tip of a knife to remove the excess part of the design. In order for the paint to dry faster, the board should be placed in a warm place, for example, on a radiator in winter. In the summer - under the rays of the sun.

When the design on the printed circuit board is completely applied and all defects are corrected, you can proceed to etching it.

Printed circuit board design technology
using a laser printer

When printing on a laser printer, the image formed by the toner is transferred, due to electrostatics, from the photo drum on which the laser beam drew the image, onto paper. The toner is held onto the paper, preserving the image, only due to electrostatics. To fix the toner, the paper is rolled between rollers, one of which is a thermal oven heated to a temperature of 180-220°C. The toner melts and penetrates the paper texture. Once cooled, the toner hardens and adheres firmly to the paper. If the paper is heated again to 180-220°C, the toner will again become liquid. This property of toner is used to transfer images of current-carrying tracks onto a printed circuit board at home.

After the file with the printed circuit board design is ready, you need to print it using a laser printer onto paper. Please note that the image of the printed circuit board drawing for this technology must be viewed from the side where the parts are installed! An inkjet printer is not suitable for these purposes, as it works on a different principle.

Preparing a paper template for transferring the design to the printed circuit board

If you print a printed circuit board design on ordinary paper for office equipment, then due to its porous structure, the toner will penetrate deeply into the body of the paper and when the toner is transferred to the printed circuit board, most of it will remain in the paper. In addition, there will be difficulties in removing paper from the printed circuit board. You will have to soak it in water for a long time. Therefore, to prepare a photomask, you need paper that does not have a porous structure, for example photo paper, a substrate from self-adhesive films and labels, tracing paper, pages from glossy magazines.

I use old stock tracing paper as the paper for printing the PCB design. Tracing paper is very thin and it is impossible to print a template directly on it; it gets jammed in the printer. To solve this problem, before printing, you need to apply a drop of any glue to a piece of tracing paper of the required size in the corners and glue it to a sheet of A4 office paper.

This technique allows you to print a printed circuit board design even on the thinnest paper or film. In order for the toner thickness of the drawing to be maximum, before printing, you need to configure the “Printer Properties” by turning off the economical printing mode, and if this function is not available, then select the coarsest type of paper, for example cardboard or something similar. It is quite possible that you will not get a good print the first time, and you will have to experiment a little, choosing best mode laser printer printing. In the resulting print of the design, the tracks and contact pads of the printed circuit board must be dense without gaps or smudging, since retouching at this technological stage is useless.

All that remains is to cut the tracing paper along the contour and the template for making the printed circuit board will be ready and you can proceed to the next step, transferring the image onto fiberglass laminate.

Transferring a design from paper to fiberglass

Transferring the printed circuit board design is the most critical step. The essence of the technology is simple: paper, with the side of the printed pattern of the tracks of the printed circuit board, is applied to the copper foil of fiberglass and pressed with great force. Next, this sandwich is heated to a temperature of 180-220°C and then cooled to room temperature. The paper is torn off, and the design remains on the printed circuit board.

Some craftsmen suggest transferring a design from paper to a printed circuit board using an electric iron. I tried this method, but the result was unstable. It is difficult to simultaneously heat the toner to desired temperature and uniform pressing of the paper to the entire surface of the printed circuit board when the toner hardens. As a result, the pattern is not completely transferred and gaps remain in the pattern of the printed circuit board tracks. Perhaps the iron was not heating up enough, although the regulator was set to maximum iron heating. I didn’t want to open the iron and reconfigure the thermostat. Therefore, I used another technology, less labor-intensive and providing one hundred percent results.

On a piece of foil fiberglass laminate cut to the size of the printed circuit board and degreased with acetone, I glued tracing paper with a pattern printed on it in the corners. On top of the tracing paper I placed, for more even pressure, heels of sheets of office paper. The resulting package was placed on a sheet of plywood and covered on top with a sheet of the same size. This entire sandwich was clamped with maximum force in clamps.

All that remains is to heat the prepared sandwich to a temperature of 200°C and cool. An electric oven with a temperature controller is ideal for heating. It is enough to place the created structure in a cabinet, wait for the set temperature to reach, and after half an hour remove the board to cool.

If you don’t have an electric oven, you can also use a gas oven by adjusting the temperature using the gas supply knob using the built-in thermometer. If there is no thermometer or it is faulty, then women can help; the position of the control knob at which pies are baked is suitable.

Since the ends of the plywood were warped, I clamped them with additional clamps just in case. To avoid this phenomenon, it is better to clamp the printed circuit board between metal sheets 5-6 mm thick. You can drill holes in their corners and clamp printed circuit boards, tighten the plates using screws and nuts. M10 will be enough.

After half an hour, the structure has cooled enough for the toner to harden, and the board can be removed. At the first glance at the removed printed circuit board, it becomes clear that the toner transferred from tracing paper to the board perfectly. The tracing paper fit tightly and evenly along the lines of the printed tracks, rings of contact pads and marking letters.

The tracing paper easily came off from almost all the traces of the printed circuit board; the remains of the tracing paper were removed using damp cloth. But still, there were gaps in several places on the printed tracks. This can happen as a result of uneven printing from the printer or remaining dirt or corrosion on the fiberglass foil. Gaps can be painted over with any waterproof paint, manicure polish, or retouched with a marker.

To check the suitability of a marker for retouching a printed circuit board, you need to draw lines on paper with it and moisten the paper with water. If the lines do not blur, then the retouching marker is suitable.

It is best to etch a printed circuit board at home in a solution of ferric chloride or hydrogen peroxide with citric acid. After etching, toner can be easily removed from the printed tracks with a swab soaked in acetone.

Then holes are drilled, conductive paths and contact pads are tinned, and radioelements are sealed.

This is the appearance of the printed circuit board with radio components installed on it. The result was a power supply and switching unit for electronic system, complementing an ordinary toilet with a bidet function.

PCB etching

To remove copper foil from unprotected areas of foiled fiberglass laminate when making printed circuit boards at home, radio amateurs usually use chemical method. The printed circuit board is placed in an etching solution and, due to a chemical reaction, the copper unprotected by the mask dissolves.

Recipes for pickling solutions

Depending on the availability of components, radio amateurs use one of the solutions given in the table below. Etching solutions are arranged in order of popularity of their use by radio amateurs at home.

Name of solution	Compound	Quantity	Cooking technology	Advantages	Flaws
Hydrogen peroxide plus citric acid	Hydrogen peroxide (H 2 O 2)	100 ml	Dissolve citric acid and table salt in a 3% solution of hydrogen peroxide.	Availability of components, high etching speed, safety	Not stored
	Citric acid (C 6 H 8 O 7)	30 g
	Table salt (NaCl)	5 g
Aqueous solution of ferric chloride	Water (H2O)	300 ml	IN warm water dissolve ferric chloride	Sufficient etching speed, reusable	Low availability of ferric chloride
Aqueous solution of ferric chloride	Ferric chloride (FeCl 3)	100 g	IN warm water dissolve ferric chloride	Sufficient etching speed, reusable	Low availability of ferric chloride
Hydrogen peroxide plus hydrochloric acid	Hydrogen peroxide (H 2 O 2)	200 ml	Pour 10% hydrochloric acid into a 3% hydrogen peroxide solution.	High etching rate, reusable	Great care required
Hydrogen peroxide plus hydrochloric acid	Hydrochloric acid (HCl)	200 ml		High etching rate, reusable	Great care required
Aqueous solution of copper sulfate	Water (H2O)	500 ml	IN hot water(50-80°C) dissolve table salt, and then copper sulfate	Component Availability	The toxicity of copper sulfate and slow etching, up to 4 hours
	Copper sulfate(CuSO4)	50 g
	Table salt (NaCl)	100 g

Etch printed circuit boards in metal utensils not allowed. To do this, you need to use a container made of glass, ceramic or plastic. The used etching solution may be disposed of in the sewer system.

Etching solution of hydrogen peroxide and citric acid

A solution based on hydrogen peroxide with citric acid dissolved in it is the safest, most affordable and fastest working. Of all the solutions listed, this is the best by all criteria.

Hydrogen peroxide can be purchased at any pharmacy. Sold in the form of a liquid 3% solution or tablets called hydroperite. To obtain a liquid 3% solution of hydrogen peroxide from hydroperite, you need to dissolve 6 tablets weighing 1.5 grams in 100 ml of water.

Citric acid in the form of crystals is sold in any grocery store, packaged in bags weighing 30 or 50 grams. Table salt can be found in any home. 100 ml of etching solution is enough to remove 35 micron thick copper foil from a printed circuit board with an area of 100 cm 2. The spent solution is not stored and reuse is not subject to. By the way, citric acid can be replaced with acetic acid, but because of its pungent odor, you will have to etch the printed circuit board outdoors.

Ferric chloride pickling solution

The second most popular etching solution is an aqueous solution of ferric chloride. Previously, it was the most popular, since on any industrial enterprise ferric chloride was easy to obtain.

The etching solution is not demanding on temperature; it etches quickly enough, but the etching rate decreases as the ferric chloride in the solution is consumed.

Ferric chloride is very hygroscopic and therefore quickly absorbs water from the air. As a result, a yellow liquid appears at the bottom of the jar. This does not affect the quality of the component and such ferric chloride is suitable for preparing an etching solution.

If the used ferric chloride solution is stored in an airtight container, it can be reused many times. Subject to regeneration, just pour iron nails into the solution (they will immediately be covered with a loose layer of copper). If it gets on any surface, it leaves hard-to-remove yellow stains. Currently, ferric chloride solution is used less frequently for the manufacture of printed circuit boards due to its high cost.

Etching solution based on hydrogen peroxide and hydrochloric acid

Excellent etching solution, provides high speed etching. Hydrochloric acid, with vigorous stirring, is poured into a 3% aqueous solution of hydrogen peroxide in a thin stream. It is unacceptable to pour hydrogen peroxide into acid! But due to the presence of hydrochloric acid in the etching solution, great care must be taken when etching the board, since the solution corrodes the skin of the hands and spoils everything it comes into contact with. For this reason, it is not recommended to use an etching solution with hydrochloric acid at home.

Etching solution based on copper sulfate

The method of manufacturing printed circuit boards using copper sulfate is usually used if it is impossible to produce an etching solution based on other components due to their inaccessibility. Copper sulfate is a pesticide and is widely used for pest control in agriculture. In addition, the etching time of the printed circuit board is up to 4 hours, while it is necessary to maintain the solution temperature at 50-80°C and ensure a constant change of the solution at the surface being etched.

PCB etching technology

For etching a board in any of the above etching solutions, glass, ceramic or plastic dishes, for example from dairy products. If you don’t have a suitable size container at hand, you can take any box of thick paper or cardboard of a suitable size and line its inside plastic film. An etching solution is poured into the container and a printed circuit board is carefully placed on its surface, pattern down. Due to the forces of surface tension of the liquid and its light weight, the board will float.

For convenience, you can glue a plastic bottle cap to the center of the board with instant glue. The cork will simultaneously serve as a handle and a float. But there is a danger that air bubbles will form on the board and the copper will not be etched in these places.

To ensure uniform etching of copper, you can place the printed circuit board on the bottom of the container with the pattern facing up and periodically shake the tray with your hand. After some time, depending on the etching solution, areas without copper will begin to appear, and then the copper will completely dissolve on the entire surface of the printed circuit board.

After the copper is completely dissolved in the etching solution, the printed circuit board is removed from the bath and thoroughly washed under running water. running water. Toner is removed from the tracks with a rag soaked in acetone, and paint is easily removed with a rag soaked in a solvent that was added to the paint to obtain the desired consistency.

Preparing the printed circuit board for installation of radio components

The next step is to prepare the printed circuit board for the installation of radio elements. After removing the paint from the board, the tracks need to be processed in a circular motion with fine sandpaper. There is no need to get carried away, because the copper tracks are thin and can be easily ground off. Just a few passes with abrasive with light pressure are enough.

Next, the current-carrying paths and contact pads of the printed circuit board are coated with alcohol-rosin flux and tinned with soft solder using an electric soldering iron. To prevent the holes on the printed circuit board from being covered with solder, you need to take a little bit of it onto the soldering iron tip.

After completing the manufacture of the printed circuit board, all that remains is to insert the radio components into the designated positions and solder their leads to the pads. Before soldering, the legs of the parts must be moistened with alcohol-rosin flux. If the legs of the radio components are long, then before soldering they need to be cut with side cutters to a protrusion length above the surface of the printed circuit board of 1-1.5 mm. After completing the installation of parts, you need to remove any remaining rosin using any solvent - alcohol, white alcohol or acetone. They all successfully dissolve rosin.

It took no more than five hours to implement this simple capacitive relay circuit from laying out the tracks for manufacturing a printed circuit board to creating a working sample, much less than it took to type up this page.

When a laser printer is available, radio amateurs use a printed circuit board manufacturing technology called LUT. However, such a device is not available in every home, since even in our time it is quite expensive. There is also a manufacturing technology using photoresist film. However, to work with it you also need a printer, but an inkjet one. It’s already simpler, but the film itself is quite expensive, and at first it’s better for a novice radio amateur to spend the available funds on a good soldering station and other accessories.
Is it possible to make a printed circuit board of acceptable quality at home without a printer? Yes. Can. Moreover, if everything is done as described in the material, you will need very little money and time, and the quality will be at a very high level. In any case, the electric current will “run” along such paths with great pleasure.

List of necessary tools and consumables

You should start by preparing the tools, devices and consumables that you simply cannot do without. To realize the most budget method To make printed circuit boards at home, you will need the following:

Software for drawing design.
Transparent polyethylene film.
Narrow tape.
Marker.
Foil fiberglass.
Sandpaper.
Alcohol.
Unnecessary toothbrush.
Tool for drilling holes with a diameter of 0.7 to 1.2 mm.
Ferric chloride.
Plastic container for etching.
Brush for painting with paints.
Soldering iron.
Solder.
Liquid flux.

Let’s go through each point briefly, since there are some nuances that can only be reached through experience.
Today there are a huge number of programs for developing printed circuit boards, but for a novice radio amateur the most simple option will be Sprint Layout. The interface is easy to master, it is free to use, and there is a huge library of common radio components.
Polyethylene is needed to transfer the pattern from the monitor. It is better to take a stiffer film, for example, from old covers for school books. Any tape will be suitable for attaching it to the monitor. It’s better to take a narrow one - it will be easier to peel off (this procedure does not harm the monitor).
It’s worth looking at markers in more detail, as this is a sore subject. In principle, any option is suitable for transferring a design onto polyethylene. But to draw on foil fiberglass, you need a special marker. But there is a little trick to save money and not buy quite expensive “special” markers for drawing printed circuit boards. The fact is that these products are absolutely no different in their properties from ordinary permanent markers, which are sold 5-6 times cheaper in any office supply store. But the marker must have the inscription “Permanent”. Otherwise nothing will work.

You can take any foiled fiberglass laminate. It's better if it's thicker. For beginners, working with such material is much easier. To clean it, you will need sandpaper with a grit size of about 1000 units, as well as alcohol (available at any pharmacy). The last consumable can be replaced with nail polish mixing liquid, which is available in any house where a woman lives. However, this product smells quite nasty and takes a long time to dissipate.
To drill the board, it is better to have a special mini-drill or engraver. However, you can go a cheaper route. It is enough to buy a collet or jaw chuck for small drills and adapt it to a regular household drill.
Ferric chloride can be replaced with others chemicals, including those that you probably already have in your home. For example, a solution of citric acid in hydrogen peroxide is suitable. Information on how alternative compositions to ferric chloride are prepared for etching boards can be easily found on the Internet. The only thing worth paying attention to is the container for such chemicals - it should be plastic, acrylic, glass, but not metal.
There is no need to talk in more detail about the soldering iron, solder and liquid flux. If a radio amateur has come to the question of making a printed circuit board, then he is probably already familiar with these things.

Development and transfer of the board design to the template

When all of the above tools, devices and Consumables prepared, you can start developing the board. If the device being manufactured is not unique, then it will be much easier to download its design from the Internet. Even a regular drawing in JPEG format will do.

If you want to go a more complicated route, draw the board yourself. This option is often unavoidable, for example, in situations where you do not have exactly the same radio components that are needed to assemble the original board. Accordingly, when replacing components with analogues, you have to allocate space for them on fiberglass, adjust holes and tracks. If the project is unique, then the board will have to be developed from scratch. This is what the above-mentioned software is needed for.
When the board layout is ready, all that remains is to transfer it to a transparent template. The polyethylene is fixed directly to the monitor using tape. Next, we simply translate the existing pattern - tracks, contact patches, and so on. For these purposes, it is best to use the same permanent marker. It does not wear off, does not smear, and is clearly visible.

Preparation of foil fiberglass laminate

The next stage is the preparation of fiberglass. First you need to cut it to the size of the future board. It is better to do this with a small margin. To cut foiled fiberglass laminate, you can use one of several methods.
Firstly, the material can be cut perfectly using a hacksaw. Secondly, if you have an engraver with cutting wheels, it will be convenient to use it. Thirdly, fiberglass can be cut to size using a utility knife. The principle of cutting is the same as when working with a glass cutter - a cutting line is applied in several passes, then the material is simply broken off.

Now you definitely need to clean the copper layer of fiberglass from protective coating and oxide. The best way There is no better way to solve this problem than using sandpaper. The grain size is taken from 1000 to 1500 units. The goal is to obtain a clean, shiny surface. It is not worth stripping the copper layer to a mirror shine, since small scratches from sandpaper increases surface adhesion, which will be needed later.
Finally, all that remains is to clean the foil from dust and fingerprints. To do this, use alcohol or acetone (nail polish remover). After processing, we do not touch the copper surface with our hands. For subsequent manipulations, we grab the fiberglass by the edges.

Combination of template and fiberglass

Now our task is to combine the pattern obtained on polyethylene with the prepared fiberglass laminate. To do this, the film is applied to the desired location and positioned. The remains are wrapped on the reverse side and secured with the same tape.

Drilling holes

Before drilling, it is recommended to secure the fiberglass laminate with the template to the surface in some way. This will allow for greater accuracy and will also prevent sudden rotation of the material as the drill passes through. If you have a drilling machine for such work, then the problem described will not arise at all.

You can drill holes in fiberglass at any speed. Some work at low speeds, others at high speeds. Experience shows that the drills themselves last much longer if operated at low speeds. This makes them more difficult to break, bend and damage the sharpening.
The holes are drilled directly through the polyethylene. Future contact patches drawn on the template will serve as reference points. If the project requires it, we promptly change drills to the required diameter.

Drawing tracks

Next, the template is removed, but not thrown away. TO copper coating We still try not to touch with our hands. To draw paths we use a marker, always permanent. It is clearly visible from the trail it leaves. It is better to draw in one pass, since after the varnish, which is included in the permanent marker, has hardened, it will be very difficult to make edits.

We use the same polyethylene template as a guide. You can also draw in front of the computer, checking the original layout, where there are markings and other notes. If possible, it is better to use several markers with tips of different thicknesses. This will allow you to draw both thin paths and extensive polygons more efficiently.

After applying the drawing, be sure to wait some time necessary for the final hardening of the varnish. You can even dry it with a hairdryer. The quality of future tracks will depend on this.

Etching and cleaning marker tracks

Now comes the fun part - etching the board. There are several nuances here that few people mention, but they significantly affect the quality of the result. First of all, prepare the ferric chloride solution according to the recommendations on the package. Usually the powder is diluted with water in a ratio of 1:3. And here's the first piece of advice. Make the solution more saturated. This will help speed up the process, and the drawn paths will not fall off before everything necessary is etched out.

Immediately the second tip. It is recommended to immerse the bath with the solution in hot water. You can heat it in a metal bowl. An increase in temperature, as is known since school curriculum, significantly speeds up the chemical reaction, which is what etching our board is. Reducing the procedure time is to our advantage. The tracks made with a marker are quite unstable, and the less they sour in the liquid, the better. If at room temperature The board is etched in ferric chloride for about an hour, but in warm water this process is reduced to 10 minutes.
In conclusion, one more piece of advice. During the etching process, although it is already accelerated due to heating, it is recommended to constantly move the board, as well as clean off the reaction products with a drawing brush. By combining all the manipulations described above, it is quite possible to etch out excess copper in just 5-7 minutes, which is simply an excellent result for this technology.

At the end of the procedure, the board must be thoroughly rinsed under running water. Then we dry it. All that remains is to wash away the traces of the marker that are still covering our paths and patches. This is done with the same alcohol or acetone.

Tinning of printed circuit boards

Before tinning, be sure to go over the copper layer again with sandpaper. But now we do it extremely carefully so as not to damage the tracks. The simplest and affordable way tinning - traditional, using a soldering iron, flux and solder. Rose or Wood alloys can also be used. There is also so-called liquid tin on the market, which can greatly simplify the task.
But all these new technologies require additional costs and some experience, so for the first time it will be suitable classic method tinning. Liquid flux is applied to the cleaned tracks. Next, solder is collected onto the soldering iron tip and distributed over the copper remaining after etching. It is important to warm up the traces here, otherwise the solder may not “stick”.

If you still have Rose or Wood alloys, then they can be used outside the technology. They melt just fine with a soldering iron, are easily distributed along the tracks, and do not bunch up, which will only be a plus for a novice radio amateur.

Conclusion

As can be seen from the above, the budget technology for manufacturing printed circuit boards at home is truly accessible and inexpensive. You don't need a printer, an iron, or expensive photoresist film. Using all the tips described above, you can easily make the simplest electronic radios without investing a lot of money in it, which is very important in the first stages of amateur radio.

Printed circuit board– this is a dielectric base, on the surface and in the volume of which conductive paths are applied in accordance with the electrical circuit. The printed circuit board is intended for mechanical fastening and electrical connection between the leads of electronic and electrical products installed on it by soldering.