How to draw tracks on the board for etching. An easy way to make printed circuit boards (not LUT)

The topic of making boards is not new, and even more so drawing with a marker or varnish, but there are few places in my city where you can buy a marker. Yes, and in almost all stores they are the same - I ran around all the stores, and I didn’t find a new one, there are only 2 types of markers, well, they are also multi-colored, but they definitely don’t suit us. Today we will test such a set of markers for drawing printed circuit boards: 2 pens and nail polish (of course, it is out of competition).

For the experiment, I took a piece of textolite, sanded it and began to draw something. It turned out something like this, I’ll say right away that our test is brutal and not adequate, but it will already make it clear what’s what. The board was left to be poisoned for six hours.

Now let's talk about the results and experimental plates in more detail.

The colored blue marker used to be nothing, it doesn’t protect the textolite, what’s with it, what’s without it, and it dried up, I dismantled it, but kept the case, it’s just perfect for a dialing device in such a case, but now it’s not about him.

• Marker, the most that is not an ordinary black marker
• CD Signing Marker
• Two different pens - not helium
• And of course nail polish.

So, as you can see, the varnish did the best job, but it’s not convenient for them to draw boards, only paint on them.

Next, a CD marker, it did a good job, and if you do not keep it in the solution for 5 hours, then it copes no worse than varnish. There is one feature in it - the drawing part is thin, it is protected by plastic a little higher and it is a pleasure to draw under the ruler.

The habit marker did the same as the previous one, only it will have a slightly larger drawing tip, but it also turns out not very badly.

Now the pens. There was no trace left of the pens, I once had a gel pen, so she drew in such a way that it was a feast for the eyes! It turned out tracks from 0.4 mm, only it disappeared somewhere, during the tests I remembered this and decided to check how the current pens draw.

Lacquer here is only one plus, and if you fill it in a jar from a sweat-corrector, then in general a thermonuclear thing comes out for drawing circuit boards! I have enough markers, and this is so - note.

A printed circuit board is a sheet of insulating material, usually fiberglass, on one or both sides of which there are conductive, usually copper, tracks. Parts are inserted into holes in the board and soldered to these tracks. The conductive tracks are arranged so that if you insert them correctly into the right holes and solder well, then these tracks will connect the parts together in such a way that you get some kind of electronic device.

There is also surface mounting, when the parts are located on the same side as the printed tracks, and soldered to them without pushing the leads into the holes. This method is most often used in very compact devices, when mounting miniature parts. At home, so to speak, in the kitchen, it is easier to make the first option. About him and will be discussed here.

There are many ways and methods for manufacturing printed circuit boards in "kitchen" conditions, described in various amateur radio literature. Here, without pretending to be original, one of them is considered, suitable for the manufacture of printed circuit boards for simple electronic devices. As an example, let's make a board for the buzzer described in this magazine in the article "Electronic bell for a bicycle." In order not to leaf through the magazine once again, the timer circuit, as well as the printed circuit board drawing and the wiring diagram, are repeated here in figures 1,2 and 3, respectively.

Drawing preparation

But, before you engage in the manufacture of a printed circuit board, you need to find out on what scale its drawing is given. In radio magazines, the drawing is almost always given on a scale of 1: 1. But it varies from edition to edition.

If the board drawing is given on a different scale, it must be redrawn or redrawn on a scale grid so that an image is obtained on a 1:1 scale. Here the image is immediately on a 1:1 scale, and nothing needs to be reduced or enlarged.

PCB material

The main material for printed circuit boards is foil fiberglass. This is an insulating sheet on which copper foil is glued on one or both sides. You need to cut a blank from this sheet - a piece is slightly larger than the printed circuit board. It is usually recommended to cut with a metal saw, but with sufficient physical strength, this can be done with metal shears - it will be faster and with less sweat.

Then, the foil must be carefully sanded with a fine sandpaper - zero, but not to holes, but so as to remove only a layer of oxides. No need to achieve a mirror shine, let it be better to have a lot of small scratches. The essence of further actions is to protect the necessary sections of the foil from the etching solution.

Transferring a picture

Now you need to transfer figure 2 to this foil. The easiest way to do this is with an awl, a light hammer, carbon paper (“carbon paper”, which is placed between sheets of paper to write several sheets at once), and a ballpoint pen.

Rice. 1. Diagram of a simple electronic device.

Rice. 2. A printed circuit board for an electronic device.

Rice. 3. The layout of the components on the printed circuit board.

It is necessary to put the workpiece under the sheet with the image of the tracks (Fig. 2). However, you can first make a photocopy so as not to spoil the magazine. Then, between the sheet with the image of the tracks and the workpiece, lay a “carbon paper” with the coloring side to the workpiece. With the help of paper clips, or in another way, fix this “sandwich”.

Next, with the help of an awl and a light hammer, you need to slightly, slightly, pinch the points where there should be holes. Then, using a ballpoint pen, draw the tracks so that their contours pass through the carbon paper to the workpiece. Now we disassemble the "sandwich".

Hole drilling

We take a microdrill (an electric screwdriver or a small screwdriver will do as a microdrill), and with a metal drill with a diameter of 1-1.2 mm we drill holes in the pinned places. It is better to blow off sawdust, and not brush it off with your hand, otherwise you can erase the pattern from the "carbon paper". Do not touch the surface of the board from the side of the foil, because the fingers leave "sweat-fat" traces, which in the future may interfere with etching.

Drawing tracks

The next step is drawing the tracks themselves. There are many ways to do this. You can use nail polish (with an appropriate brush), "zapon-lacquer", nitro-paint, bituminous varnish. At the same time, the writing instrument is a brush for nail polish, a drawing pen, a drawing pen, a sharply sharpened match.

But all this has gone into a deep dense past, after felt-tip pens (markers) for writing on CDs and DVDs appeared in stationery stores.

This, one might say, "revolutionized the kitchen industry" of printed circuit boards. We take a marker "For CD" or "For DVD" of black thick color, fresh, "delicious" smelling either of alcohol or acetic acid, and scrupulously draw mounting pads and print tracks with it, painting their surface densely, in several layers.

At the same time, the rest of the surface must be left unpainted (and not patched). The "For CD" or "For DVD" marker dries instantly, so the workpiece is ready for etching as soon as the painting process is complete.

Track etching

The most suitable reagent for etching is a solution of ferric chloride. Now ferric chloride in powder form is sold almost everywhere in the same place as radio components. You need to dilute 50-60 grams per glass of warm water.

Stir with a non-metallic object (an ordinary metal teaspoon is convenient, of course, but it will ruin everything and spoil itself). Then, having made a small hole in the corner of the board not occupied by the tracks, you can hang this board for it on a nylon fishing line and lower it into this same glass (the glass must be non-metallic).

So that the board is somewhere in the middle of the glass, completely covered with a solution of ferric chloride. After all the unpainted foil has dissolved, remove the workpiece, rinse with water. Wash off the marker paint with any alcohol-containing liquid, for example ... cheap cologne.

Rinse again with water, dry with a hair dryer and you can arrange the parts according to Figure 3 and solder.

The pages of the site have already talked about the so-called "pencil technology" for the manufacture of printed circuit boards. The method is simple and affordable - a corrective pencil can be bought at almost any store that sells office supplies. But there are also limitations. Those who tried to draw a printed circuit board pattern with a correction pencil noticed that the minimum width of the resulting track is unlikely to be less than 1.5-2.5 millimeters.

This circumstance imposes restrictions on the manufacture of printed circuit boards that have thin tracks and a small distance between them. It is known that the pitch between the pins of microcircuits made in a surface mount package is very small. Therefore, if you want to make a printed circuit board with thin tracks and a small distance between them, then the “pencil” technology will not work. It is also worth noting that drawing a drawing with a corrective pencil is not very convenient, the tracks are not always even, and the copper patches for soldering the leads of radio components do not come out very neat. Therefore, you have to correct the pattern of the printed circuit board with a sharp razor blade or scalpel.

The way out of this situation can be to use a PCB marker, which is great for applying an etch-resistant layer. Out of ignorance, you can purchase a marker for applying inscriptions and marks on CD / DVD discs. Such a marker is not suitable for the manufacture of printed circuit boards - a solution of ferric chloride corrodes the pattern of such a marker, and the copper tracks are almost completely etched. But, despite this, there are markers on sale that are suitable not only for applying inscriptions and marks on various materials (CD / DVDs, plastic, wire insulation), but also for making a protective layer resistant to etching.

In practice, a marker for printed circuit boards was used Edding 792. It allows you to draw lines with a width of 0.8-1 mm. This is enough to produce a large number of printed circuit boards for homemade electronic devices. As it turned out, this marker perfectly copes with the task. The printed circuit board turned out pretty good, although it was drawn in a hurry. Take a look.

PCB (made with Edding 792 marker)

By the way, the Edding 792 marker can also be used to correct errors and blots that resulted from transferring a printed circuit board pattern to a workpiece using the LUT method (laser ironing technology). This happens, especially if the printed circuit board is quite large and has a complex pattern. This is very convenient, since there is no need to completely transfer the entire pattern to the workpiece again.

If you cannot find the Edding 792 marker, then it will do. Edding 791, Edding 780. They can also be used to draw printed circuit boards.

Surely, novice electronics lovers are interested in the technological process of manufacturing a printed circuit board using a marker, so the story will go on about this.

The whole process of manufacturing a printed circuit board is similar to that described in the article "Manufacturing a printed circuit board using the "pencil" method". Here is a short algorithm:

A few "subtleties".

About drilling holes.

There is an opinion that it is necessary to drill holes in the printed circuit board after etching. As you can see, in the above algorithm, drilling holes is before etching the printed circuit board in the solution. In principle, you can drill even before etching the printed circuit board, even after. From a technological point of view, there are no restrictions. But, it should be borne in mind that the quality of drilling directly depends on the tool with which the holes are drilled.

If the drilling machine develops good speed and there are high-quality drills available, then you can drill after etching - the result will be good. But, if you drill holes in the board with a self-made mini-drill based on a weak motor with poor alignment, then you can easily tear off the copper patches for the leads.

Also, much depends on the quality of the textolite, getinaks or fiberglass. Therefore, in the above algorithm, drilling holes is before etching the printed circuit board. With this algorithm, the copper edges remaining after drilling can be easily removed with sandpaper and at the same time clean the copper surface from contamination, if any. As is known, the contaminated surface of copper foil is poorly etched in solution.

How to dissolve the protective layer of the marker?

After etching in a solution, the protective layer, which was applied with the Edding 792 marker, can be easily removed with a solvent. In fact, white spirit was used. It stinks, of course, disgustingly, but the protective layer washes off with a bang. No varnish residue remains.

Preparation of the printed circuit board for tinning copper tracks.

After the protective layer is removed, you can for a few seconds throw the printed circuit board blank into the solution again. At the same time, the surface of the copper tracks will be slightly etched and become a bright pink color. Such copper is better covered with solder during subsequent tinning of the tracks, since there are no oxides and small contaminants on its surface. True, the tinning of the tracks must be done immediately, otherwise the copper in the open air will again be covered with a layer of oxide.

Finished device after assembly

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 designed for mechanical fastening and electrical connection between each other by soldering the leads of electronic and electrical products installed on it.

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

Manual application technology
PCB tracks

Template preparation

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

Cutting a workpiece

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

Next, fiberglass is cut along the marked lines using metal scissors or cut with a hacksaw. Scissors cut faster and no dust. But it must be taken into account that when cutting with scissors, fiberglass is strongly bent, which somewhat worsens the strength of gluing copper foil, and if re-soldering of the elements is required, the tracks may peel off. Therefore, if the board is large and with very thin tracks, then it is better to cut it off with a hacksaw.

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

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

Hole drilling

It is best to drill holes using a special mini drilling machine with a 0.7-0.8 mm carbide drill. If a mini drilling machine is not available, then you can drill holes with a low-power drill with a simple drill. But when working with a universal hand drill, the number of broken drills will depend on the hardness of your hand. One drill is definitely not enough.

If the drill cannot be clamped, then its shank can be wrapped with several layers of paper or one layer of sandpaper. It is possible to wind tightly coil to coil of a thin metal wire on the shank.

After drilling is completed, it is checked whether all holes have been drilled. This is clearly visible if you look at the printed circuit board through the light. As you can see, there are no missing holes.

Drawing a topographic drawing

In order to protect the places of the foil on the fiberglass, which 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 tracks, it is better to pre-mark them with a soft, simple pencil or marker.

Before marking, it is necessary to remove traces of Moment glue, which glued 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 with a rag with any agent, such as acetone or white spirit (as refined gasoline is called), and any dishwashing detergent, such as Ferry, can also be used.

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

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

Drawing a picture 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 drawer of the ballerina to the required line width and to set the diameter of the circle, adjust the second screw by moving the drawer from the axis of rotation.

Next, the drawer of the ballerina for a length of 5-10 mm is filled with paint with a brush. For applying a protective layer on a printed circuit board, paint of the PF or GF brand is best suited, as it dries slowly and allows you to work calmly. NC brand paint can also be used, but it is difficult to work with it, as it dries quickly. The paint should lay down well and not spread. Before drawing, the paint must be diluted to a liquid consistency, adding a suitable solvent to it little by little with vigorous stirring and trying to draw on scraps of fiberglass. To work with paint, it is most convenient to pour it into a nail polish bottle, in the twist of which a solvent-resistant brush is installed.

After adjusting the drawer of the ballerina and obtaining the required line parameters, you can begin to apply 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, circles of perfectly round shape are obtained. When the ballerina begins to draw poorly, the remnants of dried paint are removed from the drawer gap with a cloth and the drawer is filled with fresh paint. to outline 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.

When the round contact pads on the board are drawn, you can start drawing conductive tracks using a manual drawing pen. The preparation and adjustment of a manual drawing pen is no different from the preparation of a ballerina.

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

So that the printed circuit board does not slip when drawing tracks, it is advisable to place it on a sheet of sandpaper, which is two sandpaper sheets riveted together with paper sides.

If, when drawing paths and circles, they touched, then no action should be taken. It is necessary to allow the paint on the printed circuit board to dry to a state where it will not stain when touched, and use the edge of a knife to remove the excess part of the pattern. In order for the paint to dry faster, the board must be placed in a warm place, for example, in winter, on a radiator. In the summer season - under the rays of the sun.

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

Printed circuit board drawing technology
using a laser printer

When printing on a laser printer, the image formed by the toner is transferred electrostatically from the photo drum, on which the laser beam painted 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 texture of the paper. After cooling, 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 the toner is used to transfer the image of current-carrying tracks to a printed circuit board at home.

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

Preparing a paper template for transferring a pattern to a printed circuit board

If you print a printed circuit board pattern 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 with 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, such as photographic paper, a substrate from self-adhesive films and labels, tracing paper, pages from glossy magazines.

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

This technique allows you to print a printed circuit board pattern even on the thinnest paper or film. In order for the toner thickness of the pattern 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 roughest type of paper, such as cardboard or something like that. It is quite possible that you will not get a good print the first time, and you will have to experiment a little, choosing the best print mode for a laser printer. In the resulting print of the pattern, the tracks and contact pads of the printed circuit board must be dense without gaps and smearing, since retouching at this technological stage is useless.

It remains to cut the tracing paper along the contour and the template for the manufacture of the printed circuit board will be ready and you can proceed to the next step, transferring the image to the fiberglass.

Transferring a pattern from paper to fiberglass

Transferring the PCB pattern 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 the fiberglass and pressed with great effort. 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 pattern remains on the printed circuit board.

Some craftsmen suggest transferring a pattern 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 the desired temperature and evenly press the paper against the entire surface of the printed circuit board when the toner solidifies. As a result, the pattern is not completely transferred and there are gaps in the pattern of PCB tracks. It is possible that the iron did not heat up enough, although the regulator was set to the maximum heating of the iron. I did not want to open the iron and reconfigure the thermostat. Therefore, I used another technology that is less laborious and provides a 100% result.

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

It remains to heat the made 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 for cooling.

If an electric oven is not available, then you can also use a gas oven by adjusting the temperature with the gas supply knob according to the built-in thermometer. If there is no thermometer or it is faulty, then women can help, the position of the regulator knob, at which pies are baked, will do.

Since the ends of the plywood were warped, just in case, I clamped them with additional clamps. 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 the printed circuit boards, tighten the plates with screws and nuts. M10 will be enough.

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

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

Etching a printed circuit board at home is best in a solution of ferric chloride or hydrogen peroxide with citric acid. After etching, the toner from the printed tracks is easily removed with a swab dipped in acetone.

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

This form was taken by a printed circuit board with radio components installed on it. The result was a power supply and switching unit for an electronic system that complements an ordinary toilet bowl with a bidet function.

PCB etching

To remove copper foil from unprotected areas of foil fiberglass in the manufacture of printed circuit boards at home, radio amateurs usually use a 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.

Etching solution recipes

Depending on the availability of components, radio amateurs use one of the solutions shown in the table below. Etching solutions are listed in order of popularity for their use by radio amateurs in the home.

Solution name	Composition	Quantity	Cooking technology	Advantages	disadvantages
Hydrogen peroxide plus citric acid	Hydrogen peroxide (H 2 O 2)	100 ml	Dissolve citric acid and table salt in a 3% hydrogen peroxide solution	Availability of components, high pickling rate, safety	Not stored
	Citric acid (C 6 H 8 O 7)	30 g
	Salt (NaCl)	5 g
Aqueous solution of ferric chloride	Water (H2O)	300 ml	Dissolve ferric chloride in warm water	Sufficient etching rate, reusable	Low availability of ferric chloride
	Ferric chloride (FeCl 3)	100 g
Hydrogen peroxide plus hydrochloric acid	Hydrogen peroxide (H 2 O 2)	200 ml	Pour 10% hydrochloric acid into a 3% hydrogen peroxide solution	High pickling rate, reusable	Requires high precision
	Hydrochloric acid (HCl)	200 ml
Aqueous solution of copper sulphate	Water (H2O)	500 ml	In hot water (50-80 ° C), dissolve table salt, and then blue vitriol	Component Availability	The toxicity of copper sulfate and slow etching, up to 4 hours
	Copper sulfate (CuSO 4)	50 g
	Salt (NaCl)	100 g

Etch printed circuit boards in metal utensils are not allowed. To do this, use a container made of glass, ceramic or plastic. It is allowed to dispose of the spent pickling solution into the sewer.

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 listed solutions, by all criteria, this is the best.

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 pickling solution is enough to remove 35 µm thick copper foil from a 100 cm2 printed circuit board. The spent solution is not stored and cannot be reused. By the way, citric acid can be replaced with acetic acid, but because of its pungent smell, you will have to pickle the printed circuit board in the open air.

Pickling solution based on ferric chloride

The second most popular pickling solution is an aqueous solution of ferric chloride. Previously, it was the most popular, since ferric chloride was easy to get at any industrial enterprise.

The etching solution is not picky about the temperature, it etchs rather quickly, 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 the preparation of an etching solution.

If the used solution of ferric chloride is stored in an airtight container, then it can be used repeatedly. To be regenerated, it is enough to pour iron nails into the solution (they will immediately be covered with a loose layer of copper). Leaves hard-to-remove yellow spots upon contact with any surface. At present, a solution of ferric chloride for the manufacture of printed circuit boards is used less frequently due to its high cost.

Etching solution based on hydrogen peroxide and hydrochloric acid

Excellent pickling solution, provides high pickling speed. Hydrochloric acid, with vigorous stirring, is poured into a 3% aqueous solution of hydrogen peroxide in a thin stream. Pouring hydrogen peroxide into acid is unacceptable! 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 gets on. For this reason, an etching solution with hydrochloric acid at home is not recommended.

Etching solution based on copper sulphate

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

PCB etching technology

For etching the board in any of the above etching solutions, glass, ceramic or plastic utensils, such as dairy products, are suitable. If there is no suitable container size at hand, then you can take any box made of thick paper or cardboard of a suitable size and line its inside with plastic wrap. An etching solution is poured into the container and a printed circuit board is carefully placed on its surface with a pattern down. Due to the forces of the surface tension of the liquid and the low weight, the board will float.

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

To ensure uniform etching of copper, you can put the printed circuit board on the bottom of the tank with the pattern up and periodically shake the bath with your hand. After a while, depending on the pickling 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 final dissolution of copper in the pickling solution, the printed circuit board is removed from the bath and thoroughly washed under running water. The toner is removed from the tracks with a rag soaked in acetone, and the paint is well 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 the 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 must be processed in a circular motion with fine sandpaper. You don’t need to get carried away, because the copper tracks are thin and can be easily grinded off. Just a few passes with a low-pressure abrasive is sufficient.

Further, the current-carrying tracks and contact pads of the printed circuit board are covered with an alcohol-rosin flux and tinned with soft solder with an electric soldering iron. so that the holes on the printed circuit board are not tightened with solder, you need to take a little of it on the soldering iron tip.

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

This simple capacitive relay circuit took no more than five hours to complete from the PCB traces to a working prototype, much less than the layout of this page.

lupo, well so continue in the same way, especially since the fee is on order, and, obviously, time is limited, and you will spend quite a lot of time on mastering the LUT. My "secrets" from the time when I painted with paint:

A) the use of an insulin syringe with a sharpened (not bitten!) up to 4-5 mm removable thin (pink) needle.
b) the use of not nitro-paints, but PF enamels diluted with appropriate solvents (in no case with acetone and acetone-containing solvents! - contrary to seeming logic, PF diluted with acetone will dry for a week).
c) a sufficiently liquid dilution of the enamel and adjustment of the "feed" by inserting a wire into the needle - the diameter is selected experimentally - to prevent spontaneous leakage of "ink". For the same purpose, it is undesirable to fill the syringe more than 2-3 mm above the level of the needle. In this case, the paint is "sucked out" from the needle due to the capillary effect only when drawing. You need to have a piece of cardboard at hand - even with a short break, you will have to "paint" the needle by blowing the syringe, and at the same time a drop will crawl out, which, when you try to "paint" the syringe directly on the board, will lead to a blot.
d) first, ALL nickels of contact pads are outlined, then the board is given time to dry until the state of "non-sticking" to the nickels of the ruler - at least 3 hours)
e) drawing lines is carried out under the ruler with the lower edge beveled inward - to prevent paint from leaking. At the same time, according to the project, horizontal lines are first drawn (with a margin on both sides - PF, unlike nitra, is good because it is easier to clean it carefully until it is completely dry (even under the ruler, which is very convenient when cleaning up "grids" formed with this technology, for example, on the turns of multi-bit tires), then the board is given time to dry, and then vertical lines are drawn. BALLPOINT PEN marks are made - for subsequent drawing.
f) after the verticals have dried, if necessary, the diagonals are drawn, and smudges, "tails" of the horizontals, etc. can be cleaned up immediately. The advantage of PF is that it retains plasticity for a rather long time, and does not chip off during stripping, unlike nitra. Thanks to this, with a practiced skill, you can QUIETLY “pull” two tracks between the legs of the microcircuit with a step of 2.5 mm. A 0.5 mm track, subject to these recommendations, is the standard track width, with VERY great painstaking work, careful selection of paint density and the diameter of the wire-insert, 0.3 mm can be pulled out. Will merge with nickels of legs? Yes, and X with them - after drying, the insulating gaps are calmly and without tension "finished" with a scraper. Do not try to fix the leaks IMMEDIATELY - this will only lead to dirt on the board! Let them dry (I usually marked the resulting "streaks" that required subsequent attention in the drawing-project with a marker-highlighter, and eliminated it after FULL drawing of the board tracks).
g) let the board dry for at least 4 hours, at least until the feeling of "sticking" of the finger to the last drawn tracks disappears.
h) Well, that's it ... Next - ferric chloride, final inspection and, if necessary, cleaning. The strength of the paint makes it possible, with a high uneven wiring (a very dense pattern with thin tracks in some places, and large etched areas in others), to avoid etching the already etched tracks, stop the general mixing of the solution and apply manual forced (foam swab) on large etched surfaces.
i) I wash off the paint from the etched board not with a solvent, but under a tap - using a piece of burlap and "Pemoxol" (or any other abrasive detergent) - this allows immediately after washing off the paint and blotting the drops from the board, irradiate it with a soldering iron, dousing it with alcohol-rosin flux ( better - activated LTI-120)
j) Enjoy!

Nostalgia ... I haven't used this method for years now ... And if you have time and a laser printer - ask in the Search on forums or in Google a request LUT(Laser-Iron Technology), and there will be happiness. With perfected skills (not a single recommendation is dogma, a lot depends on the printer, media, paper and personal preferences), this technology allows you to get boards with a quality even higher than industrial silk-screen printing, with a very stable result. I’ll add a secret from myself, which for some reason was omitted in the “educational programs” for LUT - with this technology, wide (power) tracks and large shaded areas are printed rather poorly - very ugly spot etching occurs. In this case, I usually draw all the tracks wider than 1 mm in the project and draw the "islands" of the foil only with a contour (0.5 mm line), after printing the drawing on the board, painting over the inter-contour space classically - with a paint syringe.