Without etching. Printed circuit boards without etching

A range of technologies to control the removal of the surface layer metal part using specially selected chemicals is called metal etching. It allows you to remove scale, rust and oxides from products under the action of acids, salts and alkalis in solutions. In this way, additional preparation of metal products for joining or coating is carried out, which improves the adhesion of parts or the applied layer to the base. The most commonly used metal etching is chemical, which is carried out by immersing the workpiece in a bath with dissolved chemical reagents.

Metal chemical etching methods

There are also its types, providing for additional activation of etching substances with the help of physical factors. This metal etching is electrochemical (or galvanic) under the influence of an electric field or ion-plasma by means of ionization of reagent particles. If the word "etching" is used without specifying its type, then we are talking about chemical etching in an aqueous electrolyte. It is also called "liquid", in contrast to the "dry" ion-plasma.

When metal is etched with acid, usually sulfuric or hydrochloric, the workpiece is immersed in its solution. In this case, both the oxides existing on the surface of the part and the base metal enter into an acid reaction. From an increase in the content of acids, the dissolution operations are accelerated simultaneously for oxides and the base metal. The rate of the metal etching process, in addition to the acid concentration, is also affected by its temperature regime, as well as chemical composition oxides. The most optimal combination of these factors makes it possible to carry out etching in such a way that, with the fastest dissolution of oxides, it affects the base metal as little as possible. In addition, in artistic etching, when it is necessary to preserve the untouched part of the surface of the product, it is covered with a special protective layer.

To clean iron from surface oxides, a solution of 10% hydrochloric acid with a temperature of 40 ° C is optimal (for the use of sulfuric acid - 60 ° C). With an increase in this temperature, the rate of the process also increases. The salts obtained during metal etching can also affect the rate of the process. Some of them, such as FeCl2, increase it, while others, such as FeSO4, decrease it.

The etching of metal with ferric chloride is complicated by the production of hydrogen during the reactions of iron and acids. It interacts with the top layer of metal, forming "etching bubbles" in it and making the product more fragile. In order to prevent this effect, special additives are added to the pickling solution bath to slow down the reactions. They, creating a special shell, protect the metal from the negative effects of hydrogen.

Tanks made of concrete or wood, lined inside with acid-resistant materials, serve as the main equipment for pickling metal. For the convenience of immersing small workpieces in baths with pickling solution, special trays with baskets are used. When it is necessary to clean not the entire surface, but only part of it, for example, a brazed seam, then a brush is used to apply etching solutions to its surface. The part is then gently rinsed with water. Etching pastes are needed to clean rusty metal parts. The area affected by rust is covered in two steps with different layers of pastes, followed by rinsing.

To treat the surface of a part made of copper or its alloy, metal etching is used with nitric, hydrochloric or sulfuric acids. Aluminum parts should be etched with alkaline solutions. Nickel with alloys must be cleaned with sulfuric acid solutions with the addition of chromic anhydride. Cupronickel parts are also cleaned with a solution of sulfuric acid, adding chromium peak to it. At the same time, they need to be washed after the etching procedure with warm water, dissolving a little cream of tartar in it. In the form of etching of iron or steel products, ammonia solutions or iron sulfate are used, bronze and brass parts require metal pickling with copper sulfate, and zinc products - with zinc sulfate, as well as a solution of zinc chloride.

Features of the electrolytic etching process

Electrolytic or galvanic metal etching is used to speed up the cleaning of parts by immersion in a solution bath, which usually takes a long time. This process is much faster if metal parts are placed in an electrolytic bath in the form of cathodes or anodes. Hence the division of electrolytic etching into cathodic and anodic.

For the anodic method of metal etching, alkaline solutions of metal salts and acids are used as an electrolyte. The cathode is usually lead or, more rarely, iron, as materials that do not dissolve in the electrolyte. Given the speed of the metal etching process by electrolysis, it is necessary to strictly observe a certain regime in cleaning products by this method so as not to expose the metal to the risk of excessive electrolytic dissolution. The characteristics of the anode current are selected based on the state of the surface layer of the product, as well as the required speed of the process. Etching is carried out at room temperature. The duration of the operation is determined empirically.

The cathodic method of metal etching involves the use of lead or its alloy with antimony as an anode. In a mixture with acid solutions, alkali metal salts are an electrolyte. This technology is based on the action of hydrogen produced at the cathode. It contributes to the recovery of metals from oxides located on the part, and hydrogen in the form of a gas separates them from the surface of the metal. This etching option is not suitable for hardened steel blanks due to the possible hydrogen pickling of the surface layer of the metal part. It is possible to reduce it when using this metal etching technology by introducing tin and lead salts into the electrolyte bath.

Galvanic etching is more economical than chemical etching. This applies not only to the time spent, but also to the number of applied chemicals. In addition, the chemical composition of the etchings for such etching does not include caustic acids, therefore, gases that adversely affect health are not released during it.

Upon completion of etching, neutralization of possible residues of solutions after cleaning on the products is carried out. If this is not done, particles of salts or acids can contribute to the onset of metal corrosion. In order to remove these residues, the products are placed briefly in a solution with soda ash. After that, the parts are washed with cold and then hot water and dried. Storage of products treated in this way does not cause corrosion, but in order to avoid possible oxidation, it is better to immediately solder them.

Technologies for a beginner radio amateur

Perhaps, not a single radio amateur can do without printed wiring now, the advantages of which - a high density of parts, the reliability of the assembled circuits - are obvious.
However, inexperienced radio amateurs may have difficulties with the manufacture of printed circuit boards: first of all, you need to apply a drawing, then you need to purchase (or make) a board etching solution, in Eventually it is also necessary to have the appropriate utensils in order to place this board for etching.

But here we will present you another way of printed wiring, which does not require any drawing. no PCB etching. Ask - how is it? And like this: in the magazine Model Designer 1967 No. 5, S. BELOTSERKOVETS, A. OVSYANNIKOV from Moscow proposed an extremely simple and effective method make a printed circuit board parallel path method. Printed-parallel boards are made of foil-coated getinax and differ from regular topics that the connecting conductors on them are arranged in parallel. Circuit elements are installed on the connecting conductors. If necessary, the conductors can be cut into separate parts or interconnected by jumpers.

And here is a real example of manufacturing a device on such a printed circuit board:

Of course, some skills are required here, in particular the ability to arrange all the details as compactly as possible.

For example, let's assemble a simple amplifier circuit, like this:

C1, C2 - EM or "Tesla": C3 - IT-1; R1 - variable resistor with switch; R2 - ULM or MLT - 0.25; loudspeaker - 0.2 GD-1 with a voice coil resistance of 28 ohms.

Let's take a look at how the board for mounting the amplifier is being prepared. First, a rectangular plate of predetermined dimensions is cut out from a piece of foil-coated getinax or textolite. Then, with a caliper, the foil is divided into seven equal strips, between which the foil is cut (as in the figure)

After that, holes are marked and drilled from the side of the foil layer. The drill should have a diameter of 1.0-1.2 mm. Where necessary, cuts are made with a sharp scalpel

Circuit details and connecting jumpers (single-core tinned wire with a diameter of 0.5-1.0 mm) between individual strips are installed on the reverse side of the board

You need to solder the circuit with a small soldering iron, and its tip should not be wider than the foil strip. When soldering, make sure that the solder does not spread and does not close adjacent areas.

Printed-parallel boards can be made without foil getinaks. To do this, glue BF-2 strips of thin copper foil on any insulating material (textolite, getinaks. plexiglass, etc.) 1.5-2.0 mm thick and heat the plates at a temperature of 100-120 ° for two hours .

Note.
Although the source of this material was published back in 1967, this topic has not lost its relevance. Moreover, in our time, printed circuit boards are produced that do not require soldering. If you are interested in what they look like and where you can buy them, then I recommend to look here

Etching is a process in which part of the metal is removed from the surface by chemical means. This method is used for the final processing of the part, when preparing the workpiece before applying the coating (galvanic), as well as for creating all kinds of drawings, ornaments and inscriptions.

The essence of the method

Metal etching involves careful surface treatment. A protective coating is applied to the product, which is washed in place of the pattern. Then either acids or an electrolyte bath are used. Unprotected places are destroyed. The longer the exposure time, the deeper the etching of metals occurs. The drawing becomes more expressive and clear. There are various ways to obtain an engraving (inscription): the image itself or the background can be etched directly. Often these processes are combined. Multi-layer etching is also used.

Etching types

Depending on the substance used to destroy the surface of the material, the following etching methods are distinguished.

1. Chemical method (it is also called liquid). In this case, special solutions based on acids are used. Thus, ornaments and inscriptions are applied to the alloys.

2. Electrochemical etching of metal - involves the use of an electrolyte bath. It is filled with a special solution. Lead salts are also often used to prevent overetching. This method has a number of advantages. Firstly, the drawing is clearer, and the time required to complete the process is significantly reduced. In addition, such metal processing is economical: the volume of acid used is much less than with the first method. Another undoubted advantage is the absence of harmful gases (mordant does not contain caustic acids).

3. There is also an ion-plasma method (so-called dry). In this case, the surface is damaged minimally. This method is used in microelectronics.

Steel Pickling

Basically, this treatment is used to remove scale and various oxides. This procedure requires careful adherence to technology, since overetching of the base metal is undesirable. In the process, both a chemical method and electrolyte baths are used. Hydrochloric and sulfuric acids are used to prepare solutions. All parts require careful degreasing of the surface. Even a small fingerprint can ruin the workpiece. As a protective coating, varnish based on rosin, turpentine, and tar is used. However, it is worth remembering that the components are flammable substances, so the preparation of varnish requires great concentration and caution. After the metal processing is completed, the etching process itself takes place directly. Upon completion, the part must be cleaned of varnish.

Picklings used for steel

Very often, a solution of nitric acid is used to pickle steel. Also used is salt, tartar (with small additions of nitrogen). Hard steel grades are pickled with a mixture of nitric and acetic acids. Glyphogen is a special liquid based on water, nitric acid and alcohol. The surface is treated with this composition for several minutes. Then washed (solution of ethyl alcohol in purified water), dried quickly. This is a pre-treatment. Only after such manipulations are the workpieces placed in the pickling solution. Cast iron is well pickled in a solution of sulfuric acid.

Pickling of non-ferrous metals

Copper and alloys based on it are pickled with sulfuric, hydrochloric, phosphoric or nitric acids. The process is accelerated by solutions of chromates or nitrates. The first stage is the removal of scale, then the brass is directly etched. Aluminum (and its alloys) are etched in a solution of caustic alkali. For casting alloys, nitric and hydrofluoric acids are used. Spot-welded blanks are treated with phosphoric acid. Titanium alloys are also pickled in two stages. First - in caustic alkali, then in a solution of sulfuric, hydrofluoric, nitric acids. Titanium etching is used to remove the oxide film before electroplating. Molybdenum is treated with a solution based on sodium hydroxide and hydrogen peroxide. In addition, etching of metals (such as nickel, tungsten, for example) is carried out using water, hydrogen peroxide and formic acid.

There are several ways to etch boards. In the first case, water and ferric chloride are used. It can also be made independently. To do this, iron filings are dissolved in hydrochloric acid. The mixture is kept for some time. Also, etching of printed circuit boards is carried out using nitric acid. The whole process takes about 10 minutes. At the end of it, the board must be thoroughly wiped with baking soda, as it perfectly neutralizes the remnants of a caustic substance. Another etching composition includes sulfuric acid, water, hydrogen peroxide (in tablets). It takes much more time to etch boards with such a composition: hot water, table salt, blue vitriol. It is worth noting that the temperature of the solution should be at least 40 degrees. Otherwise, etching will take longer. Boards can also be etched using direct current. As dishes for this process, you can use glass, plastic containers (it does not conduct current). Fill the container with edible salt solution. It is he who is the electrolyte. As a cathode, you can take a copper (brass) foil.

Pickling process for other materials

Currently, this type of glass processing, such as etching, is widely used. Vapors of hydrofluoric acid, hydrogen fluoride are used. First, acid polishing of the surface is carried out, then a pattern is applied. After these manipulations, the product is placed in a bath with an etching solution. Then the glass is thoroughly washed and cleaned of the protective coating. As the latter, you can use a mixture based on beeswax, rosin, paraffin. Etching glass with hydrofluoric acid is used to give it a haze. There is also the possibility of color etching. Silver salts give surfaces yellow, red, blue shades, copper salts - green, black, red. To obtain a transparent, shiny pattern, sulfuric acid is added to hydrofluoric acid. If deep etching is required, the process is repeated several times.

Pickling Safety

Metal pickling is a rather unsafe activity that requires a lot of concentration. This is due to work with aggressive materials - acids and their mixtures. First of all, for this process it is necessary to correctly choose a room with good ventilation. Ideal when pickling will use a fume hood. If one is not available, then it is necessary to take care of a respirator to avoid inhalation of harmful fumes. When working with acids, rubber gloves and an apron should be worn. Should always be on hand baking soda, which - if necessary - can neutralize the action of the acid. All pickling solutions must be stored in special containers (glass or plastic). Do not forget about the stickers, which will indicate the composition of the mixture, the date of preparation. There is one more rule: jars of acids should not be placed on high shelves. Their fall from a height is fraught with serious consequences. Artistic metal etching is not complete without the use of nitric acid, which is quite caustic. In addition, in some mixtures it can be explosive. Most often, nitric acid is used for sterling silver. Etching solutions are prepared by mixing acids with water. It is also worth remembering that in all cases the acid is added to the water, and not vice versa.

Metal etching sometimes replaces casting and engraving, it makes the whole process much easier. You can get a picture as a concave - embossed, and a convex - bas-relief. Metal etching at home can be chemical and galvanic. The first option is more toxic when used at home, so for starters we will use the second, it is also called electrochemical.

Equipment

You need to take a power supply or a transformer that can output from 4 to 7 V. In addition, you will need a dielectric bath, it must contain the necessary part and a second metal object that is connected to the anode.

To carry out the etching of the pattern on the metal, it is necessary to use it as iron sulphate. If a drawing is needed on a copper or brass surface, then you can also use it. The main thing is that the water be distilled.

Preparing the part for etching

In order for the etching to be uniform and in the right places, the part must be cleaned of dirt and degreased. For more convenient work, the part is soldered with tin copper wire, for it will be convenient to hold the object. To clean the surface, you need to lower the object to be converted into 10% sodium hydroxide, the temperature of which is 50 ° C, then into a 15% sulfuric acid solution and hold it there for two minutes, then rinse it in hot water. When the procedure is completed, the surfaces of the object will be completely cleaned, and of course, you cannot touch them with your hands.

Electrochemical etching of metal

We need to protect the places that shouldn't be pickled. To do this, it is necessary to apply a special mastic to these areas of the surface. It is made from three shares of wax and two - rosin, they are melted in a tin, stirring. After everything turns into a homogeneous mass, it is allowed to cool and divided into fragments. Each of them is placed in gauze, so that when pressed, as much mastic as necessary can seep through it. After that, the workpiece, which we will pickle, heats up. Now we take the created mixture, which was placed in gauze, and rub the surface with an even layer.

After cooling, the mastic becomes solid. From above it is covered with light water-soluble paint. It can be watercolor or gouache white. After that, the coating should dry. Then you can apply a drawing, it will hold well on the paint. It can be drawn with a pencil or translated through carbon paper. Then this contour must be scratched with a needle to the metal itself.

Now the etching of the metal by electrolysis begins, we connect one rod to the anode - plus, the other to the cathode - minus. To the first we connect the part on which the image will be applied, to the second any steel plate. After that, the process of etching the metal begins where the image was scratched.

If you need to create a multi-level drawing, everything is done in the same way as described above. Only the contours are checked every time, and when the smallest of them are etched to the prescribed depth, the part is removed and painted over with heated mastic using a brush. When it hardens, everything is repeated again until the next level of the drawing. In the process, an image is gradually created.

In this way, the metal is etched at home, after which the surface is washed with turpentine, and then polished, giving the product a finished look.

Etching chemical

Now let's look at how to create a pattern on a metal surface without the use of electrical appliances. To do this, we need chemicals that are freely sold in hardware stores. So, let's begin. For etching we need:

• "White Spirit";
• paint that does not dissolve in White Spirit;
• acetone;
• resin that is used to cover roofs;
• table salt;
• copper sulfate.

Part cleaning

To begin with, the part where the image is planned is cleaned with fine sandpaper and degreased. When the surface is ready, you need a place where the pattern will be applied, sealed with adhesive tape or something similar. After that, the rest of the surface, where chemical etching should not affect the metal, is painted over with paint. It can be of any color, as long as it is resistant to White Spirit.

When the paint dries, you can remove the adhesive tape. Beneath it is pure metal, ready to be painted on. Now on this "mini-canvas" you need to apply an image. It is made using resin, which is dissolved in White Spirit until it becomes liquid, like paint. She draws the desired image with a brush. What is good about such improvised paint is that if something does not work out in the drawing, then it will be possible to remove it by moistening a rag or cotton swab in White Spirit. If the drawing has very small details that did not turn out well with a brush, they can be corrected with a needle, scraping off the excess after drying.

In this way, you can etch a knife, keys, in general, any metal object. Now that the drawing is completely ready, you can proceed to the etching itself.

pickling solution

We need a liter of water, in which we need to dissolve 100 g of copper sulfate, and then add salt. It must be poured until it ceases to dissolve. The resulting mixture will have a blue color. However, after a metal object is immersed in it, the color will begin to change to green.

So, let's load the item. The chemical process starts immediately. In all this production, no substances harmful to health are emitted, so such metal etching at home is safe.

Actions in a chemical reaction

During the reaction, a plaque is formed, which will become more and more. It slows down the whole process, so you need to periodically wash it off with water. You should not do this with the help of various brushes, brushes and other tools, because you can damage the paint. But she seems to be holding the whole drawing, and it will be a shame if, by etching a knife, for example, you inadvertently damage the drawing on it. This is a very delicate work that requires a firm hand and patience.

The depth of the pattern directly depends on the time during which the metal will remain in solution. There are no exact criteria, so each master must himself observe the course of a chemical reaction. And only after doing this several times, it will be possible to say with confidence how much time is needed for the manifestation of the desired pattern to the intended depth.

Advantages and disadvantages of electrochemical and chemical etching

The advantages of electrochemical metal etching at home include the fact that the pattern being created is clearer, this is clearly visible if you look at it with magnification. However, the downside is that this method requires an electrical device, which may not be for everyone.

The advantages of chemical etching include the fact that everything you need can be bought at a hardware store. These ingredients are cheap, and, most importantly, you don’t need to look somewhere for a power supply or other devices capable of delivering from 4 to 7 V. However, the imperfect edges of the pattern are a minus.

Etching is a method of reproducing drawings, ornaments, inscriptions, etc. using chemical means. on the surface of metal objects.

Etching is done two ways: you can cover all the lines and surfaces of the pattern with a substance that is affected by the mordant.

And you can, on the contrary, protect all gaps from the action of acids, leaving the lines and surfaces of the pattern free.

If you then cover the entire surface with acid, then in the first case the drawing will turn out to be slightly embossed, in the second - the drawing will come out in-depth.

As simple as the etching operation at first glance, beginners often fail, especially when etching thin and complex patterns.

Surface cleaning

Before applying a protective coating, the surface to be treated should be thoroughly cleaned of a thin coating of rust, grease and other dirt. Fat adhering to the surface can be removed by washing in alcohol or gasoline, calcining, or, finally, boiling in a solution of soda or caustic sodium.

The object, cleaned of dirt and grease, is immersed in a 10% solution of sulfuric acid and left in it until the dark coating of rust disappears.

After that, the surface to be treated can be polished if the shape of the object allows and its purpose does not contradict this operation. But such pre-polishing is not required.

The cleaned surface should not be touched with bare fingers, since there is always a greater or lesser amount of fatty substance on them, and the mordant does not affect the fat.

When the surface to be etched is clean enough to have a fresh metallic sheen, the protective coating is applied.

Protective covering

A good coating can be prepared as follows: melt 1 part of asphalt and 2 parts of mastic, mix the mixture and add 2 parts of white wax to it.

Upon cooling, this composition is formed into balls and cones, which are first wrapped in a cloth made of thin dense fabric, and on top - in dry taffeta.

The composition is applied to the surface as follows: the workpiece is heated and, gently pressing on the surface, they are driven evenly over it with a mass wrapped in taffeta; at the same time, the composition melts and seeps through the rag, covering the rubbed surface with a thin layer.

When this coating hardens, it is covered with a thin layer of white lead, finely ground and dissolved in a solution of gum arabic.

Transferring a picture

Then, using blue paper, the required drawing or inscription is transferred to a white surface. All places that need to be etched are scraped to the surface of the metal. A thin and sharp engraving needle can reproduce even the finest shading of a picture.

If you want to etch a simple figure or an inscription, then the protective coating can be diluted with some liquid, such as turpentine, to the consistency of thick oil paint. On such a coating, it is possible to reproduce the required drawing by hand with a needle or even a steel pen.

When applying a protective coating, it is necessary to ensure that the metal surface is completely dry, otherwise the coating will not stick well in places, and the acid can then penetrate to the metal and pickle the places that should remain intact.

Pickle Recipe

Mordant for copper, brass, bronze and silver products the following mixture is used: 3 parts of a saturated aqueous solution of copper nitrate and 1 part of a saturated acetic solution of ammonia.

Etching

The object to be etched is lowered into a glazed clay cuvette (bath), into which the appropriate solvent is poured.

If the surface to be treated is flat, then you can set it in a horizontal position, fashion a finger-thick wax rim around the edges, and pour the appropriate acid into the flat cuvette thus obtained.

When the etching is considered complete, the object is rinsed in clean water, and the protective coating is removed by heating or washed off with turpentine.

If a certain amount of etchant remains in the recesses, then over time it will corrode the metal surface in places deeper than required. To avoid this, the washed object is placed for several minutes in lime water, which neutralizes the acid residue.