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Self-made PCB, your PCB is the master

The corrosive liquid is generally made up of ferric chloride and water. The ferric chloride is a khaki solid and is easy to absorb moisture in the air, so it should be sealed and stored. When preparing the ferric chloride solution, 40% ferric chloride and 60% water are generally used. Of course, more ferric chloride is used, or warm water (not hot water to prevent the paint from falling off) can make the reaction faster Note that ferric chloride is corrosive, it is best not to get it on the skin and clothes (difficult to wash:-(The reaction container uses a cheap plastic basin, just fit the circuit board. The corrosion is from the edge At the beginning, when the unpainted copper foil is corroded, the circuit board should be taken out in time to prevent the paint from peeling off and corroding the useful circuit. At this time, rinse with water, and scrape off the paint with bamboo chips by the way (at this time, the paint It is easier to remove from the liquid.) If it is not easy to scratch, just rinse it with hot water. Then wipe it dry and polish it with sandpaper. The shiny copper foil is exposed, and a printed circuit board is ready. . In order to preserve the results, Bitbaby usually coats the polished circuit board with a rosin solution, which can not only assist the soldering, but also prevent oxidation

circuit board

Overview of the methods of making circuit boards under amateur conditions

       The circuit board is the carrier of the electronic circuit. Any circuit design needs to be mounted on a circuit board to realize its function. And processing circuit boards is the biggest headache for amateur electronics enthusiasts. It is often: the circuit is designed in half a day, but it takes a few days to process the circuit board. Even some very good circuit design ideas have given up the experiment because it takes too much time to process the circuit board and cannot continue to be realized. The webmaster started doing circuit experiments more than 20 years ago. The most confusing thing is to make circuit boards. It can be said that he has tried everything: paint, paraffin, carbon paper, carving knives, and even the nail polish and eyebrow pencils used by MMs. After Dongdu used it, it still couldn't achieve the purpose of making experimental circuit boards with high efficiency and high quality.

        Under amateur conditions, the process of "printing flux, marking, solder mask, etc." can be omitted, and the difficulty lies in the plate-making and printing links. Since only a small amount (one or several pieces) of circuit boards need to be produced, it is obviously uneconomical to adopt formal plate making and printing procedures, so there are various non-printing or sub-printing production methods.

1. Engraving method
        This method is the most direct. Use carbon paper to copy the designed copper foil pattern onto the copper foil surface of the copper clad laminate, and use a special engraving tool polished by a hacksaw blade to directly draw on the copper clad laminate along the edge of the copper foil pattern, cutting as far as possible. Then tear off the copper foil that is not needed outside the graphics, and then plug the component jacks. The key to this method is: the intensity of the depiction is sufficient; the removal of the excess copper foil should start from the edge of the board, and when the operation is good, it can be gradually removed in pieces, and nail scissors can be used to complete this step. Some experimental versions of small circuits are suitable for making with this method.

2. Manual depiction
       It is to directly draw the printed graphics on the copper clad board with a pen, and then perform chemical etching and other steps. This method seems simple, but it is not easy to operate in practice! The current electronic components are small in size, the pin spacing is smaller (on the order of millimeters), and the copper foil traces are also small, and the lines drawn are difficult to modify. To draw such a board depends entirely on your writing skills. . The experience is: the choice of "paint" and paintbrush are both crucial. I myself used red nail polish in a medical syringe to trace the circuit board. The effect is good, but the tip of the needle should be properly processed. Someone also introduced the use of lacquer tablets to dissolve in absolute alcohol and use a duckbill pen to draw. The specific method is as follows :
       Dissolve one part of lacquer tablets (namely shellac, available in chemical raw material stores) in three parts of absolute alcohol, and stir appropriately. Show a certain color, after mixing evenly, it can be used as protective paint to paint circuit boards. First polish the copper-clad board with fine sandpaper, and then use the duckbill pen (or the ink duckbill pen used to draw graphics on the compass) in the drawing instrument to draw. The duckbill pen has a nut to adjust the thickness of the stroke. It is adjustable and can be used to draw a very thin straight line with a ruler and a triangle, and the drawn lines are smooth and uniform, without edge jagged, giving people a smooth and fluent feeling; at the same time, it can also be used in the free space of the circuit board. Write the lines drawn by Chinese characters, English, pinyin or symbols. If it is infiltrated around, the concentration is too small and you can add a little paint; if you can’t draw the pen, it is too thick, and you need to drop a few drops of anhydrous alcohol. . It doesn't matter if you make a mistake, just use a small stick (matchstick) to make a small cotton swab, dipped in a little absolute alcohol, you can easily wipe it off, and then redraw it. Once the circuit board diagram is drawn, it can be corroded in the ferric chloride solution. After the circuit board is corroded, it is also very convenient to remove the paint. Dip a cotton ball with absolute alcohol to wipe off the protective paint, dry it for a while, and then apply pine perfume to use.
       Because the alcohol evaporates quickly, the prepared protective paint should be sealed and stored in a small bottle (such as an ink bottle). Don't forget to cover the bottle cap after use. If the concentration becomes thicker when you use it next time, just add an appropriate amount Anhydrous alcohol is sufficient.

3. Post map method
        There is a "standard pre-cut symbol and tape" available in the electronics store. Common specifications for pre-cut symbols are D373 (0D-2.79, ID-0.79), D266 (0D-2.00, ID-0.80), D237 (OD-3.50, ID-1.50), etc., it is best to buy paper-based materials (black), and plastic-based (red) materials are not used as much as possible. The commonly used specifications of tape are 0.3, 0.9, 1.8, 2.3, 3.7, etc. The units are all millimeters. According to the circuit design layout, select the corresponding symbols and tapes and paste them on the copper foil surface of the copper clad plate. Use a softer hammer, such as smooth rubber, plastic, etc. to hit the sticker to make it fully adhere to the copper foil. Focus on the turning and overlapping of the line. In cold weather, it is best to use a heater to heat the surface to enhance the adhesion effect. After it is posted, the etching process can be carried out.

4. Mimeograph
        Put wax paper on the steel plate, use a pen to engrave the circuit diagram on the wax paper 1:1, and cut the circuit diagram engraved on the wax paper according to the size of the circuit board, and place the cut wax paper on the printed copper plate. Take a small amount of paint and talcum powder to make a suitable thin and thick printing material, dip the printing material with a brush, and evenly apply it to wax paper, repeat it several times, and the circuit can be printed on the printed board. This kind of stereotype can be used repeatedly and is suitable for small batch production. Tip: Use the photoelectric transcription machine to automatically engrave the wax paper of 1:1 size according to the design drawings.

5. Hot-melt plastic film plate making method: for reference.
① Print the circuit board diagram on the printer at a ratio of 1:1 on 80 grams of copy paper. Hand-drawing is also possible, but the bottom paper should be flat.
②Find a fax machine, take out the fax paper from the machine, and replace it with hot-melt plastic film (it is said that it can be bought, and whoever has this product, please contact the webmaster). Put the circuit diagram into the entrance of the fax machine and use the copy button of the fax machine to copy the circuit diagram on the hot-melt plastic film. At this time, the "printed manuscript" of the printed circuit board is ready.
③ Use double-sided tape to smoothly paste the plastic film that has been drawn on the copper-clad board. Pay attention to be flat, not wrinkle, tape paper can not cover the melted part, otherwise it will affect the production effect of the circuit board.
④ Use a paint brush to evenly brush the paint on the plastic film. Note: Do not brush back and forth, only brush in one direction. Otherwise, the plastic film will wrinkle together and the lines on the copper plate will overlap. After the circuit diagrams are all over, remove the plastic film carefully. At this time, a printed circuit board is printed. After it dries, it can be corroded.
        If you want to print multiple pieces, you can make a wooden frame a little larger than the circuit board, and lay the screen on the wooden frame flatly and fix it. Then use double-sided tape to stick the fixed plastic film under the screen. Put the copper-clad board on the table, close the screen frame (the printed image and the copper-clad board should be aligned left and right), use a paint brush to paint in one direction, and remove the screen frame. The printed circuit board is printed. If there is any defect, it can be modified with paint and bamboo.
Pay attention to the above process. When painting, the hand force should be light and heavy. If the paint film is too heavy, the lines will run out of lace, and the lines will break if they are too light. The plastic film must face up.

6. Use pre-coated photosensitive copper clad laminate
        A special copper clad laminate is used. The surface of the copper-platinum layer is pre-coated with a layer of photosensitive material, so it is called "pre-coated photosensitive copper clad laminate" or "photosensitive board". The production method is as follows:
①Single-panel production: Print out a 1:1 black-and-white 720dpi drawing (component side) with a computer-drawn PCB drawing on special inkjet paper. It is also possible to use a laser printer to output the drawing. Take a photosensitive board equivalent to the size of the drawing, and tear off the protective film. Use a glass plate or a plastic transparent plate to press the drawing and the photosensitive PCB tightly, and expose for 5-10 minutes in the sun. Use the attached developer with 1:20 water for development. When the exposed part (unnecessary copper-clad skin) is completely exposed, rinse it with water and it can be corroded with ferric chloride. After the operation is proficient, a trace with an accuracy of 0.1mm can be made!
②The production of double-sided circuit board: the steps refer to the single-sided board, and the double-sided board mainly requires accurate positioning on both sides. Both sides can be exposed separately, but the time should be the same, one side should be protected with black paper during the exposure.

This method is the simplest and most practical method in principle, but the price of commercially available "pre-coated photosensitive copper-clad plates" is relatively high, and it is not easy to buy. Therefore, this method is not yet known to most amateurs.
7. Thermal transfer method
        Use a laser printer to print the designed PCB copper-platinum graphics on the thermal transfer paper, and then stick the thermal transfer paper to the copper-platinum surface of the copper clad laminate, and heat it at an appropriate temperature. The original printed on the transfer paper The graphics (actually carbon powder) will be heated and melted and transferred to the copper-platinum surface to form a corrosion protection layer. This method is simpler than conventional plate-making and printing methods, and most of the circuits are now designed using computer CAD, laser printers are also quite popular, and this process is relatively easy to implement.