PCB (printed circuit board) board composition and industry chain
Methods and steps for making your own PCB board
Circuit board corrosion method:
Corrosive liquid is generally made of ferric chloride and water. Ferric chloride is a yellowish brown solid and is easy to absorb moisture in the air, so it should be sealed and stored. When preparing ferric chloride solution, 40% ferric chloride and 60% water are generally used. Of course, more ferric chloride, or warm water (not hot water, to prevent paint from falling off) can make the reaction faster. Note that ferric chloride is corrosive to a certain extent. It is best not to get it on your skin and clothes (it is difficult to wash:-(The reaction container uses a cheap plastic basin that can hold the circuit board. Corrosion starts from the edge. When the unpainted copper foil is corroded, the circuit board should be removed in time to prevent the useful circuit from being corroded after the paint falls off. Rinse with clean water at this time, and scrape off the paint with bamboo strips or other objects (the paint comes out of the liquid at this time and is easier to remove). If it is not easy to scrape, just rinse it with hot water. Then wipe it dry and use After the sandpaper is polished clean, 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 rosin solution, which can both assist soldering and prevent oxidation
Overview of methods for making circuit boards under amateur conditions
Circuit boards are the carriers of electronic circuits. Any circuit design needs to be installed on a circuit board to realize its function. Processing circuit boards is the most headache for amateur electronics enthusiasts. It is often the case that the circuit is designed in half a day, but it takes several days to process the circuit board. Even some good circuit design ideas are abandoned because processing the circuit board takes too much time and cannot be realized. The webmaster started doing circuit experiments more than 20 years ago, and the most difficult thing was making circuit boards. He tried every possible way: paint, paraffin, carbon paper, carving knives, and even nail polish and eyebrow pencils used by girls, but still could not achieve the goal of efficient and high-quality production of experimental circuit boards.
Later, when I went to the company to do professional design and development, I realized that professional engineers had no idea that there were such difficulties.
They designed the drawings with CAD, printed them out and handed them over to the PCB processing factory, and they could get several processed PCB samples a few days later. Install the parts, debug and modify them, print them again, and send them to the PCB processing factory for processing. After several repetitions, the circuit is ready. They don’t have to consider the various tedious process and production costs in the process of processing circuit boards. The reason why PCB processing factories are not tired of repeatedly processing for these companies for free is that they are very simple and easy to use. The cost of processing experimental circuit boards is obviously not “carry forward the Leifeng spirit”. It is obvious that these processing costs will be allocated to the cost of future mass production.
If you are a small and unknown company or an individual, the cost of processing once may be hundreds of yuan.
Therefore, how to simply, quickly, low-cost and high-quality process experimental circuit boards is a topic worth studying. Now there are many new and good methods, such as: thermal transfer method, pre-coated photosensitive copper plate production method, hot melt plastic film method, etc. This site will collect methods and experiences in this regard, and organize them into articles, which will be published on this site one after another. We also welcome enthusiasts, manufacturers, material and equipment suppliers, etc. to cooperate, or write articles, or provide your products, or cooperate in sales.
As mentioned in the preface, the circuit board is the carrier of the circuit, which we usually call “printed circuit board” with the English abbreviation “PCB”. Regular production of printed circuit boards is naturally related to printing, and the screen printing process is usually used. The basic process is as follows: Design layout → Tracing → Plate exposure (making printing base) → Printing → Chemical corrosion → Cleaning and surface treatment → Printing soldering, logo, solder mask and other layers → Cutting, punching and other mechanical processing → Finished circuit board
For more detailed operation steps, please see the article “Screen printing to make circuit boards and instrument sign panels” collected by this site (in the “Practical basis” column).
Under amateur conditions, the process of “printing soldering, logo, solder mask and other layers” can be omitted, and the difficulty lies in the plate making and printing links. Since only a small number of circuit boards (one or several pieces) need to be made, it is obviously not economical to use regular plate making and printing processes, 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 to the copper foil surface of the copper clad board. Use a special engraving tool made of a hacksaw blade to carve along the edge of the copper foil pattern on the copper clad board. Cut as deep as possible, then tear off the unnecessary copper foil outside the pattern, and then punch the socket of the component. The key to this method is: the carving force must be enough; tear off the excess copper foil from the edge of the board. If the operation is good, it can be gradually torn off in pieces. You can use nail clippers to complete this step. Some small circuit experimental boards are suitable for this method.
2.Manual drawing method
It is to use a pen to directly draw the printed pattern on the copper clad board, and then perform chemical etching and other steps. This method seems simple, but it is not easy to operate in practice! Today’s electronic components are small in size, the pin spacing is smaller (millimeter level), the copper foil routing is also small, and the lines drawn are difficult to modify. To draw such a board well depends entirely on your pen skills. Experience is: the selection of “pigment” and brush is very important. I have used red nail polish in a medical syringe to draw circuit boards, and the effect is good, but the tip of the needle needs to be properly processed; some people also recommend using paint flakes dissolved in anhydrous alcohol and using a duckbill pen to draw, the specific method is as follows:
Dissolve one part of paint flakes (i.e. shellac, available at chemical raw material stores) in three parts of anhydrous alcohol, and stir appropriately. After it is completely dissolved, add a few drops of medical violet solution (gentian violet) to make it present a certain color. After stirring evenly, it can be used as a protective paint to draw circuit boards. First, polish the copper plate with fine sandpaper, and then use the duckbill pen in the drawing instrument (or the ink duckbill pen used to draw graphics on the compass) to draw. The duckbill pen has a nut to adjust the thickness of the stroke. The stroke thickness is adjustable, and you can use a ruler or a triangle ruler to draw very thin straight lines. The lines drawn are smooth and uniform, without edge jagged, giving people a smooth and fluent feeling; at the same time, you can also write Chinese characters, English, pinyin or symbols on the free space of the circuit board. If it soaks around, the concentration is too low, and you can add a little paint flakes; if you can’t drag the pen, it’s too thick, and you need to drop a few drops of anhydrous alcohol. It doesn’t matter if you draw it wrong. Just use a small stick (matchstick) to make a small cotton swab, dip it in a little anhydrous alcohol, and you can easily wipe it off, and then redraw it. Once the circuit board diagram is drawn, it can be corroded in a ferric chloride solution. After the circuit board is corroded, it is also very convenient to remove the paint. Use a cotton ball dipped in anhydrous alcohol to wipe off the protective paint. After drying it slightly, you can apply rosin water and use it.
Because alcohol evaporates quickly, the prepared protective paint should be placed in a small bottle (such as an ink bottle) and sealed for storage. Don’t forget to cover the bottle cap after use. If the concentration is found to be thicker when you use it next time, just add an appropriate amount of anhydrous alcohol.
3.Posting method
Electronic stores sell a kind of “standard pre-cut symbols and tapes”. The common specifications of 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) and other types. It is best to buy paper-based materials (black), and try not to use plastic-based (red) materials. Common specifications of tapes are 0.3, 0.9, 1.8, 2.3, 3.7 and other types. The unit is millimeter. According to the circuit design layout, you can choose 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 points and overlaps of the lines. When it is cold, it is best to use a heater to warm the surface to enhance the adhesion effect. After posting, you can proceed with the corrosion process.
4.Mimeographing method
Put the wax paper on the steel plate, use a pen to carve the circuit diagram on the wax paper at a ratio of 1:1, and cut the circuit diagram engraved on the wax paper according to the size of the circuit board, and put the cut wax paper on the printed copper-clad plate. Take a small amount of paint and talcum powder to make a suitable printing material, dip the printing material with a brush, and evenly apply it to the wax paper. Repeat several times, and the printed board can be printed with the circuit. This stereotype can be used repeatedly and is suitable for small batch production. Tip: Using a photoelectric copier, you can automatically carve a 1:1 size wax paper according to the design drawing.
5.Hot-melt plastic film plate making method: This method is collected from online articles (author NewBlue), and its feasibility has not been verified. It is for reference only.
① Print the circuit board diagram on 80g copy paper at a ratio of 1:1 on the printer. Manual drawing is also possible, but the base paper must be flat.
② Find a fax machine, take out the fax paper in the machine, and replace it with hot-melt plastic film (it is said that it can be bought. If anyone has this product, please contact the webmaster). Put the circuit diagram into the fax machine entrance, and use the copy key 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 stick the plastic film with the drawing flat on the copper-clad board.
Note that it should be flat and not wrinkled. The tape cannot cover the melted part, otherwise it will affect the production effect of the circuit board.
④ Use a paint brush to evenly apply the paint on the plastic film.
Note: You cannot brush back and forth, but can only brush in one direction in sequence, otherwise the plastic film will wrinkle together and the lines on the copper plate will overlap. After the circuit diagram is completely painted, carefully remove the plastic film. At this time, a printed circuit board is printed. After it dries, it can be etched.
If you want to print multiple pieces, you can make a wooden frame that is slightly larger than the circuit board, apply the silk screen flatly on the wooden frame, and fix it. Then use double-sided tape to stick the fixed plastic film under the silk screen. Put the copper plate on the table, close the silk screen frame (the printed diagram and the copper plate should be aligned left and right), use a paint brush to apply the paint in one direction in turn, and remove the mesh frame. The printed circuit board is printed. If there are defects, you can modify them with paint and bamboo strips.
In the above process, it should be noted that when painting, the hand force should be appropriate. If it is too heavy, the paint film will be too thick, and the lines will run lace, and if it is too light, the lines will be broken. The plastic film must be facing up.
6.Use pre-coated photosensitive copper-clad board
Use a special copper-clad board, the copper-platinum layer surface is pre-coated with a layer of photosensitive material, so it is called “pre-coated photosensitive copper-clad board”, also called “photosensitive board”. The production method is as follows:
① Production of single-sided board: Print out 1:1 black and white 720dpi drawings (component side) with special inkjet paper for PCB drawings drawn by computer. It is also OK to use laser printer to output drawings. Take a photosensitive board of the same size as the drawing and tear off the protective film. Press the drawing and the photosensitive PCB board with a glass plate or a plastic transparent plate and expose them to the sun for 5-10 minutes. Use the attached developer 1:20 with water for development. When the exposed part (unnecessary copper foil) is completely exposed, rinse it with water and then use ferric chloride for corrosion. After proficiency in operation, you can make a trace with an accuracy of 0.1mm!
② Production of double-sided circuit board: The steps refer to the single-sided board. The main thing for double-sided board is to accurately position both sides. Both sides can be exposed separately, but the time must be consistent. When one side is exposed, the other side must be protected with black paper.
This method is the simplest and most practical method in principle, but the “pre-coated photosensitive copper-clad board” on the market is relatively expensive and not easy to buy. Therefore, this method is not known by most amateurs. Manufacturers are welcome to contact this site for cooperative promotion.
7.Thermal transfer method
Use a laser printer to print the designed PCB copper-platinum graphics on thermal transfer paper, and then press the thermal transfer paper against the copper-platinum surface of the copper-clad board. Heat it at an appropriate temperature, and the graphics originally printed on the transfer paper (actually carbon powder) will melt due to the heat and transfer to the copper-platinum surface to form a corrosion protection layer. This method is simpler than conventional platemaking and printing methods, and most circuits are now designed using computer CAD, and laser printers are also quite popular, so this process is relatively easy to implement.
