However, in traditional amateur production, printed boards can only be made by coating copper plates with corrosive liquid. In recent years, the introduction of new technologies such as universal test board and photosensitive circuit board has liberated the vast number of electronic enthusiasts and electronic product developers. Coupled with the popularity of PC, it is not difficult to design circuits with CAD software and automatically generate PCB. It is more convenient to print directly on film with photosensitive circuit board as printing board. The author studied ORCAD software in the school curriculum, and designed a typical application circuit of 803 1 single chip microcomputer with it, which felt really good. Teachers are not allowed to use ORCAD's automatic wiring function. The manual wiring of the author of that picture is beautiful, and the corners of the wiring are smooth transition. Fully considering this design, the printed board is more solid, which makes the teacher think it is automatic wiring. Unfortunately, there was no printer to print PCB at that time. PROTEL is well known to the vast number of electronic enthusiasts, but unfortunately the author has not studied it in depth. Generally, electronic circuits are not complicated, and for an old hand, a printed circuit board can be designed with his brain. Let's talk about the traditional manufacturing methods of printed circuit boards. First of all, the printed circuit board diagram should be designed on paper according to the circuit schematic diagram. The correct connection between components is very important, and attention should be paid to the size, arrangement position and interference of components. I will write an article on how to design printed boards in the future. After the design is completed, it is necessary to proofread the schematic diagram repeatedly, find out the physical components and put them in their respective positions, and adjust the hole spacing and wiring. Pay attention to the front and back. Sometimes you accidentally design the back. You can trace the original picture on carbon paper, and then there will be what you need on the back of the paper. The author's method of making PCB is to cut out the design drawing of 1: 1, stick it on the copper surface of single-sided copper clad plate with transparent glue, and then knock it with a punch at the place where drilling is needed to form a concave point, so that drilling with a small electric drill will not slip. Then drill holes with a self-made small electric drill (modified from the motor of the tape recorder), tear off the drawings after all drilling, and draw lines directly with a brush dipped in paint. Because of the positioning of the holes, it is not difficult to draw, just remember that the holes are connected together. Generally speaking, for uncomplicated circuits, it is very fast to make circuit boards in this way (even carbon paper is saved:-). If the circuit is complicated, you can put a piece of carbon paper between the drawing and the copper clad laminate, then draw the printed board drawing, draw the hole deeper, and then draw the circuit with a brush dipped in paint. If there is no paint, you can use a good quality marker pen to trace the lines, or you can use correction fluid to trace the lines, but the circuit board traced by correction fluid is not very beautiful, so it needs to be corrected with the same width after drying. Nail polish is fine. It dries faster and is better than correction fluid. Pay attention to keep the distance between lines when tracing lines, and enclose the holes for welding. The paint takes a long time to dry. When the paint is dry, it can be put into corrosive liquid. Corrosive liquids are generally made of ferric chloride and water. Ferric chloride is a khaki solid, which absorbs water easily in the air and should be sealed and preserved. When preparing ferric trichloride solution, 40% ferric trichloride and 60% water are generally used, of course, ferric trichloride is more, or warm water (not hot water to prevent paint from falling off) can make the reaction speed faster. Note that ferric trichloride is corrosive to a certain extent, and it is best not to get it on the skin or clothes (it is difficult to wash:-(The reaction container is made of cheap plastic pots, as long as it can hold the circuit board. Corrosion starts at the edge. When the unpainted copper foil is corroded, the circuit board should be taken out in time to prevent the useful circuit from being corroded after the paint falls off. At this time, rinse with clear water, and scrape off the paint surface with bamboo chips and other things (at this time, the paint surface comes out of the liquid and is easier to remove). If it doesn't shave well, just rinse it with hot water. Then dry it and polish it with sandpaper, and the shiny copper foil will be exposed, and a printed circuit board will be finished. In order to preserve the results, the author usually applies rosin solution on the polished circuit board, which can not only help welding, but also prevent oxidation. The following is a sample made by the author: