What is the difference between PCB positive film and negative film? —PCB Negative Film Output Process

by:A-TECH      2021-03-13
1. The difference between PCB positive film and negative film: PCB positive film and negative film are manufacturing processes with opposite final results. The effect of PCB positive film: wherever lines are drawn, the copper on the printed board is retained, and where there are no lines, the copper is removed. The signal layer such as the top layer, the bottom layer... is the positive film. The effect of PCB negative film: wherever lines are drawn, the copper on the printed board is removed, and where there are no lines, the copper on the printed board is retained. The Internal Planes layer (internal power/ground plane) (referred to as the internal electric plane) is used to lay out the power and ground wires. The traces or other objects placed on these layers are copper-free areas, that is, the working layer is negative. 2. What are the differences between PCB positive and negative output processes? Negative film: generally we talk about the tenting process. The chemical solution used is acid etching negative film because after the film is made, the required circuit or copper surface is transparent, and the undesired part is black or brown. After the process is exposed, the transparent part is chemically cured by the dry film resist being exposed to light. The subsequent development process will wash away the uncured dry film, so only the part of the dry film that has been washed away will be etched during the etching process. Copper foil (black or brown part of the negative film), but the dry film is not washed off, which belongs to the circuit we want (the transparent part of the negative film). After the film is removed, the circuit we need is left. In this process The middle membrane must cover the holes, and its exposure requirements and the requirements for the membrane are slightly higher, but the manufacturing process is faster. Positive film: Generally we talk about the pattern process. The chemical solution used is alkaline etching positive film. If you look at the negative film, the required circuit or copper surface is black or brown, and the other parts are transparent. The same goes through After the circuit process is exposed, the transparent part is chemically hardened by the dry film resist being exposed to light. The next developing process will wash off the unhardened dry film, followed by the tin-lead plating process, where tin and lead are plated in front One process (developing) on u200bu200bthe copper surface washed away by the dry film, and then remove the film (remove the dry film hardened by light), and in the next process of etching, use alkaline solution to bite off the copper that is not protected by tin and lead Foil (the transparent part of the negative), and the rest is the circuit we want (the black or brown part of the negative). 3. What are the advantages of PCB positive film, and which occasions are it mainly used for? Negative film is used to reduce the size of the file and reduce the amount of calculation. Where there is copper, it is not displayed, and where there is no copper, it is displayed. This can significantly reduce the amount of data and the burden of computer display in the ground power layer. However, the current computer configuration is no longer a problem for this point of work. I think it is not recommended to use negative films because it is prone to errors. If the pad is not designed, it may be short-circuited or something. There are many ways to split the power source if it is convenient. The positive film can also be easily split by other methods. It is not necessary to use the negative film. The above is the PCB negative film output process-the difference between PCB positive film and negative film, so have you learned it now?
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