PCB circuit board negative film: generally we talk about the tenting process. The chemical solution used is an acid etching negative film because after the film is made, the required circuit or copper surface is transparent, and the unneeded part is black. After the circuit process is exposed, the transparent part is chemically hardened due to the dry film resist being exposed to light. The subsequent development process will wash away the unhardened dry film, so only the dry film washed out part is bitten during the etching process. The copper foil (the black part of the negative film), while leaving the dry film not washed off belongs to the circuit we want (the transparent part of the negative film)

 

The positive film of the PCB circuit board: generally we talk about the pattern process. The yao liquid used is an alkaline etching positive film. If you look at the negative film, the required circuit or copper surface is black, and the other part is transparent. Similarly, after exposure through the circuit process, the transparent part is chemically hardened by the dry film resist being exposed to light. The next development process will wash off the unhardened dry film, followed by the tin-lead plating process to remove the tin-lead It is plated on the copper surface washed away by the dry film of the previous process (development), and then the film is removed (removing the dry film hardened by light), and in the next process of etching, use alkaline yao water to bite off no tin Lead-protected copper foil (the transparent part of the negative), and the rest is the circuit we want (the black part of the negative)

 

Positive film and negative film are actually selected according to the process of each circuit board factory. Positive film: The process is (double-sided circuit board) cutting-drilling-PTH (one-time plating is also called thickened copper)-circuit-two copper (graphic plating) ) Then take the SES line (removal film-etching-stripping tin) negative film: the process is (double-sided) cutting-drilling-PTH (one-time plating is also called thickened copper)-line (without two copper pattern plating) and then go DES line (etching-film removal)