Negative film of PCB circuit board: Generally, it is the tenting process we are talking about. The chemical solution used in it is acid etching negative film because after the negative film is produced, the required lines or copper surfaces are transparent, while the unnecessary parts are black. After the exposure of the circuit process, the transparent part will be chemically hardened due to the dry film resist being exposed to light. The next developing process will wash away the unhardened dry film, so only the washed out part of the dry film will be bitten in the etching process. The copper foil (the black part of the negative), and the remaining dry film is washed off, which belongs to the circuit we want (the transparent part of the negative)
Positive film of PCB circuit board: Generally, it is the pattern process we are talking about. The yao liquid used in it is alkaline etching positive film. If you look at the negative film, the desired circuit or copper surface is black, while the unnecessary part is transparent. Similarly, after the exposure of the circuit process, the transparent part will be chemically hardened by the dry film resist under the light, and the next development process will wash away the unhardened dry film, followed by the tin-lead plating process to plate the tin-lead on the The copper surface washed away by the dry film of the previous process (development) is then removed from the film (removing the dry film hardened by light), and in the next process of etching, the copper surface without tin-lead protection is bitten off with alkaline yao water. Copper foil (the transparent part of the negative), and the rest is the circuit we want (the black part of the negative)
The positive film and the negative film are actually select according to the process of each circuit board factory. The positive film: the process is (double-sided circuit board) material cutting-drilling-PTH (primary electroplating is also called thickened copper)-line-two copper (graphic plating ) and then take the SES line (removal-etching-tinning) negative film: the process is (double-sided) material cutting-drilling-PTH (primary electroplating is also called thickened copper) line (without secondary copper pattern electroplating) and then DES Line (etching-removing film)
① Distinguish the master film, working film, positive and negative film and film side of film (negative film): film has master film and working film (child film), black film and pornographic film, positive film and negative film;
② When the yao film surface is distinguished, the glossy side of the black film is the medicated film, while the yellow film is the opposite. Generally, you can scrape the film with a scraper or a blade to see which side is the medicated film. (master piece: orthographic positive medicinal noodles, sub-chip: orthographic anti-medicinal noodles);
③ Generally speaking, the master film is black film, also known as silver salt film, which is mainly used to copy the working film (yellow film is also called diazo film), but the working film does not necessarily only have pornographic film, and there are also black film as working film. It is used to make high-precision HDI boards or to save expenses in the production of one-off small batches of circuit boards. Yellow film is used in the manufacture of ordinary PCB circuit boards and ordinary circuit boards in batches;
④Pay attention when using pornography: There are two types of glossy and matte surfaces, and the second type is prone to oil surface indentations when used;
⑤ The transparent negative film on the film circuit (with copper), the opaque film is the positive film; the positive film is used for graphic electroplating, the circuit is developed, and the role of anti-corrosion electroplating is left, mainly lead-tin plating . The negative film is used for direct etching, and the resist left after development is the circuit, which is directly etched with acid etching solution.
