Negative process of PCB circuit board: Generally speaking, it is the tenting process. The liquid used in this process is acid etching negative because after the film is produced, the desired circuit or copper surface is transparent, while the other part is black. After exposure in the circuit process, the transparent part is chemically hardened by the dry film resistance agent under the effect of light. The subsequent development process will wash away the dry film that has not hardened, so in the etching process, only the dry film will be bitten off to wash away part of the copper foil (the black part of the film), while the dry film will remain unwashed to belong to the line we want (the transparent part of the film).
The positive process of PCB circuit board is generally the pattern process we refer to, in which the solution is alkaline etched positive. If viewed from the negative, the desired circuit or copper surface is black, instead of the transparent part. Similarly, after exposure through the circuit process, the transparent part is chemically hardened by the light of the dry film inhibitor. The next development process will take no hardened dry film hedge, followed by a lead-tin plating process, the tin-lead plating in the previous process (development) of dry film hedge copper surface, and then make to membrane action (remove hardened dry film) due to light, and in the next etching process, using alkaline liquid bite off without the protection of a tin-lead copper foil (transparent film), the remaining is the line (black part of the film).
Positive and negative process is according to each company’s process to select,
positive: process is (double panel)
Cutting – drilling – PTH (also called thickening copper plating) – circuit line – second copper plating (graphics) then go SES line (backing down tin film – etching – tun tin)
negative: process is (double panel) cutting – drilling – PTH (also called thickening copper plating) – circuit line (not after 2 copper plating) and then DES line (etch – Stripping)
(1) To distinguish the master film, working film, positive and negative film and the surface of the drug film: films can be divided into master film and working film (sub-film), black film and yellow film, positive film and negative film;
(2) In general the mother for the black film, is mainly used to copy the workpiece), but the workpiece is not only porn, but there is also a black piece of the workpiece, but it is also mainly to do high-precision HDI board or to save money in the disposable used in the production of small-batch PCB, porn is a normal circuit board for ordinary plate and the batch manufacturing.
(3) When differentiating the film surface, the glossy black film is the film surface, while the yellow film is the opposite. Generally, the film surface can be found by scraping the film surface with a pencil or blade.
(4) Note when using yellow tablets: there are two kinds of smooth surface and dumb surface, the second kind of use is easy to appear oil surface indentation.
(5) The negative film on the film line (with copper), the opaque film is a positive film; Positive film is used for graphic electroplating, development of the line, leaving the role of corrosion resistance of the electroplating, mainly plating on lead-tin. The negative film is used for direct etching, and the corrosion resistance after development is the line, which is directly etched with an acid etching solution.
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