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The difference between positive and negative PCB boards

Views:29     Author:Site Editor     Publish Time: 2018-12-20      Origin:Site Inquire

Negative film board: Generally speaking, we are using the tenting process. The liquid used is acid etching negative film. Because the film or copper surface is transparent after the film is made, the unnecessary part is black. After the line process exposure, the transparent part is chemically hardened due to the light of the dry film resist. The subsequent development process will wash away the dry film without hardening, so only the dry film is washed away during the etching process. The copper foil (the black part of the film), while leaving the dry film unwashed is the line we want (the transparent part of the film).


The positive film of the circuit board: generally the pattern process we are talking about, the liquid used is an alkaline etching positive film. If the negative film is used, the desired line or copper surface is black, and the part is transparent, and the same is true. After exposure by the line process, the transparent part is chemically hardened by the dry film resist by the light, and the subsequent development process will wash away the dry film without hardening, followed by the tin-plated lead process, and the tin-lead is plated. The previous process (developing) the copper surface washed away by the dry film, and then the action of removing the film (removing the dry film hardened by the light), and in the next process etching, the alkaline potion is used to bite off the tin-lead protection. Copper foil (the transparent part of the film), the rest is the line we want (the black part of the film).


Positive and negative films are actually selected according to the company's process, the positive film: the process is (double panel) cutting - drilling - PTH (primary plating is also called thick copper) - line - two copper (graphic plating) and then take SES Line (de-filming-etching-removing tin) negative film: the process is (double-panel) cutting-drilling-PTH (primary plating is also called thickening copper)-line (without two-copper pattern plating) and then walking the DES line (etching - peeling off).


1.distinguish between the mother film, the working piece, the positive and negative film and the film surface of the film (film): the film has the mother piece and the working piece (sub piece), the black piece and the yellow piece, the positive piece and the negative piece; 

2.in general, the mother piece It is also known as silver salt tablets, which is mainly used to copy work pieces (yellow pieces are also called diazo tablets), but the work pieces are not necessarily only yellow pieces, but also black pieces are used as work pieces, mainly for high precision HDI. The board is used in the production of disposable small-volume circuit boards for the purpose of cost saving, and the yellow sheets are used for the manufacture of ordinary boards for ordinary boards and batches; 3.When the film surface is distinguished, the black film is the film, and the yellow film is the opposite. Generally, the film can be seen on the film by a scraping pen or a blade. (Master: Orthodox medicinal noodles, sub-tablets: Orthographic anti-drug);

4.Yellow tablets when using Note: There are two kinds of glossy and matte, and the second type is prone to oil surface indentation;

5.Film line on the film line (with copper), opaque to positive film; positive film is used for pattern plating, the circuit is developed, leaving the effect of corrosion-resistant plating, mainly coated with lead-tin . The negative film is used for direct etching, and the resist is left as a line after development, and is directly etched with an acidic etching solution.


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