what is the difference of pcb negative and positive

1, the difference between PCB positive and negative:

PCB positives and negatives are the manufacturing processes where the final effect is reversed.

The effect of the PCB positive film: Wherever the line is drawn, the copper of the printing plate is retained, and where the line is not drawn, the copper is removed. For example, the signal layer of the top layer, the bottom layer... Is a positive film.

The effect of PCB negatives: Wherever the line is drawn, the copper in the printed board is removed, and where the line is not drawn, the copper is retained instead. The Internal Planes layer (internal power/ground plane) (referred to as inner layer) is used to lay out the power and ground wires. The traces or other objects placed on these levels are copper-free areas, ie the working layer is negative.

    2. What are the differences between the PCB positive and negative output processes?

Negative film: generally we talk about the tenting process, which uses an acidic etching solution

Negative film is because the film or copper surface is transparent after the film is made. The unnecessary part is black or brown. After exposure by the circuit process, the transparent part is chemically affected by the dry film resist. Harden, the next development process will wash away the uncured dry film, then only bite the dry film in the etching process to remove part of the copper foil (the black or brown part of the film), but the dry film is not retained Wash off the lines we want (the transparent part of the film), and leave the film we need after removing the film. In this process, the film should cover the hole, and the exposure requirements and the requirements on the film are slightly higher. Some, but its manufacturing process is fast.

Positive film: generally we are talking about the pattern process, the use of the solution is alkaline etching

If the positive film is viewed from the film, the desired circuit or copper surface is black or brown, and not necessarily transparent. Similarly, after the exposure of the circuit process, the transparent portion is chemically affected by the dry film resist exposed to light. Hardening, the next development process will be washed out of the dry film is not hardened, followed by tin lead plating process, the tin lead plated on the previous process (developing) dry film washed off the copper surface, and then remove the film Action (removal of dry film hardened by light), and in the next process etching, bite off the tin-lead-free copper foil (the transparent part of the film) with alkaline solution, and the rest is the line we want (negative film Black or brown part).

    3, What are the advantages of PCB positive film, mainly used in what occasion?

Negative film is used to reduce the size of the document to reduce the amount of calculation. There is no copper display, no copper display. This can significantly reduce the amount of data and computer display burden in the stratum power layer. However, the current computer configuration is no exception for this workload. I do not think it is recommended to use a negative film and it is easy to make mistakes. The pad is not designed to have a short circuit or something.

There are many ways to split the power supply conveniently. Positive power can also be easily divided by other methods. There is no need to use a negative film.