Many people think that the pcb board making process is super complICated and difficult to understand, but they can't understand the work needs and have no access to learning. What should we do? Today, let's make it easy for you to get the tips for multi-layer pcb production. Don't think this is too difficult! If you don't believe me, continue to look at the following:
At present, PCB is mostly made by subtracting the excess copper foil on the raw material copper clad plate to form a conductive pattern. The method of subtraction is chEMIcal corrosion, which is the most economical and efficient. Only the chemical corrosion has no differential attack, so it is necessary to protect the required conductive pattern. A layer of anti-corrosion agent should be coated on the
conductive pattern, and then the unprotected copper foil corrosion should be subtracted. In the early days, the anti-corrosive ink was printed in line by screen printing, so it was calLED "printed circuit board". However, as PCB products become more and more sophisticated, the image resolution of printed circuit cannot meet the product requirements, and then photoresist is used as the image analysis material. The photoresist is a kind of photosensitive material, which is sensitive to the light source of a certain wavelength and forms a photochemical reaction with it to form a polymer. After the pattern is selectively exposed with a pattern negative, the unpolymerized photoresist is stripped through the developer (e.g. 1% sodium carbonate solution) to form a pattern protective layer.
In addition, the interlayer conduction function is realized through metallized holes, so the PCB manufacturing process also needs to carry out drilling operations, and metallized electroplating operations for holes, finally realizing interlayer conduction.
1： First, make two holeless double-sided boards:
Blanking (raw material double-sided copper clad laminate) - inner layer pattern making (forming pattern anti-corrosive layer) - inner layer etching (minus excess copper foil)
2： Glue and press the two prepared inner core plates with epoxy resin glass fiber prepreg
Rivet the two inner PCB core plates with the semi cured sheet, then lay a copper foil on both sides of the outer layer and press it under high temperature and high pressure to make it stick together. The key material is the semi curing sheet, which has the same composition as the raw material. It is also epoxy resin glass fiber, but it is not fully cured. It will liquefy at 7-80 ℃. The curing agent is added to it, and it will cross link with the resin at 150 ℃, and then it will no longer be reversible. Through such a semi-solid liquid solid transformation, adhesion and bonding are completed under high pressure.
III. Conventional double-sided board production
Drilling - copper plate electricity (hole metallization) - outer circuit (forming a graphic anti-corrosion layer) - outer etching - solder resistance (printing green oil, text) - surface coating (tin spraying, gold deposition, etc.) - forming (milling forming), complete!