PCB Board Fabrication Process
Some PCB designers especially newbies are unfamiliar with the whole PCB fabrication process. In this article, EPCB will give a brief introduction, and hope it will be useful to you. Here, we will take a simple and normal 4-layer board as example.
We should choose the most suitable PCB material from various PCB brands and parameters. Suppose there are bury holes from L2 to L3, drilling holes on the board is the first step. If not, we can start to make inner circuit. Usually, dry film is used to expose the circuit as per your design, and then etch them out. When the circuit is done, use AOI to check the accuracy of etching. The next is black-oxide, which will make better bonding while laminate.
When all inner layers have finished, lamination will be start in the high temperature and high pressure. The following is the resin scrubbing, and through-holes’ drilling. Since those holes have no copper on wall at first, we must do panel plating.
Now turns to the outer layer circuit. We also use dry film to expose the circuit and then etching. Then paint PCB surface with solder mask ink and print silkscreen. Electrical test, also called open or short test is an essential and important step used to make sure all PCBs can work well as designed. The next is to fabricate surface finish. There are many surface types, like immersion gold or silver or tin, HASL, OSP and more. After that, there are also many process need to go, like Hi-pot test, FQC, FQA, and more.
All in all, the process is very complex because each PCB board has to experience 20+ steps in the whole PCB fabrication process.