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In double-sided circuit boards and PCB multilayer circuit boards, in order to connect the printed wires between the various layers of circuit boards, it is necessary to drill a common hole, that is, a via hole, at the intersection of the connected wires of each layer. In the process of making PCB multilayer circuit boards, the via holes must be plugged. One method of via hole processing is via hole plugging process.
Through hole plug oil refers to the use of ink to make the plug hole inside the hole of the through hole,and the quality and density of the plug hole are pursued. So what is the inspection standard for the treatment of the via plug oil?The first standard is to be opaque, and the ink must be covered and blocked.The second criterion is that the orifice must not show yellowing, and it must be free of tin.
The via plug oil process is an important supplement to the via cover oil.Usually high-quality PCB multilayer circuit boards require the production of via plug oil, especially for vias like BGA. The requirements are relatively high.The via plugging oil is to plug the ink into the full hole first to block the via hole,so that the ink on the solder mask can not flow into the via hole, so as to achieve the purpose of preventing yellowing of the via hole.The smaller the via hole of the circuit board is,the easier it is to plug.The via hole that needs to be plugged should not be too large, the maximum is 0.5mm.If the hole exceeds 0.5mm,it is recommended to cover the via hole.
In addition,for those with relatively high process requirements,if there is too little cover oil or a yellowish phenomenon,it can be changed to via hole plug oil in the later stage. Engineers need to pay attention to the following matters when docking the via plugging process with the PCB multilayer circuit board factory:
1.The attributes of the vias when placing an order must be the same as the attributes of the file,which can shorten the time for mutual confirmation with PCB multilayer circuit board manufacturers.
2.If a window is required, the corresponding solder mask must be clearly drawn.
3.If the circuit board has a large number of pads that need to be soldered later,it is recommended to make a via cover oil, which can reduce the frequency of short circuits.
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