PCB Tech - Why do some high-frequency circuit boards need to make resin plug holes

The process of using resin plugs for high-frequency circuit boards is often due to BGA parts, because traditional BGA may make VIA between PAD and PAD to the back of the wiring, but if the BGA is too dense and the VIA cannot go out, you can directly The PAD is drilled and made via to another layer for routing, and then the hole is filled with resin and copper-plated into PAD, which is commonly known as the VIP process (viainpad). If you only do via on the PAD without plugging the hole with resin, It is easy to cause leakage of tin, leading to short circuit on the back and empty soldering on the front.

The process of high-frequency circuit board resin plugging includes drilling, electroplating, plugging, baking, and grinding. After drilling, the hole is plated through, then the resin is plugged and baked, and finally it is polished and smoothed. Because the resin does not contain copper, another layer of copper is needed to turn it into PAD. These processes are done before the original high-frequency circuit board drilling process, that is, the fortress holes are processed first, and then Drill other holes and follow the normal process.

If the plug hole of the high-frequency circuit board is not properly plugged and there are bubbles in the hole, because the bubbles are easy to absorb moisture, the PCB circuit board of the high-frequency circuit board may burst when it passes through the tin furnace, but if the hole is plugged in the process If there are bubbles, the bubbles will squeeze out the resin during baking, resulting in a situation where one side is recessed and the other is protruding. At this time, defective products can be detected, and high-frequency circuit boards with bubbles will not necessarily burst because of the failure of the board. The main reason is moisture, so if the board or board that has just been shipped from the factory has been baked when it is loaded, generally speaking, it will not cause the board to burst.

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