What is the PCB plug hole process

Under the premise that electronic products tend to be multi-functional and complex, the line spacing of PCB boards is getting smaller and smaller, and the speed of signal transmission is relatively improved. High-density integration (HDI) technology can make the design of end products more miniaturized. Compared with conventional PCB technology, HDI circuit boards use thinner line width/spacing (≤ 2/2 mil), smaller vias (<0.15mm) and pads (<0.4 mm), and higher Pad density (>20 pads/cm2). Holes in the disk are often used in HDI boards, and the holes in the disk are required to be full, so the requirements for the holes in the disk are getting higher and higher. Such as: no solder resist ink should enter the hole, causing tin beads to be hidden in the hole. When the PCB is wave soldered, the tin will pass through the component surface from the via hole to cause a short circuit; no oil explosion, causing SMT soldering, etc.

Ink plug hole: The ink plug hole is used for common through holes in the PCB. After the hole is plugged, the surface is ink and will not conduct electricity. Usually, the requirements after plugging the holes: A. It must be fully plugged; B. There should be no redness or false copper exposure; C. It should not be too full and the protrusions should be higher than the pads to be welded next to it (it will affect the SMT installation). paste).

Resin plug hole (POFV): The resin plug hole simply means that after the hole wall is plated with copper, the via hole is filled with epoxy resin, the surface is polished, and then the surface is plated with copper, which is costly.

Blind hole (HDI) inner layer resin plug hole:

For some blind via products, because the thickness of the blind via layer is greater than 0.5mm, the blind via cannot be filled by pressing PP glue, and resin plugging is also required to fill up the blind via to avoid copper-free holes in the blind vias in the subsequent process. question.

The difference between resin plug hole and green oil plug hole:

Before the resin plugging process became popular, PCB manufacturers generally adopted the ink plugging process with a relatively simple process, but the green oil plugging will shrink after curing, which is prone to the problem of air blowing in the air, which cannot meet the user's high plumpness. Require. The resin plugging process uses resin to plug the blind holes and then press them, which perfectly solves the drawbacks caused by the green oil plug holes, and balances the thickness control of the press-fit dielectric layer and the inner layer blind hole filling. contradiction between. Although the resin plugging process is relatively complex in process and high in cost, it has more advantages than ink plugging in terms of fullness and plugging quality.