When solder mask opening in PCB manufacturing, it is generally stipulated that solder mask ink cannot enter through holes. But plug hole requires solder mask ink to enter the hole. Have questions about this?
Answer: solder mask opening (mainly used for surface mount pads and device plug-in holes, mounting holes, test points, etc. At this time, solder mask ink cannot cover the pads and holes, because solder mask ink is a non-conductive substance, if it enters Holes or disks will cause poor welding, poor detectability, etc.)
A. If you want to get the PCB board, all the via pad surfaces, the holes, and other device pads are sprayed with tin (or other surface processes). When you are processing data, the solder mask should be opened.
B. If your PCB board has a high density, the via hole is best to require a plug hole, that is, the via hole arm is filled with solder mask ink, and the surface is also sealed. This reduces the short circuit phenomenon in the pcb assembly process.
C. Of course, the silk screen must be strict. If it is capped onto the disk to be welded, reliability cannot be guaranteed when welding.
3. What is the standard of BGA plug hole? Sometimes plug holes are needed, and sometimes plug holes are not needed?
Answer: Vias that are very close to the pad or dense trace vias (size less than 0.4mm, generally 0.3 / 0.25mm are more common), in order to prevent short circuits, plug holes are required. Vias on the bottom of the BGA: If it is not a test point, plug holes are required to prevent short circuits and Tibetan tin beads. If you want to do it as a test point, you can open the solder mask on the bot side, open a small window on the top side or cover it with green ink. (When the pitch of bga is large, it is recommended to open a small window to deal with the test point, when the pitch is less than 1mm, it is recommended to cover with solder mask ink).
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