How does a personal project process the VIA on a pad?
If it is a personal DIY project, drilling vias on SMD pads may not cause too many problems. The manual soldering process will not cause too much trouble, and components can be easily soldered on SMD pads with vias on. But we suggest making these via SMD pads with the POFV process to avoid problems. Follow the IPC 4761 VII type, all these kinds of vias should be plugged with resin and capped with copper.
The SMT factory suggests to do POFV for the VIA on pads
However, if the SMT patch machine is used in the factory to produce patches, doing so may cause a tombstone phenomenon. Because the surface tension of the solder will pull the components to stand up, causing problems such as cold soldering, desoldering, and poor contact. To prevent this, it is sometimes necessary to open the copper pins. Or does the POFV process for SMD pads with vias on them keep the entire pad flat and convenient for welding?
In addition, if the vias are not plugged well, it may cause tin leakage, further causing the tombstone phenomenon. Therefore, the position of the vias also needs to be considered in terms of process.
Therefore, to ensure the reliability of PCB design and the smooth progress of the process, the vias should not be punched directly on the pads as much as possible. But in the following case, punching the vias on the pads is not a big problem and is OK.
Case 1:If vias are drilled on the back of a large pad
If vias are drilled on the back of a large pad, such as vias on the pad of a MOSFET to improve the heat dissipation of the MOSFET, this is OK. It should be noted that the vias on the large pad need to be evenly distributed to ensure that the pad is evenly heated. But we suggest making these via SMD pads with the POFV process to avoid problems. Follow the IPC 4761 VII type, all these kinds of vias should be plugged with resin and capped with copper.
Case 2:Suppose vias need to be drilled on a thermal pad
Suppose vias need to be drilled on a thermal pad, such as vias for heat dissipation of an IC since there are no pins to be soldered in the middle of the chip body. In that case, there is no need to consider issues such as tin leakage and cold soldering for vias on the IC heat dissipation pad. But we suggest making these via SMD pads with the POFV process to avoid problems. Follow the IPC 4761 VII type, all these kinds of vias should be plugged with resin and capped with copper.
In summary
Whether vias can be drilled on the pad needs to be evaluated and decided based on specific design requirements and process conditions. At the same time, parameters such as the location, size, and number of vias also need to be considered to meet the requirements of circuit performance and reliability. In actual operation, it is recommended to consult a professional PCB design engineer or PCB manufacturer for accurate advice and guidance.
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