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I am designing a PCB for a BGA footprint image sensor. Due to size constraints, I had to put multiple vias in BGA pads to reach other layers. Via size is .45mm with .35mm drill. Pad diameter is .45mm. Would this create any issues during soldering? I am planning to solder this at home using a home-built reflow oven.

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If you put standard vias in BGA pads, you will definitively have soldering issues. The via will suck away a lot of the solder due to capillary force.

Although, there are methods to mitigate this issue, such as via plugging and "via in pad" which is basically a more advanced way of filling the vias where the via is also plated on the surface, so there is no void at all in the pad. Adds some additional manufacturing cost though.

Also, I'd recommend using a smaller drill size. .45mm via with .35mm drill is only .05mm annular ring, many manufacturers can't even handle this. But most manufacturers can handle down to 0.2mm drill size which would make for a decent size annular ring.

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    \$\begingroup\$ +1 decrease drill size will solve many issues. \$\endgroup\$
    – tobalt
    Mar 23, 2022 at 18:16

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