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BGA & Soldermask Issue

Posted: 24 Jan 2022, 14:31
by grog57
Hello,

I recently encountered an issue with the board house regarding the BGA pads and soldermask clearances. The part/package I am using is BGA4N35P2X2_76X76X50N. It was obtained from SnapEDA. Here is what the board house said:

1 - The spacing between highlighted BGA pads only 5.9mil, too close to make soldermask bridge.
Their fix:
A. We will make these BGA pads totally exposed, then no soldermask ink will appear between them.
B. To avoid short circuit during assembly, we will enlarge BGA pad size, make them to be soldermask defined pads and make soldermask bridge between them, then BGA pad size will increased, but exposed BGA pad size for soldering will be 0.2mm, same as designed, and there will be soldermask ink between BGA pads.

I had a bit of trouble understanding what they exactly wanted and how to go about resolving the issue. Its the first time around for me with a BGA package with these small geometries. To avoid future issues what should I have done with the pads and soldermask to fix the issue? For reference I have attached the pattern in "tmp.lib"

Thanks!