Don't remember who said it first. That BGA guru in NH said it best, what's
his name again and where has he been lately. BGA's ain't no big deal.

Your question is valid and often repeated as are the ton's of answers. I
used to simply reduce the PCB pad size by 20% of the BGA pad size and over
print the PCB pad size by 10% as a function of the stencil design opening,
or was it the other way around. You need to get a focus on the stencils as
well.

Opinion still abounds here - especially when going below, say, .8 mm CSP
types. You'll be there soon enough and still no real problems. Does get
intersting for simple folks like my self when designing, processing, and
reworking (especially reworking) when below .5 mm stuff as uBGA's.

Not really trying to be funny here but some of the basic PCB pad size
formulations kinda revolved around this formulae. Pay for it if you must as
IPC stuff or some other guru's advice. Someone better than me has the
answers as in the IPC archives and throughout industry.

I will say, BGA's in general are the nicest little parts to work with on the
planet. Some exceptions exist but the soldering and solder joint making
processes work very well and placement and self alignment characteristics
are great. And on it goes.

MoonMan

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