It is vital for R&D and rework. Most all the BGA R&D work on the planet has been done or done near
to death. Therefore, you may feel very comfortable using industry solder paste, profile, acceptance
criteria, and all the rest for most BGA designs and product.

When reworking BGA type devices (who would ever need to do that?), it is essential to use some type
X-Ray to confirm the shortcomings found in most rework processes/equipment. Again, however, when the
designs are right as no traces to close to BGA surface pads, there is little need for X-Ray.

Our company uses a very expensive, very heavy (8000 pounds) machine. It provides what is known as
laminography. We can slice through solder joint layers and use programmed in design/acceptance rules
to attempt accept/reject decisions. Again/again, we use the process for rework once our production
cycle is dialed in with the only reason for rework being part removal when shorts are encountered.

An expensive machine is very neat. It clearly shows solder joint voiding even though industry is
still out on how many, how large, in what location voids are acceptable.

If your dial in your paste prints and reflow profiles, you'll have little trouble - except for
design rule violations. In this regard, we have only two profiles for 800 part numbers with up to 9
different assembly classifications from single sided to multiple sided, flip flip flop, and through
hole stuff. Of course, we had the luxury of having a bunch of Phd's heading up the research years
ago.

None of this probably did you any good, but best wishes anyway,

Earl Moon

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