RE>ASSY: Rework of PBGA package 7/11/96
We've been dealing mainly with CBGAs but have become involved with PBGAs during the past year. From our experience, the PBGA becomes unusable following rework. You might be able to save it by redressing the bottom of the device where the balls used to be (they aren't really balls at this stage of the game!), reballing, cleaning, and retesting. For us, it isn't worth it to do this, given the cost of a new package. (FYI, we do this with CBGAs, however.)
We tend to get 15-24 mil standoffs with the PBGAs, but this isn't something that we actively "maintain". It's dependent upon solder paste volume, pad size, any bowing of the BT (and there usually is a little at the corners), etc.
I don't think that pure transmission x-ray is capable of finding solder defects, but we really haven't really used much x-ray with BGA technology after initial process development.
Hope this helps!
Greg Bartlett
Mercury Computer Systems
Chelmsford, MA
[log in to unmask]
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We have the following querries regarding the rework of BGA:
1. During removal of PBGA package having euctetic solder balls (dia
0.6 to 0.9mm) with 63/37 composition, what happens to the shape and
size of the solder ball.
2. Can the removed pbga be again soldered on the PCB.
If yes, suggest the rework steps.
3. what standof has to be maintained for assembled PBGA package?
4. Also guide us to which inspection criteria/ standard is to be
folloewed.
5. In case of X-ray inspection, is transmission X-ray capable of
deflecting the solder defects (specially voids, and insufficient
solder)?
If yes, what range of X-ray voltages to be applied for multilayer
PBGAs. what specification is to be followed?
Thanks in advance
Regards,
S V C patro
Altos India ltd
Gurgaon,
India
India
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Subject: ASSY: Rework of PBGA package
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