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Reply To: | TechNet E-Mail Forum. |
Date: | Fri, 18 Dec 1998 11:33:48 -0600 |
Content-Type: | text/plain |
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Address,
I have a 12 layer, 9 x 9, .062 PCA with 4 50mil pitch BGAs. Two (2)
of the BGAs are normal 300+ IO perimeter and full array OMPACs. The
other two are 500+ IO Perimeter BGAs with aluminum bodies.
We suspected shorts on both packages and on several PCAs. An outside
lab provided us some excellent and I mean excellent Radio Graph photos
@ 80KV.
We found the suspected shorts as well as solder ball voids,
everywhere. The BGA pads are .025", again on .050" centers. I
estimate some solder voids (air pockets) to be as great as .054"
As a note, our design does have vias in the BGA pads, however, we have
soldermasked the solder side for obvious reasons. Worst case voids do
have vias in them. Voids are apparent all over. The same condition
was not witnessed on the OMPACs. This condition is only witnessed on
the Aluminum Package BGAs.
I'm going to run some more thermal profiling on these BGAs only, but
request the following from the group.
1. What advice can anyone provide on this problem. Any other angles
are appreciated.
2. Are there any thermal profile considerations on these BGAs and what
changes can be made without influencing changes to the OMPACs.
3. I'm using Convection Reflow.
4. Could the solder balls on the package be defective? I don't see
this as being a problem.
5. I know the solder balls are not hygroscopic, so can moisture be
creating these ball voids?
Again, any input is appreciated.
Thanks,
John Gulley
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