Ken-

I'm not sure it's the vibration as much as a slight flex induced during the
operation.  Flexing the assembly can cause all kinds of problems, anyone
who's dealt with fractured caps due to proximity to a v-score can attest to
that!  There may be some flex without even realizing it, perhaps one tooling
pin higher than another, a part slightly off center causing a slight bow
against a fixture wall, etc.  I think about designing a new way of
depaneling assys all the time to help reduce these kinds of problems, but
need to learn more about the fab and lamination process.

Good luck!

Bill C



-----Original Message-----
From: Ken Patel [mailto:[log in to unmask]]
Sent: Friday, January 26, 2001 2:06 PM
To: [log in to unmask]
Subject: [TN] Spread the knowledge...let's share...reason for BGA crack


Nothing wrong in sharing a good info to Technet.

I have asked about the possible reason for open solder/crack at BGA to
TechNet few days ago. What we found out that the solder cracks are due to
dremer tool (?) used to remove the break away tabs. So watch out! Our mouse
bite with three hole with solid connection - no good design as it requires
lot of effort to remove break away tab. Hence our assembly house folks used
the dremer tool to remove break away tabs. Vibration of that tool generated
crack at the interface between board and the ball along the entire row
facing the break away tab.

Bottom line, do not use dremer tool and incorporate better mouse-bite design
with 4 or 5 holes with two corner holes half in the FR4 material so that
operator can initiate tab separation easily.

re,
ken patel

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