"Campbell, William (wcampbel)" wrote:

> 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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Can we replace this mouse-bite design with several slots of dimension 0.5" in length and
0.03" in width. Each slot seperated by a tab of 0.03". With slot, you need not apply much
effort to break the tab off. This will not cause flex to the assembled board and BGA balls.
My only concern is whether slot of such dimension is sufficient to withstand the assembly
force without giving way.

I am not a process gal, just want to share some crazy idea of mine. Correct me if I am wrong.

Regards - Wee Mei

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