Hello John,
I recommend you to check your pads size on your PCB, its can be one of the
reasons for ball to package failure.
If you have bigger PCB pads size than the BGA package pads size, you may
have a problem.
Anyway, each BGAs supplier should have its own pull test parameters for the
BGAs balls.
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Best Regards
Reuven ROKAH
John Perry
<[log in to unmask] To: [log in to unmask]
RG> cc:
Sent by: TechNet Subject: [TN] BGA ball-to-package failures
<[log in to unmask]
>
18/10/2004 22:31
Please respond
to TechNet
E-Mail Forum;
Please respond
to John Perry
TechNet Posting on Behalf of Tom Clifford, Lockheed Martin, Sunnyvale
CA:
I'm concerned about incoming BGA ball-to-package integrity. All our
solder-joint-cycle reliability predictions deal with cyclic-fatigue
shear failure thru the solder-joint fillet, top and/or bottom. And,
most t-cycle failures do occur thru the fillet, as anticipated.
However, we have seen, dramatically, that BGA balls can pop right off
the interface at the bottom of the BGA package, in "premature" failure.
Certainly this sort of failure cannot be predicted on fundamental
grounds, or even predicted based on actual test, or compensated for in
our component/PWB selection/design/processing. If the BGA ball is
"weak" at the ball-package interface, all prediction bets are off!!! We
are at the mercy of the supplier and of that particular
part...P/N/...lot...batch. Additionally, the exposure will get worse,
in the hi-rel mil-aero world, as BGA applications increase in number and
consequence, and as supply-chains expand.
I'm thinking the industry (users and supplier/packagers) should do at
least these things:
1)Develop or identify some sort of standard physical test (shear or
tensile) to measure the as-shipped or as-received strength of the
ball-to-package joint, probably room temperature, maybe at an elevated
temperature.
2)Start gathering a data base, linking mean and variability to material
and process.
3)Start relating this relative ball-to-package strength data to maverick
failures at the interface, in t-cycle testing.
4)Depending on results, and if these failures persist in mil/aero
applications, consider adding a suitable qualification and
lot-acceptance test and criteria to incoming BGAs.
Certainly the causes and consequences and fixes will be and probably are
being addressed, but industry recognition of the problem, up-front would
be useful. Perhaps the "problem" has already been solved, but my guess
is that it needs some attention, to help move it way down the list of
reliability concerns.
Comments? Tom Clifford
Mike Green
Production Design Engineering
Dept 7JGS; B157; Col 3D3
Lockheed Martin Space Systems
1111 Lockheed Martin Way
Sunnyvale, CA 94089
office 408-743-1635
Synergy works at LMC. "Show me the data."
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