Steve,
Your complaint, if I read it correctly, is a classic one for all of those
people that follow industry and military specifications regarding
reliability, such as MIL-STD-217, and accelerated testing, such as JEDEC.
The reality is that reliability does not work with a one-size-fits-all
approach, but instead is sensitive to materials, geometry, and lifetime
environmental loads.
Many groups take a physics-of-failure approach to reliability, which allow
them to accurately predict time-to-failure using a knowledge of wearout
failure mechanisms, validated failure models, and acceleration factors that
correleate results of accelerated tests to expected field behavior.
Best Regards
Craig
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Steve Joy
Sent: Tuesday, June 05, 2001 12:10 PM
To: [log in to unmask]
Subject: [TN] voids in BGA, but really reliability in general
I am a little confused about BGA voids and reliability.
How many field returns per year do we collectively see? My experience over
the last several years was 0. Don't recall ever seeing one. But we all
build to specs that mathematically predict some defects. So where are they?
So it must meaqn the spec requirements are excessively tight. The
characteristic life curves I developed showed that assemblies are
incredibly robust. Of course, that is using the accepted acceleration
factors.
Which is my point. Why can't we use realistic (or better-experimentally
defined) limits? I have run assemblies beyond 1K cycles (of -45C to 85C)
with 70% voids and seen no failures. I am talking millions of joints in
many package styles.
Is there any industry group looking at this kind of problem?
Steve
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