Hi Technet! A number of folks have asked which underfill materials we have
been using but I haven't sent out a response. We would like to get the DOE
investigation results statistically crunched first before we let folks know
what materials we have been using. I promise to send out a response to the
TechNet community once we can review our data first. Thanks for being
patient. There are both reworkable and nonreworkable underfills in the
study.

Dave



                      "Macko, Joe @
                      IEC" <Joe.Macko          To:       "'TechNet E-Mail Forum.'" <[log in to unmask]>, "[log in to unmask]"
                                                <[log in to unmask]>
                      02/06/2003 09:43         cc:
                      AM                       Subject:  RE: [TN] Speaking of Underfilling...






Dave,

We are considering the use of a post reflow underfill for BGAs.  What
underfill material are you successfully using?  Is it reworkable?


joe
-----Original Message-----
From: Dave Hillman [mailto:[log in to unmask]]
Sent: Thursday, February 06, 2003 5:35 AM
To: [log in to unmask]
Subject: Re: [TN] Speaking of Underfilling...


Hi Steve! We have been using underfill materials for about 2 years very
successfully on some of our designs. Our underfill procedures/guidelines
mimic the underfill material supplier application recommendations - we
didn't need to create any new or special procedures. We utilize underfill
on both BGA and CSP depending on the use environment the assembly has to
live in, although the thermal cycle reliability is more of a driver than
vibrational reliability for many of our assemblies. We just finished up a
very large DOE investigation which compared the thermal cycle life of
ceramic and plastic BGAs in the underfilled and non-underfilled
configuration. The thermal cycle recipe was -55 to +125C on a roughly one
hour total cycle (we were following IPC-9701). The failure analysis is
underway and I promised Peter/Technet I would pass on the results once we
had the statistical analysis complete. It will be several weeks yet but
when we finish up the microsections I'll pass on some of the findings.

Dave Hillman
Rockwell Collins
[log in to unmask]



                      Steve Gregory
                      <[log in to unmask]        To:       [log in to unmask]
                      m>                       cc:
                      Sent by: TechNet         Subject:  [TN] Speaking of
Underfilling...
                      <[log in to unmask]>


                      02/05/2003 08:01
                      PM
                      Please respond to
                      "TechNet E-Mail
                      Forum."; Please
                      respond to
                      SteveZeva






Hi All!

Peters thread about reworking a single ball on a BGA with underfill,
brings-up a question.

Are there any guidelines, or anything that someone would like to share,
when to use an underfill? Is it something that is determined after ESS or
HAST, and upon seeing failures then, which requires it? Or is there some
sort of established guidelines that one can reference that say; "If you
have BGA's on a assembly that will see "X" loads, then underfilling is
necessary..."

Question to the point; BGA's and Micro-BGA's on a missile...underfill these
guys?

-Steve Gregory-

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