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March 2002

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Subject:
From:
Dave Hillman <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 20 Mar 2002 08:15:14 -0600
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Hi Bruce! We are routinely putting acrylic conformal coating over plastic
BGA components without using underfill for avionics use environments. We
did a fair amount of testing looking both at paraylene and acrylic prior
implementation. This work was published at the IPC APEX 2000 Conference in
Long Beach (the paper title was "An Investigation of the Effects of Printed
Wiring Board Surface Finish and Conformal Coating for Ball Grid Array
Assembly"). Can you expand on your concern of "entrapped air"? We have not
seen any issues for that topic after 2 years of production experience.

Dave Hillman
Rockwell Collins
[log in to unmask]




"Misner, Bruce" <[log in to unmask]>@ipc.org> on 03/19/2002 01:48:38 PM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
       to "Misner, Bruce" <[log in to unmask]>

Sent by:    TechNet <[log in to unmask]>


To:    [log in to unmask]
cc:

Subject:    [TN] Conformal Coating BGA's


My question of the day: Is anyone conformal coating (not parylene) plastic
BGA's on FR-4 in Hi-Rel applications (aircraft; -20 to +71C ambient
operating temperature requirement) without benefit of an underfil?  If yes,
has entrapped air been a major issue?  Anyone care to comment on this
approach?

Regards,
Bruce Misner

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