Bob,

For no-flow, or flux-underfill type underfills I had pretty much concluded
that rework after being cured was not practical unless the substrate was
LTCC or alumina, and even then, success is not guaranteed.  Good operator
skills are an asset.

For post-applied capillary style underfills, just make sure you have done
ALL the testing you want to/can do before underfilling the components.

Results may vary.  Subject to the specific underfill utilized...

Steve C

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Wettermann
Sent: Wednesday, June 19, 2013 7:32 AM
To: [log in to unmask]
Subject: [TN] Calling all chemists-the dreaded underfill

Dear TechNetters:

Most of the epoxy underfills on all of our handheld devices are not
practically reworkable, even if you believe the marketing hype on reworkable
underfills. The adhesive force of the underfill either damages the pads upon
device removal, the mask is damaged during the "scrape off"
process. the chemical antidotes sold by the same underfill vendors either
damages nearby parts or is highly caustic to employees.

Has anyone approached this rework challenge differently or could conjure up
a unique way to suggest trying?

Thanks!

Bob W


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