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July 1998

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Subject:
From:
Aric parr <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 27 Jul 1998 07:40:12 EDT
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1) Don't dip it if theres any problem, you get a thicker buildup on one
side relative to the other.
2) Use a soft coating that stretches (some silicones and urethanes are in
the shore A scale) and absorbes almost all of the CTE mismatch.
3) The supplier can provide a recommended reflow and cooling profile. Make
sure you're oven is set within the profile.

ARIC PARR
Sr. Manufacturing Engineer
Eaton Corp
1400 S. Livernois
P. O. Box 5020
Rochester Hills, Mi 48308-5020
[log in to unmask]
248 608 7780
Fax: 248 656 2242
-------------
Original Text
From: C=US/A=INTERNET/DDA=ID/TechNet(a)IPC.ORG, on 7/22/98 11:13 AM:
To: Aric Parr@01635@Lectron_RH,
EatonWHQ@CorpMail@WHQCleveOH[C=US/A=INTERNET/DDA=ID/TechNet(a)IPC.ORG]

  REGARDING           ASSY:Reliability, SMT

With regards to surfmnt glass diodes (melf-type), how does one protect the
body
from conformal coating. In the past, we sleeved the axial body to protect
it from
CTE mismatch. I haven't yet contacted Mfg about the exact P/N of the
conformal
coat material. Is this necessarily the reason for crack initiation? Could
the cause be
the 'cooling' slope during reflow, thereby allowing the coating mismatch to
propogate the cracking?

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