I use silicone coatings. We cannot use the tape test, since no 
     adhesive tape that we have found sticks to the silicone. All tape 
     tests failed between the tape and coating.
     
     We have used alternate methods. We used wet 3-1753 (or 1765) as an 
     adhesive between the coating and a substrate used for pull tests. 
     
     In every test, the failure mechanism was cohesive, within the coating. 
     The only problems where adhesive failure occurred was with one vendor 
     who was shipping "dirty" boards.
     
     Aric Parr
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: RE: Conformal Coating Adhesion Testing
Author:  [log in to unmask] at internet
Date:    11/22/96 1:09 AM


 I recommend that you read through ASTM D3359 "Methods for Measuring
Adhesion by Tape Test"  and a recent CRADA report "Evaluation of 
Low-Residue Soldering for Military and Commercial Applications: A Report 
from the Low-Residue Soldering Task Force".
     
The CRADA study included coating adhesion evaluation using ASTM D3359 like 
tape adhesion tests on MIL-I-46058C coupons.  There is a good description 
of the test, the sample conditioning and some of the pitfalls of the test.
     
Experience is needed to get consistent cut and peel-by-tape testing.
 Every cut has to be made with a good sharp blade.  An experienced
operator examines his blade often under magnification and replaces it at 
the first sign of wear.  Also, he/she is able to apply consistent 
pressure on each cut.
     
     
Mary Davis
Sr. Material & Process Engineer
Alliant Techsystems
206-356-3311
[log in to unmask]
 ----------
From:  Yuen, Mike[SMTP:[log in to unmask]] 
Sent:  Thursday, November 21, 1996 7:04 PM
To:  [log in to unmask]
Subject:  ASY: Conformal Coating Adhesion Testing
     
     
     
I need any information of how to test the adhesion of silicone conformal 
coatings.  I have heard about performing tape tests, but I would like 
more
information.  Currently, we are using Dow Corning 1-2577 and 3-1765.  Any
     
help would be appreciated.
     
Heather Benedict
Process Engineer
414-751-5490
     
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