Tan,

I would recommend splitting the sample group into two sets and to perform 
adhesion testing before and after thermal shock. 
Or, you could just perform adhesion testing after thermal cycling and if 
adhesion is acceptable then there is no reason to do adhesion testing 
prior to cycling.  But, if adhesion is not acceptable, then you'll have to 
work backwards to identify if the adhesion was acceptable prior to cycling 
after coating.

A point to consider though is if there is a change after thermal cycling, 
such as the adhesion decreases, to not to jump to a conclusion that 
something bad is happening to the Parylene.  It may be possible that other 
factors could contribute to a loss of adhesion, such as processing 
residues being baked out from the substrate during the cycling and forcing 
a loss in the coating adhesion.  Ideally, the pre-coating processing would 
remove such residues prior to coating, but I am not aware of the exact 
details of your process/application. 

A couple words regarding the test methods.  The ASTM is more widely used. 
I've not heard a good explanation for the 3 hour immersion in boiling 
water.  To my knowledge, I don't think ASTM has solved the issue regarding 
specifying a replacement tape for the Permacel which is no longer 
available.  The issue with the TM-650 is that 3M makes two different 600's 
with different adhesive levels and the method does not specify which 600 
to use.

Lamar Young
Specialty Coating Systems, Inc.
7645 Woodland Dr.
Indianapolis, IN 46278
(317) 244-1200 Ext. 276
www.scscoatings.com



From:   Tan Geok Ang <[log in to unmask]>
To:     <[log in to unmask]>, 
Date:   02/13/2015 10:10 AM
Subject:        Re: [TN] Adhesion, Polymer Coating ( IPC-TM-650 2.4.16 )
Sent by:        TechNet <[log in to unmask]>



Any comment or advice?

________________________________________
From: TechNet [[log in to unmask]] on behalf of Tan Geok Ang 
[[log in to unmask]]
Sent: Thursday, 12 February, 2015 5:42:25 PM
To: [log in to unmask]
Subject: [TN] Adhesion, Polymer Coating ( IPC-TM-650 2.4.16 )

Will like to check whether it is a common practice  to subject parylene 
coated boards to thermal shock cycles before performing adhesion test 
method in accordance to IPC-TM-650 2.4.16 (similar to ASTM 3955)?

At the same time, Section 4.0 (Apparatus or Material) of IPC-TM-650 
2.4.16, does not indicated what tool is used to create the pattern under 
section 5.2 (though it refer to IPC-DD-135 which is an obsoleted standard) 
as the line width of the pattern is 0.1mm. Razor blade thickness is about 
0.2mm.

Hope to get advice you all.



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