I don't like either of the ASTM tape tests, either the checkerboard or the
X test. Too much dependence on who does the test or how they do the test
for passing. Also, I don't know about anyone else's products, but we don't
have small elves in the avionics bays scribing our coatings with razor
blades. When I want to know if coating will adhere, I pop the coated unit
into one of Hillman's thermal cycle chambers which are constantly running
IPC-9701 (I think), which is -55 to +125C, 8-10C/min, 15 min dwells at
either extreme. In my experience, if the coating adheres through 50 cycles
of that with no adhesion loss, it will last the life of the product in
service. That thermal cycling is much more representative of what our
products see than the tape pull tests.
*Douglas Pauls *| Principal Materials and Process Engr | Advanced
Operations Engineering
*COLLINS AEROSPACE*
400 Collins Road NE, MS 108-101, Cedar Rapids, IA 52498 USA
*Tel:* +1 319 295 2109 | *Mobile: *+1 319 431 3773
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On Fri, Jun 26, 2020 at 3:00 PM Richard Kraszewski <
[log in to unmask]> wrote:
> We have customers that require this test to be performed on the
> coatings that we apply to their assemblies .
> Internally we require all coatings materials we use to be tested to the
> IPC test method prior to use on any product.
> As a result, we roll that requirement down to the coating manufacturers
> through our distributors. They only ship us lots that pass our requirement.
>
> The test itself is not perfect and can be somewhat subjective.
> I consider it be more "qualitative" in nature, rather than quantitative.
> Able to identify and prevent "really bad" coating batches from being
> accepted and used.
> Therefore we keep the acceptance level on the low side
>
>
> Rich Kraszewski
> Plexus
> Senior Staff Process Engineer
>
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> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of GRIVON Arnaud
> Sent: Friday, June 26, 2020 7:29 AM
> To: [log in to unmask]
> Subject: [TN] [COM] Conformal Coating Adhesion Test Protocol Details |
> Acrylics & Silicone Coatings
>
> [EXTERNAL] This email was sent from outside of Plexus. Use caution when
> opening attachments or links from unknown senders.
> .
> Hi TechNet,
>
> I know that, contrarily to PCB solder mask adhesion tests, adhesion tests
> for conformal coatings are not standardized or covered by shared/uniform
> practices.
>
> Without willing to open a new can of worms, I would be interested by the
> detailed adhesion test protocol/methodologies from those who are
> successfully performing this kind of test in qualification and/or
> production.
> For both acrylics and silicone conformal coatings, say 1B73 for acrylics
> and 1-2577 or RTV-3140 for silicones if coating references can help driving
> responses.
>
> Questions in particular :
>
> - What reference standards are used for the adhesion test
> methodology (e.g. IPC-TM-650 - method 2.4.28 for the tape test) ?
>
> - What types and references of tapes ? This may differ between
> the two considered kinds of coatings.
>
> - For adhesion tests with cross-hatching : tools and blade
> spacings (1mm vs. 2mm) specified
>
> - Acceptance criteria with the related reference standard (e.g. :
> grade xx as per EN ISO 2409 or ASTM D3359)
>
> Thanks in advance for your inputs.
>
> Have a nice week-end.
>
> Arnaud Grivon
>
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