- Peel test with an adhesive tape will most probably not work because normal 
adhesives do not adhere well on silicones.

- A simple and quick, although not too precise method is to cut the coating 
with a sharp knife or blade 7 times in 1 mm distances and another seven 
times in the perpendicular direction, such making 36 1x1 mm2 pieces of cut 
out conformal coating. Be sure to cut hard enough to make the bottom of the 
cut reach the substrate. Then use a brush and wipe several times over these 
pieces. After this you have to grade the result:
1) All 36 pieces are sticking on their substrate, no delaminations, even not 
at their edges: congratulations, you've got the best performance.
2) There are one or more lift offs only at the edges of the pieces.
3) One or more pieces have lifted off (complete or partially).
As said, the method is not too precise, but should allow some reference 
testing in the sense of: yesterday we got a better performance. So its good 
for testing "life" products and doing some control of the manufacturing 
process.

- The better one is to glue two stripes of your substrate together, using 
the conformal coating as the glue. Use stripes which have a surface 
representative to the surface of your actual product. You have to control 
the area and the thickness of the "glue". As an idea, 5 x 5 mm2 and 0.1 mm 
thickness in general should be ok. Curing of the coating is critical in the 
case of DC 1-2577. Since this type of coating needs moisture for curing, be 
sure to wait long enough and dont use to thick and to wide glue lines. Also 
solvent has to be removed. So a thin, long glue line should be better in 
this case. Then do pull testing of the stripes. The force you need to 
separate the stripes and the location of the failure (in the glue, at the 
interface to the stripe or a mix of these two cases) will give you a measure 
for the performance of your conformal coating. This type of testing is good 
for selecting suitable conformal coatings or surfaces. It is also good for 
testing degradations in the adhesion of the conformal coatings after stress 
(like tempering at elevated temperatures, temperature cycling etc.).

Hopefully this will help a little.

Ulrich Korndörfer

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************