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Date: | Thu, 16 Jul 2020 17:46:32 -0400 |
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Richard,
you got good feedback already. One trick worked in the past is to
put coating mixture in vacuum slightly (you need to keep your eyes on
it and run few experiment). After mixing, the chemical reaction
between the 2 parts will create some bubbles upon curing. if you put
the fresh mixture into vacuum oven (with glass door you can watch
for it), you vacuum until it foams up and immediately release the
pressure (increase to room atm- stop vacuum), the mixture will
settle down with bubble free - if repeat process 2 or 3 times. you
need to use the processed mixture immediately (you lost floor life of
the spray... provide your coating formulation allow sufficient time
for the floor life). caution. if you vacuum too much, you removed
curing agent - small molecule stuff, and the coating will not cure
using normal curing schedule(you need to run DSC to validate it).
jk
On Jul 16, 2020, at 12:56 PM, Stadem, Richard D wrote:
> One of the client companies I work for builds extremely high-
> reliability propulsion control systems. For them, bubbles in the
> coating between fine-pitch ASIC leads are a defect condition. We
> are exploring options for elimination of the bubbles.
> The bubbles are not present in the sprayed on coating, and we have
> tried lightly brushing the leads to further "thin out" the coating
> before the CCAs go into the curing oven. No webbing or bubbles are
> seen at that point but manifest themselves after curing.
> I am not an expert at coating but I do know a bit about it. I was
> wondering just what might be the cause of the bubbles, and how to
> prevent them from happening? Any information is greatly appreciated!
> dean
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