Hi, Matt,
The commonly used coatings are either Acrylics, like Humiseal 1B31 which we
use, Urethanes or Epoxies. All three have the same good resistance to
moisture and salt fog, but the difference between them is that Acrylics are
not very chemical resistant (which makes them great for rework), Urethanes
are more difficult to rework and need much more sggressive stripping agents
to remove them, and Epoxies are darned near impossible to shift. I remember
the days of PC54, which was the common coating for military PCBA's up til
the early 80's, and repairing boards nicely was a major pain.
If it's purely Humidity and Salt Fog you're up against, use an acrylic
conformal coating. It's easily applied by brushing, dipping or spraying.
Peter
"Gray, Matthew D HS-SNS" <[log in to unmask]> 22/05/2003 09:54 PM
Sent by: TechNet <[log in to unmask]>
Please respond to "TechNet E-Mail Forum."; Please respond to "Gray, Matthew
D HS-SNS"
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cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Subject: [TN] Conformal Coating Application Method for BGA
Hello -
I am requesting feedback to material and processes that have provided
environmental performance protection for BGAs and other large array
packages. The performance environment of consideration is corrosion and
humidity.
Can users provide particular details regarding application process spray
(inclusion of steps used for flood/fill/etc), dip, other, and material that
has provided a high amount of coverage and ability to protect electrical
connections and components in humidity and salt fog environments. Ideally,
these materials are below the parylene step. All feedback is appreciated.
Regards - Matt
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