[SI-LIST] Re: Potting/encapsulation/conformal coating and SI
- From: "George Tang" <gtang@xxxxxxxx>
- To: "Ray Anderson" <reanderson@xxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 4 Oct 2004 14:33:54 -0700
Yes, you are right. Potting provides better mechanical support for the
components. However, during shake-&-bake tests, we had discovered that some
components pop-off the board in an area where the conformal coating was not
applied. After properly applying the coating, the parts did not come loose
in the additional shake-bake tests. For most commercial applications,
conformal coating may be enough mechanical support for PCBs. In most cases,
it is also not practical to pot a large area on a PCB, and it also comes
with the large weight penalty.
Regards,
George
George Tang
LSI LOGIC CORP.
gtang@xxxxxxxx
-----Original Message-----
From: Ray Anderson [mailto:reanderson@xxxxxxxxxxxxx]
Sent: Monday, October 04, 2004 2:14 PM
To: gtang@xxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: Potting/encapsulation/conformal coating and
SI
George Tang wrote:
>In military electronics application, this PCB sealing process is called
>conformal coating. I did a quick search on the web, and here is one of the
>companies I found which provides this service.
>
>Regards,
>
>George
>
>
Potting and conformal coating are two different things.
Conformal coating is a thin layer of material applied to the PCB that
"conforms" to the boards contour and whos prime use is to seal out moisture.
Potting usually involve encasing a circuit in a "block" of material and
ususally in used to provide either mechanical protection or to inhibit
reverse engineering. Long ago at Calif. Microwave we had a small module
encased in x-ray proof epoxy to inhibit others from seeing what was inside.
Removal of the hard potting material usually results in destruction of
the encased circuitry. One application that I'm aware of actually used a
soft potting material (the consistancy of cured RTV rubber). This was in
a military avionics radar beacon (APM-154). The modules were actually
repairable. One had to pick out the potting cmpound with a dental pick,
troubleshoot and repair the circuit and repot the circuit using the
special molds the vendor provided. This particular application of
potting was mostly for the mechancial protection afforded in hi-G
environments.
-Ray Anderson
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