you wrote:

>People
>
>I am looking for some assistance in justifying the non-use of silicone
>grease, ie Dow Corning 304, near soldered joints.
>
>Could someone please supply me with a route to suitable
>documentation/reports to support this?
>

Past experience with thermal greases in a military manufacturing environment
has demonstrated the following problems:

1. Thermal grease is removed by common solvent or saponifier cleaning systems.
 Depending on the amount of contamination concentrating in the wash tank,
other product cleaned in the same system may have significant amounts of
silicone residues.

2. Thermal greases can easily contaminate fingers, gloves, cots, mats, totes,
bags and the like.  In this case, any surface making contact with the
contaminated part will spread the silicone.

3. Small hand clean pans of solvent used in low volume military applications
increase the cleaning problem noted in #1 above.

The results of these contamination scenarios are:

1.  Conformal coating with Type AR or UR materials will dewet contaminated
areas.  I won't speak for other coating types - no experience.

2.  Wave soldering can be affected because the liquid flux dewets from the
contamination, and the oxides are not removed and the solder has a harder time
wetting.  The same could affect solder paste to some degree by providing a
physical barrier.

Alternatives exist in the form of self-adhesive thermal pads, curing silicone
or other thermal adhesive, that are easier to use\apply and DO NOT WASH AWAY.
Use that as your lever, thermal grease is not guaranteed to be there when you
need it.

Steve Mikell
SCI Systems
Plant 13

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