Wee Mei,

Check on the Tg (Glass Transition Temperature). I believe you have greatly exceeded this
temperature. When this occurs it is not unusal for surface contamination to "sink" through
the coating.

I have often asked the question about those temperature specs. The answers can be quite
interesting but of little use.

 You must use coatings that have a Tg higher then your expected operational/ambient
temperatures.

David A. Douthit
Manager
LoCan LLC

> Some assembled boards were coated with Humiseal 1B31. After the ESS
> tests at 110 degree C, dirts were found on the board and component
> surfaces on both sides. I have checked the data specification on 1B31
> and found that under cured enivronemnt, the coating should withstand -65
> to +125 degree C.
>
> Can someone advice me what could be the cause of this problems?
> Your assistance is greatly appreciated.
>
> Regards - Wee Mei
>
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