Ian,

Using conformal coatings as an under fill is not recommended. The
material is not "designed" for that type of use
(curing/dryng issues due to lack of exposure to the atmosphere plus CTE
issues). Please use materials that are designed for use as an underfill.
This is paticularly true for class 3 products!

David A. Douthit
Manager
LoCan LLC

Fox, Ian wrote:

>Fellow techies, a BGA related question. We're just starting to design BGA's
>into some new designs which are class 3 high rel assemblies and I am asking
>myself questions about the ability to adequately conformally coat under the
>packages. Our standard coating is a solvent based acrylic and we are using a
>456PBGA device and a 429CBGA device, both on 1.27mm pitch, as the maximum
>sizes so far and I'd be interested to hear what other class 3 builders have
>experienced when applying the coating.
>
>Regards
>Ian Fox
>Goodrich ECS
>Birmingham
>UK
>
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