In a message dated 03/21/2000 6:46:27 PM Central Standard Time, Engelmaier
writes:

> Hi Steve,
>  Downhole drilling electronics sees the most severe operational loading of
> any ellectronic assemblies. Design this stuff as robust as possible with
the
> least CTE-mismatch as possible, and be careful with the encapsulant
material
> chosen.
>  Vapor phase soldering is a good idea; but, is there nothing between 253
and
> 215C?
>  Good luck!
>  Werner Engelmaier

Hi Werner!

Yeah, don't have tell me about how harsh an environment these boards will
see, it's easy for anyone to imagine what these boards will go though. They
go into a metal "tool" (about 9 boards per tool) that's about 8"-10" in
diameter and about 10-feet long.

The boards are very thin width-wise (less than 2-inches) and about a foot
long. They are polyimide (I think) PCB's with a lot of copper in them. We
don't control the designs, we're just gonna try and build them.

After going back and looking at the Galden Fluids spec's, they do make a
chemical that has a boiling point of 230 degrees C. I suppose with vapor
phase you don't have to follow the standard guidelines for reflow profiling
of hitting a peak of 20-30 degrees above liquidous of the alloy...that's more
for standard reflow equipment isn't it?

With a chemical like the Galden HT230, I won't have to worry so much that
there will be any temperature lags that one may see with convection or IR
reflow....

I'm still looking for equipment though...

Thanks Werner!

-Steve Gregory-

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