Graham,

Back in the day, we would have approached as much as we could with hybrid
technology.  

Eutectic die attach on ceramic [High temp co-fired ceramic, alumina
substrate within metal package, or Low Temp Co-fired ceramic], etc.  Way
back, there was even eutectic attach for passives - if properly
metallized...

Being in a hermetic package, no conformal coatings...

Being a potentially highly corrosive environment the package is truly put to
the test.  Drawing upon implantable medical technologies [also a corrosive
environment, believe it or not], there are multiple packaging options
available including stainless & titanium.

Just a different persective...

Steve Creswick
Sr Associate - Balanced Enterprise Solutions
http://www.linkedin.com/in/stevencreswick
                         616 834 1883






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