> Carel , If this module is a ceramic substrate or even a soft substarte with
> smll ceramic carriers , on a copper slab or some other sort of slab of
> powdered metal -....
The substrate in these is alumina, so it's important to follow
Hank's comments. Expanding on those, any heatsink you buy will not
be flat enough without machining, ideally with a large diameter
'fly' cutter. You are also looking for a good surface finish with
machining ridges barely detectable with a fingernail. As well as
flat (50um or .001" over the module area) clean is important. No
swarf, grit, hairs or solder splashes under the module.
Skimming the heatsink will also give you a bare metal surface for
good rf contact between the flange and the metalwork. The common
black finish is an insulator.
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