On 4/7/17 3:45 PM, Charles Steinmetz wrote:
Bob wrote:
The epoxy over wire bond construction approach
is low cost, and not very experimenter friendly.
It is also extremely unreliable, particularly WRT environmental effects
such as temperature changes, humidity, and atmospheric pollutants. In
my view, it is unsuitable for use in anything but dirt cheap, purely
disposable devices like greeting-card audio players and disposable cameras.
Interestingly enough it *is* used in space flight hardware. It is much
less expensive, lighter weight and easier to inspect than thick film
hybrids and similar schemes.
You can can do a pre-cap inspection, then apply the potting material,
and then you could even xray it to see if the bond wires moved or something.
A flipchip with a blob is even better.
It's even reworkable (e.g. you can soften the blob & solder and scrape
the die off and bond a new one down).
I suspect that there is a wide variation in the material you blob on
there and so forth.
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