[volt-nuts] PCBs with ceramic substrates

David davidwhess at gmail.com
Sun Apr 16 22:30:15 EDT 2017

Conformal coating might help with sensitivity to humidity but I would
not count on it.

Hook corrupts the AC response and settling time in high impedance
circuits.  I did not know it at the time, but I suspect I have seen it
manifest as mysterious linearity errors in integrating converters.

The way to prevent hook is to use a substrate which does not suffer
from it.  For FR4, this could include testing to qualify suppliers.
Early on when Tektronix ran across this, they used other substrate
materials like polysulfone, an amber colored high temperature plastic,
and later a white material which I have not identified.

On Mon, 17 Apr 2017 01:54:15 +0000, you wrote:

>Are conformal coatings the right way to handle this?
>I understand there are kinds of FR4 and G10 that don't have hook. What does
>one do about hook - how are those substrates improved? How does hook
>manifest in circuits?
>On Mon, 17 Apr 2017 03:48 David, <davidwhess at gmail.com> wrote:
>> FR4 has problems with consistency.  Samples can have problems with
>> hook, dielectric absorption, leakage, and sensitivity to humidity.

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