Re: The ohnosecond

In article <pan.2005.11.08.15.18.27.74501@xxxxxxxxxxx>,
Rich Grise <rich@xxxxxxxxxxx> wrote:
[...]
>> The potting compount attacked the capacitors.
>
>You're using incompatible parts/compound

So I found out. A sealed housing doesn't have this problem.
>
>> The potting compount shrank as it hardened and ripped parts loose.
>
>You didn't allow for shrinkage.

Yes I had but not enough for the batch that got made.

>> The potting compount had holes in it.
>
>You didn't de-air it (i.e., pump it down in a small vacuum chamber)

I sourced the process and yes it was de-aired before use by the people
that did it.

>> The board because noisy after potting.
>
>Incompatible materials, poor layout

Materials again.


>> The board just doesn't work anymore.
>
>Something must have broken - maybe from the shrinkage, so this isn't
>really a different item.

I actually broke it apart to try to find out what happened. There were no
obvious shrinkage effects.

>
>> The potting compound leaked into the connectors
>
>Using incompatible connectors.

Not, the connectors so much as the layout.

>
>But, admittedly, good, resilient potting compound is horrendously
>expensive - maybe you should try just "conformal coating".

No, just put it in a housing and be done with it.

Where I work we still call conformal coating "circuit stop" even though
"circuit coat" isn't sold anymore.

Conformal coating just makes trouble.

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Relevant Pages

  • Re: The ohnosecond
    ... >A sealed housing can get expensive. ... I depends a bit on the layout of the ... The potting compount shrank as it hardened and ripped parts loose. ... The board just doesn't work anymore. ...
    (sci.electronics.design)
  • Re: The ohnosecond
    ... I depends a bit on the layout of the ... > The potting compount shrank as it hardened and ripped parts loose. ... You didn't allow for shrinkage. ... Using incompatible connectors. ...
    (sci.electronics.design)
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