Are you SURE it needs to be potted?

The main problems with potting are:

1. Inhibits cooling, especially if the cube is thick.

2. When the parts temp cycle, the parts rip off the PCB.

On several occasions when I was forced to protect boards from
moisture, I simply DIP-COATED the boards. For that, I used a compound
normally used to insulate pliers,
which comes in a spray OR a dip, named "Plasti-Dip". It is available
in clear, red, black, blue, and yellow (maybe more) colors.

This coating is being used commercially by my client to protect a tiny
safety device from
moisture and petroleum lubricants. I have never seen the coating fail
for any reason.

The advantage of this method over potting is that while the coating is
strong, it is also flexible. It also passes heat well (especially the
blue and black versions).







On 7/1/09, Jesse Lackey <jsl-ml@celestialaudio.com> wrote:
> Hello all, I have a client who wants to pot the board I'm making to make
> it as indestructible as possible.
>
> I haven't done this before, and wonder a few things.
> Maybe someone would like to offer advice?
>
> Heat.  The components being potted generate some heat, not a lot, and
> there will be a heatsink of some sort on the underside of the board.
> (only the top is being potted).  So I'm not too worried about this.
>
> My main concern is what being potted may do the following component types:
>
> Electrolytic caps: they have some sort of safety vent, right?  If
> sealed, and should disaster occur somehow, I figure failing in potting
> couldn't be any worse than failing in open air?
>
> Inductors: I'm using 5 for dc/dcs, 4 of which handle significant current
> (2amps) in pulses.  They get pretty warm.  I just wonder if the potting
> compound could cause them to change behavior (inductance value, current
> capacity) in a significant way, by possibly squeezing them a little when
> it cures?  Seems unlikely, thought I'd ponder.
>
> Crystal: there is a 10mhz xtal that needs to be reasonably accurate
> (250K baud serial coming in), and I remember somebody here saying once
> how potting a board made their xtal drift.  How problematic might this be?
>
> Any advice appreciated.
>
> Thanks all-
> J
>
>
>
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