potting compounds

[Jewraffe]

I am relativly new to the electronics game and seem to have run across a very knowledgeable bunch here. I have cases and cases of failed electronic ignition modules form boat motors that I would like to attempt to repair. However they are all potted. Is there a way to remove the potting material without destroying the electronics or the shell. All the potting is somewhat soft which makes me think it is not epoxy, so I suspect urathane or silicon. Is there a way to positivly identify the potting material. Thanks.

 

[Nigel Goodwin]

If it's soft it's probably silicon rubber?.

 

[stevez]

Just a few thoughts:

A. Call the mfr, they might tell you. If not you've only wasted a little time. Potting is done for a number of reasons - not just secrecy.

B. Others will likely comment on common potting materials (as Nigel did). Assume for each suggestion that they are correct and find out what it might take to remove the material - a solvent, heating, etc. You might waste a few modules but still it's a way.

C. Try some things yourself. Try immersing in hot water of various temperatures - increasing the temp until you succeed, or you ruin the part or the water boils. I suppose you could go beyond 100 deg C if you switched to oil or some other fluid. You could also try some common solvents - alcohol, mineral spirits, etc. Again, the risk is ruining some things but that's part of the cost of finding out.

D. As for/pay for the services of an industrial lab. Someone will be able to tell you what it is - the cost might be a bit steep.

Many potting materials are likely to have taken their final form after undergoing some chemical reaction that isn't easily reversed. Potting materials selected for use in a motor would probably be quite resistant to heat, gasoline, oils and similar materials encountered in that kind of environment. With those things in mind I'd say you are going to have a tough time finding a way to remove the material without damaging the electronics. Only you can decide how much all that effort is worth.

 

[zevon8]

If it is a urethane potting compound, paint remover can soften it or make it " crumbly." It can be a fairly slow process, and of course will damage the paint on resistors, some plastic potting boxes, and is generally a messy job. Many paint removers are formulated to disolve urethanes, most once contained methylene chloride, a nasty chemical that is often regulated in many places, but is the main solvent for urethanes.