Potting of electrical components in plastic housings 1

[richg1]

Hi,

Can anyone advise on best methods/material to pot electrical components - in particular speaker baskets, mics, switches, battery contacts - in plastic housings?

Cheers,

Rich

 

[itsmoked]

You are heading for frustration, pain, surprise, horror, and prices that would stun a charging moose.

There are a few companies that supply this stuff. Master Bond is an in-your-face company with good documentation and prices that are above and beyond jaw dropping.

You could easily double the price of a product via potting. There are a few other companies, most are very hard to get the attention of. They often don't respond if they don't think you're going to purchase 55Gal/week.

There is one company that makes reasonably priced stuff. I can't remember the name though... Something like CCR or CRC??
One 'C' is short for 'Chemical'. It is a Canadian company. It is a 2 part material that is often sold at hobby electronics shops. White bottles.

There are a lot of compounds that will work for the middle of the road potting applications.

Whatever you choose you have to spend serious effort towards making absolutely sure that the mix (two parts) are thoroughly and correctly mixed. And that you develop a rigid potting schedule(recipe), temperatures, stirring, measuring, and curing that you follow to the letter.

Nothing is worse than shipping something that later separates and bleeds uncured material.

You also have to consider the size of your product since that determines the peak temperature that will occur during cure, an exothermic process.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[sreid]

Take a look at Dolphs. I like the polybutidine; flexible, low water absortion.

http://www.dolphs.com/

 

[richg1]

Thanks...those companies did have some good info and after a bit more reading I understand what's involved a bit better.

Found this article "Resins For Potting
And Encapsulation In Electronics" which someone reading this thread may want to check out for some background info:

http://www.onboard-technology.com/pdf_novembre2006/110609.pdf

***One additional question does anyone know of the impact of potting electronics into plastics with respect to WEEE recycling legislation?

 

[MikeHalloran]

I was just about to point out that potting limits testability, interferes with failure analysis, destroys any salvage value of the assembly, makes simple cut and jump updates impossible, and changes the performance of the stuff inside.

I hadn't even thought about recycling and toxic metal regulations. I guess the guvvamint will have to take your word about what's inside ... like they'll do that.

Is the potting a contractual requirement?



Mike Halloran
Pembroke Pines, FL, USA

 

[TurboXS]

1. You need to ask yourself, why you are potting the parts? Security, safety, environmental?
2. Are the parts designed to be potted? Electro-mechanical parts such as switches and connectors can be a problem.
3. Do you want to hard or soft potting material? (Also see question 1)
4. Do you want to rework or repair the part in the future?

Potting materials range from epoxy resins, polyurethanes, silicone rubbers.

Check out;

Robnor Resins
Electrolube
Dow Corning
GE
Araldite
ACC

Other methods include low pressure plastic injection.

We have used epoxy resins, polyurethanes, silicone rubber, low pressure plastic injection for various products.

 

[richg1]

To explain further:

The reason I am exploring potting electrical components is I am currently reviewing sealing options (IPx7) for a hand held radio device. On reviewing other IPx7 products one method of sealing was potting or gluing (apologies for incorrect terminolgy) around electrical components. This included a speaker basket, volume pot, battery connectors and switches.

However with potting these components (& glue / ultrasonic welding) there will potentially be the rework / repair / recyclability (WEEE, etc) issues.

So I am interested in reviewing this as a potential sealing solution for part of the product but need to explore those above issues further.

Thanks for the advice so far...

 

[sreid]

You should consider a conformal coating such as Humiseal.

http://www.humiseal.com/

 

[itsmoked]

Might I suggest you purchase any one of the 2 dozen submersible VHF handhelds sold in the boating industry. They are surprizingly inexpensive. Buy one. Consider it paid-for-information and dissect it! If I was embarking on your mission I'd definitely do this. You can leap frog a ton of amateur mistakes with a $100.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[itsmoked]

Which is probably less than a quart of potting material these days.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[richg1]

Hi itSmoked,

I had already pulled apart an equivalent product and, whilst having designed sealed mechanical systems previously, I did learn alot. On the product(s) I pulled apart bonding/potting around the electronic components was used on nearly all externally interfacing components.

Not sure if this the right thread but would be happy to expand on my findings from a mechanical sealing perspective...

 

[Higgler]

What about standard 3M caulking?
I'd expect you can't use it for this and someone has a good reason (which I'd like to hear).
It's cheap, works in the bathroom and adhere's to most things? Might be corrosive would be the reason not to use it. I understand that you can buy a non corrosive RTV compound for electrical usage.

kch

 

[itsmoked]

Higgler that's correct regular RTV releases ascetic acid during cure.. that tangy smell which will toast electronics! You can get electrical assembly RTV which uses a different curing process that instead gives off methanol(alcohol) which doesn't hurt boards.

rich1; I don't really follow your last sentence.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[richg1]

Hi itsmoked,

What I was referring to was my current understanding of optimal seal design solutions for plastic parts/assys trying to reach IPx7.

I am also following up on the WEEE implications and will post back when I have a better understanding of WEEE with respect to potting electronics...

 

[itsmoked]

Ohkay!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com