silicone for electronics?

"Silicone" is typically ammonia-curing. So it'll gradually "eat" the connections.

...Jim Thompson

Keywords: "non corrosive RTV". Have a look at 'Tempflex 5145', which is the product I use in the UK for this. Some 'tropical aquarium' sealants have similar properties (they don't like the normal acidic RTV's either!).

Best Wishes

In electronics work, I see both hot-melt glue and epoxy in common use.

A caution: strain relief can be a counterintuitive thing. If you use something rigid like epoxy, all you're doing is making it so that the wires will break at the epoxy instead of at the solder bond; and making it so they'll be impossible to fix when they do break. Solder is a very strong bond (when properly done), so the connections themselves are not what's going to break, even without any strain relief. The switch terminals might break, or the wire might break just ahead of the rigid solder bond. A better approach may be to find some attachment point nearby the switch, and tie the wires to that point. E.g., twist the wires around a bolt somewhere.

Automotive :Sensor Safe" also non acidic. Several types available. Even acidic types probably will do little to contacts since the stuff cures pretty fast. Fumes will go through silicone. I also started to use hot melt glue more, but for a tougher than silicon elastic rubber, I would try polyurathane. Big tubes, The Home Depot. For other things and sticks like mad, Plummers Goop. Plummers Goop is runny, but if you let it dry out a bit, will blob easy. An air gun will hasten a steady non runny state. Its slightly elastic but not much.

greg

That is odd - most of the ones I use around the house stink of acetic acid, which will eat copper (unlike ammonia).

Broad line electronic distributors - such as Farnell - carry a variety of silicone and other potting compounds intended to do the OP's job. Sadly, you have to buy quite a bit, so the lowest possible outlay for one of the Farnell silicones is some $50 for 500 gram of Dow Corning Silastic RTV 9161 silicone rubber plus N9162 catalyst.

You can buy 270 gram of Robnor polyurethane potting compound for about $7.

Like all polyurethanes, you want to make it up in a well-ventilated area.

Use heat-shrink sleeving. This will work better and does not get messy.

ITYM acetic acid. However. Add a dash of your damp alkali of choice to acetoxy cure silicone, and you've got a rapid setting neutral potting compound. Sodium bicarbonate makes it foam a little.

The "silicone" I just used to hang some shower dispensers reeked of ammonia for nearly a day.

...Jim Thompson

But maybe shrink tubing would be more suitable for you.

I read the link. I say its bull. I'm not an expert, just a user. I'll tell another thing. Silicone is micro porous. Supposidly there are different formulations, some say not for use underwater. In my experiance on outdoor automobiles, its use to waterseal screws and stuff is not good. After several years of remaining on steel, I have found the steel rusted, and that because water vapor does go through silicone and causes the rust. Go ahead, and put a dap on some copper and let it there for a day, and another dap for a couple weeks. Remove and check it out. I have not done this test myself. So vapors do escape over a short period. I read a nice article in Nuts and Volts many years ago talking about sealing boating connections. Before using silicone on connections, coat them with enamel first. Lacquer is not a very good sealer either being porous. My front bra on my Datsun just about destroyed my lacquer paint job in a couple hours.Also, if you examine silicone after to exposure to a number of elements, it will discolor as it absorbs that element. Silicon II has different properties and I think its different from the usual electronics grade.Curing time, strength, and stickiness are different from silicone I. You can be sure silicone I is the acedic type. It was always interesting to me, silicone needs moisture to cure.

greg

Which is why most folks use the (more common) vinegar-based stuff. Both stink; pick your poison.

Walter nailed this one: Isolate the motion from the sensitive part. Just use a cable tie that anchors the wire to something rigid.

In Europe it is usually acetic acid curing. Same problem.

"MS polymer" (modified silane - - a different polymer with silane groups only at the ends of the chains) seems to be more suitable and readily available. Generally gives off some butanon-2-oxime when curing. Not nice stuff, but not too much comes out. Alcohol curing silicones also exist, but are rarely seen.

An oxime is C=N-O-H where the C can bind to 2 other things - carbon or hydrogen.

Thomas

Dow Corning has non-corrosive RTV. Expensive stuff compared to hardware store RTV.

Hello Jim,

So you used it again on that corian after you had such a hard time getting the stuff from the old holder off of it?

Regards, Joerg

Actually, ammonia, acetic acid, chloride, and a couple other notable things will eat copper. Reason being, they "complex" the metal atoms and allow it to go into solution very quickly, instead of waiting for it to oxidize, and then eventually dissolving.

Copper won't dissolve very much in 30% sulfuric acid, but muriatic acid can be used for etching circuit boards. Copper soaked in strong ammonia will dissolve, forming a deep blue solution of copper tetraammine hydroxide, which though basic, is soluble because of the ammonia content.

Tim

Yep. The "McKanica" remover worked just fine.

And the old dispensers never came loose in use... just the pumps failed... I guess nearly 12 years is not too shabby ;-)

...Jim Thompson

I should have added, I looked into just replacing the snap-in dispenser pumps.

Do you know what "Life Time Warranty" means... it's the lifetime of the company ;-)

...Jim Thompson

Hello Jim,

These would definitely be unobtanium by now.

In case the company did survive look for that little asterisk and the corresponding foot note: "...except for normal wear and tear" or "...refund or replacement with similar product at the company's discretion".

Also, you were probably supposed to use only 'their' soap in it.

Plastics don't live long anyway. What really shocked me was a pack of mollies. Maybe 15 years old, they all crumpled in my hands. Unpacked the next batch of similar age but different brand, also crumpling. Then I wondered what happened to the mollies that are currently engaged in the job of holding in a screw or something.

Regards, Joerg

For your particular situation you may not need to use a chemical means of anchoring the wires. I find that using a short length of heatshrink tubing which extends over the soldered joint and terminal provides both insulation and stress relief. It is much cheaper than buying a whole tube of silicone rubber or other chemical.