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silicone for electronics?

Discussion in 'Electronic Design' started by [email protected], Apr 11, 2006.

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  1. Guest

    is there a silicone or similar product which works best for
    electronics? I made a toggle switch that has 3 wires soldered on to it,
    and want to protect the connections so they don't come loose or
    bend/crack. I need some sort of silicone that will harden when dry. Any
    suggestions? thanks.
  2. Jim Thompson

    Jim Thompson Guest

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

    ...Jim Thompson
  3. 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
  4. 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.
  5. GregS

    GregS Guest

    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.

  6. Guest

    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

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

    Nico Coesel Guest

    Use heat-shrink sleeving. This will work better and does not get
  8. Ian Stirling

    Ian Stirling Guest

    ITYM acetic acid.
    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.
  9. Jim Thompson

    Jim Thompson Guest

    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.
  11. GregS

    GregS Guest

    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.

  12. JeffM

    JeffM Guest

    ITYM acetic acid.
    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.
  13. Zak

    Zak Guest

    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

  14. qrk

    qrk Guest

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

    Joerg Guest

    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?

    < shaking head >

    Regards, Joerg
  16. Tim Williams

    Tim Williams Guest

    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.

  17. Jim Thompson

    Jim Thompson Guest

    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
  18. Jim Thompson

    Jim Thompson Guest

    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
  19. Joerg

    Joerg Guest

    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
  20. Ross Herbert

    Ross Herbert Guest

    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.
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