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I work at a place that sells LED strip lights and we don't have an engineering team, so I am hoping that someone can help me figure out what is going on because I've tried everything and I haven't been able to figure out what is happening through experimenting or asking my vendors.

I want to start carrying these IP65 solderless strip light connectors and have tested them with ten different kinds of IP65 silicone sheath LED strips. My initial tests went great and the connectors were able to successfully bite through the silicone and make contact with the solder pads. Everything conducted electricity perfectly fine and after running it through the IP testing it was able to help the strip maintain its IP65 rating. Then a few weeks ago I was testing the connectors with a new strip light from a different company and I saw that all of my solder pads had turned a blackish-green color where they had made contact with the connector:

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The picture above is the back of the strip. The connector has these teeth that are not copper (and I'm not sure what type of metal they are because the vendor is being weird about it) and the teeth sink down through the silicone sheath and into the solder pads:

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I tried running a few experiments and used the same strips that have a different type of silicone sheath and that one doesn't appear to be oxidizing yet (but it's only been a few days) and I've also tried doing some with the original problem silicone sheathed strip with and without silicone sealant. It looks like when I use the silicone sealant in conjunction with the original silicone sheathed strip it starts to oxidize:

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But unfortunately the connectors aren't able to seal properly without the use of a silicone sealant. My early tests with my original ten strips used strips that had an LSE 3M backer applied before they put it into the silicone sheath. As soon as I saw the oxidation on the new strips I went back and cut open some of my original strips with the 3M inside that I had used the same silicone sealant on to see if the oxidation had perhaps just been hidden by the 3M backer, but when I cut a few open, they were completely fine:

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I have asked the strip manufacturer and the connector manufacturer and no one seems to know why this could be happening. I'm basically a pencil pusher who knows just enough about electrical stuff to be dangerous, so I'm not sure if this is a chemical reaction from the silicone sealant mixed with the sheathing on the strip or if the 3M on my first batch of tests somehow helped the strip's solder pads to not make contact with the bottom sheathing or what. Does anyone out there have any ideas as to what could be going on? I super appreciate the assist! Thank you!

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  • \$\begingroup\$ This may be a better question for Chemistry.SE. But in general, as I'm sure you're aware, copper is quite prone to oxidation. Is it feasible for you to tin the pads of your strips with some solder before connecting? I would guess that will likely eliminate this issue. \$\endgroup\$
    – Shamtam
    Feb 3 '21 at 2:11
  • \$\begingroup\$ I think it is unlikely that the silicone is either reacting with the copper or catalyzing the oxidation of the copper. Much more likely is a) moisture, or b) contact with a different metal. \$\endgroup\$ Feb 3 '21 at 2:12
  • \$\begingroup\$ Besides this question should be answer for a chemist, I want to know, what kind of flux are you using to solder those leds? \$\endgroup\$
    – marcosbc
    Feb 3 '21 at 2:26
  • \$\begingroup\$ I suspect that @MathKeepsMeBusy has it right in (b). The prongs are obviously a different metal. You are placing two dissimilar metals in contact with each other. Add to that any condensation and along with the ambient atmosphere (containing who knows what) and other nearby chemicals and you have galvanic corrosion. You've been set up by the manufacturer for failure. \$\endgroup\$
    – jonk
    Feb 3 '21 at 2:32
  • \$\begingroup\$ does the uncured silicone sealant smell like vinegar? \$\endgroup\$
    – jsotola
    Feb 3 '21 at 3:29
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If you are using an acetic acid cured (acetoxy) silicone that would explain the corrosion. It should never be used with electronics.

Only use a non-corrosive type of sealant designed for use with electronics, such as ASI 338. They tend to be a bit more more expensive and slower curing but they won't rot your circuitry and they don't release ionic (conductive) moisture.

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  • \$\begingroup\$ Thank you! I've ordered some of the sealant you recommended and I'm hoping that will solve my issue. :) \$\endgroup\$ Feb 4 '21 at 0:47
  • \$\begingroup\$ @BadAtElectronics Hey, how did it work out? \$\endgroup\$
    – SusanW
    Aug 8 '21 at 21:23
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    \$\begingroup\$ @SusanW The electrical grade sealant got everything taken care of and there has been no more corrosion! In fact we have started selling it to go along with our strips and connectors :) Thanks for asking! \$\endgroup\$ Aug 9 '21 at 22:16
  • \$\begingroup\$ @BadAtElectronics Great news, and really interesting, thanks. I love it when it's a matter of the Right Tool For The Job - nice feeling that there's some crazy chemist out there somewhere who's got your back :-) \$\endgroup\$
    – SusanW
    Aug 10 '21 at 0:05

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