Seymour Snerd
Lifetime Supporter

I found out about these from Terminal Town Terminal Town's Electrical Connector Home Page which is where I buy all my crimp terminals for wiring. I finally used some today and they are fantastic. The splice is made of heath-shrink tubing but the trick is the ring of solder in the center. To splice two wires you simply strip about 3/16" from the end of each one, insert them into the splice from oppositw ends with the bare copper overlapping or "merged" within the solder ring, and heat with a heat gun. First the heat shrink shrinks, then after a little bit the solder melts and solders the two wires together. You know you're done when the solder ring collapses entirely and turns shiny.
Tips:
- It's important not to disturb, and to continue to support, both ends of the splice until the heatshrink has cooled enough to harden. Otherwise the joint can either bend and cause the copper to poke through the soft heatshrink, or perhaps in an extreme case separate entirely.
- Having a reflector on your heat gun helps a lot both here and with any other heatshrink operation. I got my reflector as part of 9 Piece Heat Gun Accessory Kit. at Harbor Freight for $7.50. The reflector is the one with the slanted flat piece, which I bent into a nearly closed cylinder using a pair of needle-nose pliers.
- The shrunk heatshrink looks thin and the whole thing's a little bumpy so depending on the wire's mechanical environment you might want to cover it with another plain heatshrink segment.
I've been using them in particular where I need to "tap into" an existing wire. Cut the wire, strip both ends, then pair up your third tap wire with either end of the cut wire. Splice. Done.
BTW Terminal Town is highly recommended. He now has some crimp terminals who's sleeves are heatshrink and contain glue so after you crimp you hit it with the heat gun and it seals around the wire's insulation. I haven't tried these yet (probably later today), but they sound wonderful:
Terminal Town's Electrical Connector Crimp and Seal/Crimp and Seal