Indialloy 1E, from Indium Corporation.
They now say 118C, but the roll I have here says 117, IDK why.
Indium Corporation offers low-temperature alloys, solders, sealing materials, and thermal interface materials to solve the problems in electronics assembly.
I recommend these guys, they're great to work with, professionally.
IIRC, this was $10 a foot for .031" solder, no flux. That was in ~2006, so prices may have changed.
Thermal conductivity IS better than pastes, but; it's hard to use.
At 160C, I'd have never gotten the HS back off.
There are a bunch of alloys; each suited to a particular application.
When you have a board that has to be assembled in a certain order, and has to be reflowed multiple times, you start with 60/40 lead, and work your way down to this.
We used it mostly to solder heat sensitive optical components for testing; that way we didn't damage them, and we could remove them and send them back.
One of the IR sensors we looked at came with a guard.
For some reason, they didn't tell us who the other customer was, lol.
IR was the wrong wavelength for us, but we tested it anyway. We were on the UV end of things.
One of the worst weeks I had was finding out this wonderful magnetic shielding material we were going to use couldn't be exported from the US.
It had applications in classified things, so we had to jump around like crazy and find something else; we ended up using material from Russia, lol.