Low temperature solder paste (138c)

Chalo said:

Low melting point solders have a couple of limitations for things that take a lot of power. One is that their conductivity isn't always very good, and the other is that they flow at a low temperature and thus can unstick just when things are getting interesting. Because of their electrical resistance, low melting point solder joints potentially could be localized hot spots in an otherwise cool power bus. So your fuse wire might decide to fuse open early.

In the past, I've used pure indium (salvaged from cryo vacuum chamber seals) to do low temp soldering. It's soft, mechanically weak, and expensive, but its electrical and thermal conductivity are even better than the best conventional solders.

Click to expand...

mxlemming said:

I just soldered a battery up using lead solder (I really don't know why this stuff is still sold tbh but it is) and have had very good results. I used 0.25mm copper cut into 7mm wide strips.

The key is to have a really good iron, tin the copper and cell then make the join. All operations can be done with barely 2 seconds of contact and so compared to spot welding where it glows orange, I can't see this being more damaging to the cell.

I also use unleaded solder paste but had trouble making it wet. If you use the ultra low temp stuff you may find this is a problem, depending on whether whatever flux it contains is effective on the nickel cells at such low temp.

Click to expand...