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I'm contemplating which lead free paste to use for production. It'll be with stencils and a (very) basic oven. Low volume (100s not 10000) of units, some QFN no BGA, 0402 smallest parts. I'm using 100C for hand soldering which is great, but contemplating the SN42/BI57/AG for pastes. Boards are ENIG if it matters.
Should I got 100C, SAC305 or the Bi stuff?
- Comments(1)
A****min
Sep 21.2019, 10:57:06
If you do BGA, stay away from SnBiAg. You are creating a new alloy that has not been verified yet.
One thing with soldering is that always use known, verified solder alloy.
With SnBiAg paste and Sn or SAC305 balls, you get mixed solder with undetermined characteristics.
Sn99, Sn100e and SAC305 are somehow compatible. You don't get the perfect joint when mixing them, but for most of the time, that's not a big deal.
Even that, I don't touch them normally. I stick with SAC305 for low power stuff and 63/37 for heavy stuff.
I really can't say this for mixing high Sn solder with bismuth solder.
Also, one word of notice: SnBi is extremely sensitive to Pb content. Even with Ag added, it's still fairly sensitive to Pb.
If you don't have a 100% Pb-free setup, don't touch bismuth. A little bit of Pb can drastically reduce MP to even below 100C.
