Solder

Luke says:

May 30, 2019 at 10:16 am

The bismuth based solders would be nice, but they tend to be rare as hens’ teeth and expensive when you do find them from a local supplier. Also, the low melting point of 139 C is a little bit too close for comfort for some components like high power high temperature FETs that may run up to 150-200 C.

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Luke says:

May 30, 2019 at 10:24 am

Apparently, if there’s any lead involved, such as with pre-tinned wires or leads, the combination of Bi58Sn42 and the lead can lower the melting point to 95 C and create very weak and brittle joints that can be pried apart with a toothpick.

And in general bismuth solders have inferior mechanical properties, being somewhat brittle and stiff even when there’s no lead involved.

AMS says:
May 30, 2019 at 8:10 pm

Having tried quite a few, SN100C (It’s .7%cu, .05%Ni, .009%Ge Balance Sn) is about the best you’ll get other than 37/63 SnPb stuff. Yeah it’s higher temp but it wets well, is eutectic, and shiny, and doesn’t get all dross filled when soldering big stuff like 97/3 SnCu or SAC305.

All from

https://hackaday.com/2019/05/30/the-fascinating-world-of-solder-alloys-and-metallurgy/#comments

-- 

Seeed PCB arrived!

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Also the silkscreen resolution really good, virtually no steps are visible on angled or curved lines, which makes it very usable for advanced graphics.

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Reads

https://hackaday.io/event/19417-kicad-hackchat/log/52201-edited-transcript-of-the-kicad-chat

http://hackaday.com/2017/01/24/slow-motion-frame-will-be-the-new-magic-mirror/