Is it possible to solder Nichrome wire (30AWG) to stainless steel and then the steel to a PCB?
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\$\begingroup\$ If you solder nichrome, won't it melt when it heats up? \$\endgroup\$– pjc50Commented Jul 21, 2016 at 13:04
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1\$\begingroup\$ Such connections are usually crimped or welded, not soldered. \$\endgroup\$– Dave TweedCommented Jul 21, 2016 at 15:35
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\$\begingroup\$ What Dave said. Spotwelding (many sorts to investigate, some can be done DIY) is reliable but ultrasonic welding may be used on certain cases, crimping probably most common. While I have not tried it I have considered a convenient termination method for such cases, take the wire, fold double, slip into thin (perhaps tinned) copper or brass tube and crush under a screw terminal. \$\endgroup\$– KalleMPCommented Jul 31, 2016 at 6:40
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Nichrome is very refractory- it melts at around 1400°C- so that's not a problem.
Both stainless steel and Nichrome have oxide layers that render them impossible to soft solder. It's possible to silver solder (braze) them with high temperatures (eg. a propane torch), silver solder and brazing flux but that's not a lot of use if you want to connect to a PCB since the stainless steel is not soft solderable (the silver solder itself is soft solderable, if I recall correctly).
Pressure contact is one possibility (a terminal strip or a threaded stud) or you could spot weld or silver solder the Nichrome wire to a copper wire that could then be soft soldered.
answered Jul 21, 2016 at 13:26
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\$\begingroup\$ Spehro...I've had very good results soldering stainless steel. As I remember, I used a little dilute hydrochloric acid for flux, but "acid" flux solder might work as well. Clean the joint well. Never tried Nichrome \$\endgroup\$ Commented Jul 21, 2016 at 14:29
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\$\begingroup\$ Also, I don't think the solder alloy has any affect, only the flux. \$\endgroup\$ Commented Jul 21, 2016 at 16:10
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\$\begingroup\$ @RobertEndl Sure. You also can get special solder/flux for stainless steel from (for example) McMaster. It works okay, not as nice as bright copper. I was just trying to simplify it for the OP- regular fluxed solder won't work at all. Of course if the OP tries HCl, it needs to be thoroughly cleaned afterward as it's corrosive and ionic (so it will conduct and can cause severe problems). \$\endgroup\$ Commented Jul 21, 2016 at 16:11
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\$\begingroup\$ P.S. Acid core (plumbing solder) apparently uses analine hydrochloride, at least Kester's stuff does. It's reportedly also hygroscopic so it will absorb moisture from the air to cause electrical problems if traces remain. \$\endgroup\$ Commented Jul 21, 2016 at 16:19
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\$\begingroup\$ HCl flux is not something you want to use everyday. But, it can't be much worse than water-soluable flux. \$\endgroup\$ Commented Jul 21, 2016 at 20:00