Soldering Thermo Couples

Let's talk a little about thermocouple wire alloys:

There are about 6 principal thermocouple pairs in common use:

• Type E - CR-CN
• Type J - Fe-CN
• Type K - CR-AL
• Type R - Pt/13/Rh-Pt
• Type S - Pt/10/Rh-Pt
• Type T - Cu-CN

Where,

• Cu == Copper
• CR == Chromel
• CN == Constantan (53%Cu, 45%Ni)
• Al == Alumel
• Fe == Iron
• Pt/10/Rh == Platinum + 10% Rhodium
• Pt/13/Rh == Platinum + 13% Rhodium
• Pt == Platinum

Each of these alloy combinations makes a dandy thermocouple, but each also has unique characteristics relative to soldering with conventional tin/lead solders, or welding.

• Type E won't solder
• Type J solders nicely
• Type K won't solder
• Type R won't solder
• Type S won't solder
• Type T solders nicely

Basically any alloy that has significant quantities of Chromium, Platinum, Rhodium, or Aluminum will be difficult to solder.

Copper solders nicely, iron solders nicely, nickel pretty well..,

-Chuck Harris