I'm trying to make a vaporizer pipe as a hobby project. The idea is that when you inhale from it, air passes by a cartridge heater and then goes through some "herbs". A thermocouple is used to measure the temperature of the heating cartridge. A microcontroller will read out the thermocouple via the MAX6675 chip and control the power of the cartridge heater using PWM via a MOSFET, in order to keep the temperature stable at a desired value.

I bought:

  • Cartridge heater Watlow C1A-9602: 24 V, 30 W, 1/8" diameter, 1" length, alloy 800 sheath
  • Thermocouple Watlow 20CKFUA012A: Calibration type K, 1/8" diameter, 1/2" length, stainless steel 304 sheath

Can I solder the cartridge heater and the thermocouple together? Then heat will easily flow from the heater to the thermocouple and I get a very accurate and consistent temperature reading.

Cartridge heater and thermocouple

The solder must be able to withstand 250 °C (482 °F) without causing any possible problems for the user, since the user will breath the air that flows next to the solder.

What solder could I use for this? Or is this a bad idea? I looked at solder alloys on Wikipedia, but there are just too many options. Perhaps I could use the cartridge heater itself to melt the solder.

  • \$\begingroup\$ don't you want to measure the temperature of the heated air instead? \$\endgroup\$
    – jsotola
    Commented Feb 15, 2023 at 1:29
  • \$\begingroup\$ The obvious problem with soldering is that the solder will melt at less than 250 degrees C. Although Wikipedia has a long list, there are just a few types of solder commonly used in electronics; I think mostly just 60/40 lead (or 63/37 for some people but that's not a lot different) or a handful of different lead-free alloys that are also pretty similar to each other. \$\endgroup\$ Commented Feb 15, 2023 at 1:39
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    \$\begingroup\$ (I edited the comment) You would be looking for some special type of solder to withstand this. For a high-temperature permanent metal-to-metal attachment you could consider brazing or welding. Or you could just wrap some wire around both to hold them together, although the thermal contact won't be as good. \$\endgroup\$ Commented Feb 15, 2023 at 1:42
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    \$\begingroup\$ I think you will want to insert the heater into a hole in some kind of heatsink, which helps transfer the heat to the air. Then you can put the thermocouple in another hole in the same heatsink \$\endgroup\$ Commented Feb 15, 2023 at 1:44
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    \$\begingroup\$ Silver solder or (better) weld. You might want to avoid anything with cadmium in it, if those solders are still sold in your region. \$\endgroup\$ Commented Feb 15, 2023 at 2:21

1 Answer 1


It's best to use a "copper" block with 1/8 inch holes, precisely drilled or made by CNC (by some blokes CNC shop) and clamp these devices with "tiny" headless screws.


Unlike other metals, stainless steel is very difficult to solder. It has a thick oxide layer that prevents melted solder from sticking to its surface.

using a burner around wires probably not a good idea, either.

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    \$\begingroup\$ Any reason you put "copper" in quotes? \$\endgroup\$
    – Paul
    Commented Feb 15, 2023 at 16:50
  • \$\begingroup\$ @Paul well copper is better than aluminum and other materials. He probably want the best results, not sure if there is anything better than copper. \$\endgroup\$ Commented Feb 15, 2023 at 17:54
  • \$\begingroup\$ Alright, yeah, seems like a good idea. \$\endgroup\$
    – Paul
    Commented Feb 16, 2023 at 11:49

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