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My goal is to solder stainless steel electrodes to a PCB in order to make a device that can measure differential voltage measurements from a surface.

How do I attach stainless steel to a PCB to create a design like the one in this picture? Which soldering material/method would be best?

I am looking to make 10 units.

Example of PCB with 3 stainless steel soldered to the board

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  • \$\begingroup\$ Can you just use a gold plated PCB pad instead of the stainless steel? \$\endgroup\$
    – D Duck
    Commented May 30, 2023 at 19:59
  • \$\begingroup\$ Can you use acid core flux to first tin the electrode, then clean it to remove the acid flux, then solder that with rosin flux to the PCB? \$\endgroup\$
    – DKNguyen
    Commented May 30, 2023 at 20:09
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    \$\begingroup\$ My personal trick for soldering difficult metals is: rough them up with coarse sandpaper, douse them in flux (to prevent the oxide layer reforming), grab a big hot chunky soldering iron, put a big blob of solder on the iron 8nstead of the workpiece, then press it down firmly onto the rough, fluxed surface. I've found that the faster you can heat up the workpiece, the better the results have been. \$\endgroup\$
    – Sam
    Commented May 30, 2023 at 23:19
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    \$\begingroup\$ Are you building a one-off, a few, or a giant production run (i.e., thousands a month). Different production quantities have different best answers. Please edit your question to reflect how many you're going to need. \$\endgroup\$
    – TimWescott
    Commented May 30, 2023 at 23:45
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    \$\begingroup\$ Are you certain those are stainless and not nickel? it's hard to tell the two materials apart, but nickel is easier to solder. alternatively perhaps electroplate thick-enough gold or nickel onto the PCB and solder nothing. \$\endgroup\$
    – Jasen Слава Україні
    Commented May 31, 2023 at 4:09

1 Answer 1

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In general, steel can be soldered fairly easily, but most if not all stainless steels cannot. Normal electronics solder flux is completely ineffective at removing the tough oxide layer of stainless.

I see three alternatives:

  1. Physically mount the stainless steel parts, say into screw terminals. Easiest solution.
  2. Use acid-based flux to tin the back side of the electrode first, then clean well and install. May still need a special solder. Might be easier to install with hot-air, as heat won't transfer to it well from a soldering iron.
  3. Ultrasonic welding. This can "solder" a wide range of not-normally-solderable materials, but will be more costly and difficult than traditional soldering. Also the mass of the terminal will work against it vibrating quickly.
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  • \$\begingroup\$ would you recommend using regular steel electrodes as opposed to stainless steel? \$\endgroup\$
    – dinoswords
    Commented May 30, 2023 at 20:51
  • \$\begingroup\$ Would gold-plated stainless steel be a viable path to getting a soldered electrical connection? Apparently it is easy (as in no intermediate metal plating required) to gold plate stainless steel. \$\endgroup\$
    – Andrew Morton
    Commented May 30, 2023 at 21:15
  • \$\begingroup\$ @dinoswords: regular steel would rust very quickly. \$\endgroup\$
    – TimWescott
    Commented May 30, 2023 at 23:45
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    \$\begingroup\$ We used to use an acid flux called "Ruby fluid" to solder stainless. Taking a look at McMaster Carr, I see a flux specifically noted for stainless steel. I would recommend cleaning in boiling distilled water afterwards to get rid of the acid. \$\endgroup\$
    – electrogas
    Commented May 31, 2023 at 3:17
  • \$\begingroup\$ gold solders easily, so gold plating could be a path to soldering it but if you can get tin or zinc plated plated instead that may be a saving, as both of these base metals also solder easily. \$\endgroup\$
    – Jasen Слава Україні
    Commented May 31, 2023 at 3:59

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