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Hello fellow engineers.

I am trying to make an electrical connection with some gold plating. The gold plating is shaped like a rectangle, with dimensions of 3mm x 1.5mm x 0.1μm thick. Here is what the part looks like, it's quite small.

My procedure is:

  1. Tin some 24 gauge stranded copper wire
  2. Apply flux to the gold pad
  3. Attempt to solder the wire to the pad

Every time I try to solder (using standard solder: 63% tin, 37% lead solder wire, flux core, 0.6mm diameter. the solder I used), I end up with a failed connection within one second of solder flow. What I mean by this is, all the gold seems to disappear, and I am left with an extra-tinned wire. I think what happens is the gold is absorbed into the solder, as Wikipedia states here.

I am wondering, how do you suggest I make a reliable electrical connection to this part?

Edit 1

Per comments: - Tip: Metcal STTC-144, with a MX-PS5200 PSU. I am not sure what temperature the tip is at during soldering. - Substrate: from the product description that the substrate is Si, with 0.3μm of SiO2, then 0.01μm of Cr, then 0.1μm of Au.

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    \$\begingroup\$ You're burning it away? What is the substrate? And what tip, iron, and temperature? are you using? Photos of the damage too. \$\endgroup\$
    – DKNguyen
    Jul 9, 2019 at 1:20
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    \$\begingroup\$ It says "bonding and soldering are easy" :P. If we can't help you get it soldered, you could always try conductive epoxy. \$\endgroup\$
    – TimWescott
    Jul 9, 2019 at 1:25
  • \$\begingroup\$ @DKNguyen I added all the information you requested. \$\endgroup\$
    – Intrastellar Explorer
    Jul 9, 2019 at 2:25
  • \$\begingroup\$ @TimWescott, thank you that is also a good backup plan! \$\endgroup\$
    – Intrastellar Explorer
    Jul 9, 2019 at 2:25
  • \$\begingroup\$ That tip isn't doing you any favours. It's both small and round for poor contact rather than large and flat. But 0.01um of Cr is real thin. I thought there would be something more under the Au but I guess not. \$\endgroup\$
    – DKNguyen
    Jul 9, 2019 at 2:28

1 Answer 1

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Gold dissolves in tin. There is an indium solder called "TIX". It requires a strong flux, "TIX flux". You can get it on Amazon.
enter image description here

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  • \$\begingroup\$ Thank you @Robert Endl, I just bought a TIX kit, ASIN B017L4EHCY. Will circle back on how it performs! \$\endgroup\$
    – Intrastellar Explorer
    Jul 9, 2019 at 1:41
  • \$\begingroup\$ This worked!! I think their antiflux is quite useful :) My method consisted of 1. thin wire (tinned with TIX solder), ~26 AWG stranded. 2. I placed the chip with the 0.1μm thick pads on the table. 3. I placed a thin strip of metal over the interdigitated electrodes, to protect them from solder spatter (I found antiflux too hard to work with in this case, lol). 4. I placed the tinned wire on the pad. 5. I applied flux to both the tinned wire and the pad. 6. I put a bit more solder on my iron (flat tip), and pressed it down, completing the solder! \$\endgroup\$
    – Intrastellar Explorer
    Jul 12, 2019 at 2:22
  • \$\begingroup\$ Thank you again @RobertEndl! \$\endgroup\$
    – Intrastellar Explorer
    Jul 12, 2019 at 2:23
  • \$\begingroup\$ Be sure to clean the flux off. I think the stuff is corrosive. \$\endgroup\$
    – Robert Endl
    Jul 12, 2019 at 6:34

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