Indium and low temperature solder do not seem to create a resistance lower than 30-40 Ohms when a sputtered copper trace 500um wide x 22mm long x 200nm thick is connected to a copper PCB with Au coated sma's.
We have cleaned indium and solder in HCL, and tried annealing it onto the trace at 300C in an oven with air for 45 seconds. Any longer than this and the copper peels away from the substrate. The copper trace is on 3nm of chromium, in turn on top of 80um thick glass.
Any suggestions for a lower resistivity?
I've heard sputtering aluminum nitride onto glass, then copper on top, will create a thermal barrier that will protect Cu from peeling while annealed. Then flux can be used to draw low temperature solder onto the trace for low resistivity contact.
Thanks!
Best regards,
Hal
Deposit Indium or Gold thin films by vacuum evaporation for better electrical contacts.
Do I understand it right, that the copper traces on glass/sapphire should be somehow connected to another PCB (FR4?) with SMA connectors? I don't know the exact geometry, but how about wire bonding with aluminum or copper wire? Or flip chip bonding using anisotropic conductive adhesive or silver filled adhesive? Did you try standard SAC solder?
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