Recommended · for advanced
Ultrasonic soldering bonds glass, titanium, stainless steel, ceramics, tungsten, nichrome...
Why people recommend it
Applied Science's video is the usual pointer when someone must bond to materials that resist ordinary solder, and it covers building an ultrasonic iron.
Watch for: Costlier and harder than conventional soldering
In their words
This can "solder" a wide range of not-normally-solderable materials, but will be more costly and difficult than traditional soldering.
rdtsc on electronics.stackexchange.com, May 2023. CC BY-SA.
