> The reliability problem could be solved only by replacing soldering with another method of making electrical connections during PCB assembly, e.g. thermal/ultrasonic welding of copper on copper, metal deposition in vacuum etc.
The whiskers are not related to soldering. Of course there are some soldering issues which facilitate whiskers but that's about it. Tin is a normal plating material so you can find whiskets in places which were not soldered.
The only reason for using tin is soldering. Tin is used because it is the only metal with the right melting temperature, neither too low nor too high.
When you do not use soldering, you do not need tin. While it is possible for whiskers to also form on other metals, the chances of this happening are negligible in comparison with tin.
So yes, the only reason for whiskers being a serious problem is the need to use soldering.
