As known, hardware developing impossible without
soldering iron.
With UmTRXv2 I found that was used very infusible solder paste.
As I understand it is due to compliance to Pb-free.
Please note that RoHS is not a requirement in Europe for telecom
equipment! So if you have a SMT factory that still uses solder with Pb,
you can avoid those issues.
You mean it's a requirement only for consumer electronics? Didn't know that.