120C will be problem for capacitors, specialy electrolytic.
Maybe with gas sterilization Chlorine Dioxide.
or
Ethylene Oxide (ETO) Sterilization
Ethylene oxide (ETO) was first reported in 1859, and gained industrial importance in the early 1900s. ETO sterilization for the preservation of spices was patented in 1938. The use of ETO evolved when few alternatives existed for sterilizing heat- and moisture-sensitive medical devices.
**broken link removed**
Think about to complete put PCB into some epoxy as box, to reduce potential surface for hiding some unwanted material. That will also help in sterilization proces, if you have flat and smooth surfaces. That will explude PCB parts repairing capability, but bring better sterilization. Sometimes parts on PCB can works very long, long time before they die, and sometimes whole PCB is changed as module.
;-)