I attended a high-reliability soldering class while in the USAF. The attention to detail needed for a perfect solder joint is phenomenal. I had lots of good-loo

I attended a high-reliability soldering class while in the USAF. The attention to detail needed for a perfect solder joint is phenomenal. I had lots of good-looking joints get rejected for reasons such as exposed copper and a joint that had a convex surface. There is a USAF Technical Order for this, issued by the Navy and shared with the Marine Corps: https://www.robins.af.mil/Portals/59/documents/technicalorders/00-25-259.pdf https://www.robins.af.mil/Portals/59/documents/technicalorde... Cleaning the joint before and after was key. We used isopropyl alcohol in a push-down dispenser bottle, and acid brushes where we cut the bristles down to about 1/4" inch. Another poster asked about lead-free solder, and the military is using it now but has concerns over tin whiskers.