I rarely use lead free solder - my fav is 63/37 or 60/40. However recently the PCB in my A/C and Heat Pump started twinking out.?
After troubleshooting the obvious (connectors, sensors, relays) I surmised a cold solder joint. Careful inspection under a 30X jewelers loupe didn't reveal any obvious breaks or bad solder joints. But since I had taken it out I decided to re-solder every connection on the PCB. ?
I wasn't able to get good wetting with my workhorse soldering pencil. Instead, I noted that it only came up to about 275 degrees C when measured using a K type thermocouple - I have a new tip on order as it appears it has degraded over the years. Certainly still good for basic 60/40 solder but not satisfactory due to the heat I needed to transfer to many of the more substantial component connectors on the PCB and the obvious lead free solder. Even my more rugged Weller soldering gun struggled a tad.
So, if you suspect lead free solder, be prepared to crank up the temp to 325 C. or more. Am also now looking into a more versatile temperature controlled soldering pencil. ?I am posting this as I'm seeing more and more commercial PCBs with lead free solder.
Oh, the AC/Heat Pump works fine now.
