how to solve soldering problem?
I soldered a lot but from some time,my problem is that after tinning the tip and putting in soldering paste(when needed), I get a layer of a sort of oxide or something,but that is not what bothers me. The big problem is that the solder is not tinning on surfaces (wires and component leads). what can be the cause?(i'm guessing the solder since the problems started after buying new solder)