Welding of reed switch leads to single strand wire may be required for certain high temperature applications or when the lead length of the reed switch is not sufficient for non-standard lead formations. The reed switches need to cropped to the required length and then welded to the wire or single strand cable.
The leads of a reed switch are composed of approximately 50% nickel and 50% iron. These leads are plated after assembly with either gold or tin to improve weldability and solderability. Welding is generally preferred to soldering because less heat travels to the seal area. The coefficients of thermal expansion of the leads and glass are closely matched, but welding and soldering heat the wire more quickly than the time it takes to seal the glass tube. The result is that this sort of sudden heating which causes metal expansion can loosen or crack the glass-to-metal seal.
When reed switch leads are to be welded, some care should be taken to ensure cracks in the glass to metal seals do not develop. It should also be noted that during the welding process, certain amount of magnetic field may develop, which could operate the reed switch and cause the high current to pass through it. This will most certainly weld the contact as well! It is always better to weld one lead before taking up the other. When requesting for welded reed switch assemblies, kindly follow tolerances as shown here.