Soldering of Reed Switches and Reed Sensors requires some care to ensure that these delicate devices are not inadvertently damaged. Damage could range from minor operate AT or magnetic sensitivity shifts that could cause wrong actuation distance than what was expected, to more major damage such as cracks in hermetic seal integrity which could cause early failure or to outright scrap of the devices.
Manual Soldering of reed switch leads may be required when using custom plastic housing with external cables. The reed switches need to cropped to the required length and then soldered to the cables. When soldering reed switches, some guidelines should be followed.
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. This is to improve the quality of the welding and soldering. In a Reed Switch, the coefficients of thermal expansion of the leads and glass are closely matched. But soldering heats the leads more quickly than the time it takes to seal the reed switch. The result is that this sort of sudden heating which causes metal expansion can loosen or crack the glass-to-metal seal.
In most cases, cables need to be soldered 2-3 mm from the seals. The manual soldering dwell on the reed switch leads should be restricted to less than 2 seconds. If this cannot be followed, a heat sink between the soldering point and the glass seal, is recommended, as temperature too, has a damaging effect on these delicate devices. When requesting for cropped reed switches soldered to cables, kindly follow tolerances shown here.