G4A01084C Datasheet, PDF (15/22 Pages) List of Unclassifed Manufacturers – MICROTEMP Thermal Cutoffs INTRODUCTION

Test samples should be x-rayed before and after the soldering operation. The size of the chemical
pellet should be measured with an optical comparator or a toolmaker’s microscope to verify that
no shrinkage has occurred during the soldering operation (see figure 11). The epoxy seal should
retain its size and shape and not discolor. If the chemical pellet or the epoxy have changed size as
a result of the soldering operation more heat sinking is required.
EPOXY SEAL
BARREL
SPRING
THERMAL PELLET
ISOLATED
LEAD
TRIP
SPRING
CASE &
LEAD ASSEMBLY
Figure 11
Welding Leads
The thermal cutoff leads may also need to be heat sinked during a welding operation (see figure
12). The same precautions and tests described in the soldering section should also be followed for
welded leads.
HEAT SINK HERE
148
WELD POINTS
Figure 12
To avoid damaging or welding internal parts, care should be taken that none of the welding current
is conducted through the TCO. A welding current of hundreds of amperes can weld the internal
parts together, resulting in the TCO failing to open.
TCO leads must be supported during the weld operation to prevent breaking the thermal cutoff
epoxy seal.