It is well known that in surface mount technology
(SMT), thermal strains in electronic assemblies are
induced in the solder joints by the mismatch between the
coefficients of thermal expansion (CTE) of the
components, substrate and solder, both during their
processing and in service. Therefore, thermo-mechanical
damage is likely to occur in the solder and the principle
reliability hazard in SMT assemblies is the resulting
fatigue cracking of the solder fillet, caused by cyclic
thermal stresses. These stresses may be caused by both
cyclic variations in power dissipation within equipment
and by external environmental temperature changes. Most
work reported to date has focused on the effects of
environmental temperature changes, although for many
types of equipment power cycling may result in
significant stresses. The present paper describes the
experimental determination of the actual temperature
distribution in a chip resistor assembly when it is
powered. The paper also discusses the significance of
such experimentally determined non-uniform temperature
distributions in electronic assemblies to fatigue damage
accumulation due to both power cycling and to cyclic
variations in the ambient temperature whilst the chip
resistor is powered. This fatigue damage accumulation
study is carried out using finite element analysis
