Thermomechanical reliability characterization of a handheld product in accelerated tests and use environment

Thermomechanical reliability of electronics has commonly been studied by employing accelerated temperature cycling (ATC) tests. However, due to the localized heat dissipation in modern electronic devices, operational power cycling (OPC) is considered a more realistic testing alternative. In order to characterize the thermomechanical reliability of modern high-density electronics, the failure modes, mechanisms and lifetimes of a contemporary commercial handheld device were studied under the ATC and OPC conditions. The experimental measurements and finite element analysis (FEA) showed distinct differences in the thermomechanical response of the device component boards under the OPC and ATC conditions. The results from FEA showed that the interconnection deformations during the OPC test were mostly in the elastic region of the solder, whereas those during the ATC tests reached well into the plastic region. The inclusion of the product enclosure further emphasized this difference, as the enclosure restricted the thermal expansion of the component board during OPC testing. The experimental test results were consistent with the FEA results, as the device failed due to solder interconnection cracking under the ATC conditions within 18 days of testing, but those under the OPC conditions remained operational even after 460 days. Finally, FEA estimations suggest that even three times higher power dissipation levels compared to those found in contemporary handheld devices would result in many years of lifetime in OPC testing.