The use environments of electronic assemblies and their impact on surface mount solder attachment reliability

Electronic assemblies are subjected to varying thermal environments during their operational life. Nine broad use categories are classified, and worst-case, but realistic, temperature extremes as well as maximum possible cyclic temperature variations are identified on an annual basis. For these temperature cycles, the annually occurring number of cycles and the dwell durations at the temperature extremes are estimated. Accelerated test conditions are suggested for these use categories. Given the use categories´ thermal cyclic conditions and the suggested accelerated test conditions, the test durations needed to prove reliability for different service lives and a range of acceptable cumulative failure probabilities are developed. The results are discussed in the context of the overall reliability of electronic assemblies. They are also discussed in the context of the realities and the limitations of accelerated testing and a combined analytical/experimental reliability approach is suggested