Solder Joint Creep and Stress Relaxation Dependence on Construction and Environmental-stress Parameters
نویسندگان
چکیده
Creep strain is probably the most important time-dependent damage accrual factor affecting solder joint reliability. Under typical multi-hour loading conditions, creep-induced strain is a complex time per cycle, the system. function of solder metallurgical structure, solder temperature, loading applied stress, and the spring constant of the combined part/lead/board The complex system level creep-fatigue interactions involved in electronic part solder joints are shown to be a strong function of the relative stiffness ratio K, which is the ratio of the stiffness of the combined solder-lead system to the stiffness of the solder element by itself. For a leadless chip package, K is close to unity. For a compliant leaded package, typically in the 0.01 to 0.0001 range, Important environmental stress dependencies, including the effects of operating temperature, displacement amplitude due to thermal and mechanical cycling, and cyclic K is frequency of loading are investigated for different levels of K. Understanding the sensitivity of solder strain range to relative stiffness and these key environmental parameters is
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تاریخ انتشار 1997