Abstract:

It has long been known that solder fatigue life under thermal cycling is difficult to predict because of the time-temperature dependent creep behavior of solder material.  A unified theory of creep-fatigue damage, such as the Halford-Manson strain-range partitioning method, has the potential capability for examining the effects of time and temperature on fatigue life.  This study explores the utility of finite element methods in generating the strain-range partitioning information necessary as inputs for such a generic damage analysis.  The strain-range partitioning information is obtained in this paper for complex joint geometries and for realistic visco-plastic solder constitutive behavior using nonlinear finite element methods.

A sample solder joint of axi-symmetric configuration, commonly found in leaded through-hole mounting technology, is analyzed.  The strain history is determined for constant-amplitude temperature cycling with constant dwells at upper and lower ends of the cycle.  Detailed strain histories are presented to illustrate strain amplitude, mean strain and residual strains.  The strain history is partitioned into the elastic, plastic and creep components.  Such partitioned strain-history information is essential in order to implement the Halford-Manson strain-range partitioning technique for analyzing the creep-fatigue damage accumulation in solder material.
 

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