Free Solder Interconnect Reliability Outlook

Lead-Free Solder Interconnect Reliability Outlook 

As the preceding chapters have illustrated, lead-free solder interconnect reliability is an important, yet complex, subject. A significant amount of work has been carried out over the past decade, yet more challenges still remain. Some of the most pressing issues are outlined in the following. 

Work is also needed to further characterize the creep and fatigue behavior of the lead-free solder alloy. The interfacial interactions (including intermetallics formation and growth, and the formation of Kirkendall voids on various PWB surface finishes) and their impact on reliability also warrant further investigation (Ref 2-3). 

Further study is also needed on the ductile-to-brittle transition of the Sn-Ag-Cu alloy. Recent work (Ref 4) indicates a sharp transition in the 

Many years of research points to compressive stresses as the underlying driving force for the formation and growth of tin whiskers. The compressive stress may arise from metallurgical interactions, thermomechanical factors, and/or mechanical processes. A recent nano-indenta-tion study (Ref 5-6) suggests that the stress field, including the level of the compressive stress, as well as the stress gradient, needs to be considered. 

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Lead-Free Solder Interconnect Reliability Outlook... 

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