Pan Pacific Symposium Conference Proceedings


Authors: Hugh Roberts, et al.
Company: Atotech USA Inc., LSI Corporation, and Amkor Technology
Date Published: 2/12/2009   Conference: Pan Pacific Symposium

Abstract: The rapidly expanding adoption of Pb-free initiatives has created challenges for the electronics industry. Perhaps no other facet of manufacturing is more impacted by these changes than the assembly sector. Solder alloys, as well as surface finishes for both package substrates and PWBs must meet the Pb-free requirements. As a result, many designers, fabricators, assemblers and OEMs are facing challenges in terms of maintaining and ensuring reliability of these assembled packages.

The paper summarizes the findings from a major ongoing project to evaluate the performance of several combinations of surface finishes and solder ball alloys for wire-bond BGA package applications. In this phase of the evaluation, high-speed ball shear testing was used as the primary methodology for examining 2nd level solder joint reliability. The solder alloys tested included eutectic SnPb, Sn-2.3Ag and SAC305. The concept of “point of inflection” was used to determine the selected shear speeds for each solder alloy; dependent upon a failure analysis screening that was also performed. The evaluation included high-speed shear testing conducted after ball attach, as well as after extended high-temperature storage conditions.

Results of the high-speed ball shear investigations include analysis of shear strength, total energy and failure mode. Performance comparisons are made relative to solder alloy, surface finish and test condition. All findings are discussed and conclusions are offered with respect to the performance of the various surface finishes and solder alloys and the reliability of the resultant solder joints under the selected test conditions.

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