SMTA International Conference Proceedings

Effect Of Mixed Alloy BGA Reballing On Board Level Drop Test Reliability

Authors: Andrew Daya and S. Manian Ramkumar, Ph.D.
Company: Center for Electronics Manufacturing and Assembly Rochester Institute of Technology
Date Published: 10/13/2013   Conference: SMTA International

Abstract: As more components are becoming lead free and not available in the tin lead alloy, there is an industry wide interest when it comes to the reballing and the subsequent effects it has on the strength of those components. This is particularly true for legacy parts needed for military applications some of which use tin lead solder. There is cause for concern due to the potential mixing of alloys and the differences in reflow temperatures of the two different alloys. Additionally, there are unknown characteristics regarding the intermetallics that are formed due to the potential of mixed alloys.

In a previous research completed and published by the authors on BGA reballing, it was determined that BGAs could be reballed with mixed alloys and still maintain original, and in some cases, greater ball shear strength. Using SAC405 and 63Sn/37Pb as reballing alloys, significant factors on shear strength for the reballing process was determined. The factors were BGA base alloy, the reball alloy, and the interaction between those two factors. The Factor that was insignificant was reflow environment (Nitrogen or Ambient).

This paper will expand upon and analyze the effects of reballed BGA components assembled on a board level assembly. By means of impact and drop testing, the impact reliability of reballed components on a test vehicle will be determined. After testing, samples will be cross-sectioned to evaluate defects or abnormalities observed through the reballing process, as well as any changes that occur during shear and drop testing.

The results from this research will be evaluated and compared to results of the previous study in order to determine additional significant factors, specifically in the lead free reballing process. When the experimentation is completed, the combined goal of both studies is to determine the optimal factors that should be used in the creation of a robust process for BGA reballing.

Key Words: 

BGA reballing, impact reliability, lead free

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