NDLI: Effect of Structural Design Parameters on Wafer Level CSP Ball Shear Strength and Their Influence on Accelerated Thermal Cycling Reliability

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Lakhkar, Nikhil Viswanadham, Puligandla Agonafer, Dereje
Copyright Year	2009
Abstract	Ball shear testing is typically conducted in Wafer level chip scale package (WLCSP) fabrication to estimate the strength of the solder ball attachment. Generally, the solder ball shear strength is dependent on the solder ball size, pad size, solder/pad interface treatment, reflow temperature and time. Solder ball strength is also a function of ram speed and height at which the ball is sheared with respect to the wafer. Recent investigations suggest that ball shear test is being used as an indicator for board level reliability of assemblies. In current market lead time for launching a new product is very short. Unfortunately, it takes several weeks to qualify a new product by board level qualification process. If there is a methodology through which one can predict the board level performance by extrapolating the wafer level test, it will save great amount of resources in testing and millions of dollars worth of testing time. In the first part of this study, we conducted a wafer level ball shear test. A DOE was created for varying wafer level structural parameters like solder ball size and type. Ball shear tests and Accelerated thermal cycling have similar failure signatures of compression on inner side and tension on outer side. Thus, for specific cases there is a possibility of correlating the two failure methodologies based on their failure signatures. Strain rate for ball shear test was determined based on shear speed and solder pad diameter. Strain rate for accelerated thermal cycling was determined based on difference in CTE between board and package. In this paper, results from ball shear test and accelerated thermal cycling are compared to find correlations for specific cases. The correlations derived from this study are statistical and empirical.
Starting Page	239
Ending Page	249
Page Count	11
File Format	PDF
ISBN	9780791843789
DOI	10.1115/IMECE2009-11832
e-ISBN	9780791838631
Volume Number	Volume 5: Electronics and Photonics
Conference Proceedings	ASME 2009 International Mechanical Engineering Congress and Exposition
Language	English
Publisher Date	2009-11-13
Publisher Place	Lake Buena Vista, Florida, USA
Access Restriction	Subscribed
Subject Keyword	Structural design Solders Compression Temperature Shear strength Semiconductor wafers Tension Manufacturing Reliability Shear (mechanics) Failure Testing
Content Type	Text
Resource Type	Article

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