SMTA International Conference Proceedings


Effect of Solder Paste and Flux Type On Board Level Reliability of a 3D Wafer Level Chip Scale Package

Authors: Fei Xie, Ph.D., Daniel F. Baldwin, Ph.D., Paul N. Houston, and Brian J. Lewis
Company: Engent, Inc.
Date Published: 10/14/2012   Conference: SMTA International


Abstract: 3D packaging trend has currently come to the forefront packaging techniques as the drive to higher performance, smaller components and lower cost continues. The integration technologies of a 3D Wafer Level CSP packaging with the first level assembly process has been previously introduced. This paper focuses on the second level assembly process development and reliability performance assessment of the 3D WLCSP packages.

Robust yield and solid reliability performance were indicated for the second level assembly process under various conditions and in a 5000 air-to-air thermal cycle (-40?C to 125?C) testing on assembled packages. The impact of select solder pastes, flux types and different underfill methodologies on overall reliability are discussed in this paper, the detailed analysis for the different failure modes and root causes will be addressed. In addition, the best solder paste and underfill were selected after comparing the second level reliability results. Combined with the previous first level yield and reliability results, the reliability assessment on the second level package assembly shows that the structured 3D-WLCSP packages can be fabricated with robust yields and demonstrate high reliability.

Key Words: 

3D Wafer Level CSP (WLCSP), Solder paste, Assembly process, Second level reliability, Failure mode



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