ICSR (Soldering and Reliability) Conference Proceedings


Authors: Heather McCormick, et al.
Company: Celestica Inc.
Date Published: 5/22/2009   Conference: ICSR (Soldering and Reliability)

Abstract: Package on Package components are becoming increasingly popular in electronic assemblies as a result of their extremely efficient use of board real estate. While this is particularly important in handheld portable applications, it is entirely likely that PoP components will see increasing uses in other types of electronic assemblies where space is at a premium. As a result, a full understanding of the reliability of PoP components in thermal cycling is essential, including assessing the impact of different possible assembly variations on reliability.

In this study, several assembly variations were studied, including fluxes, solder paste, component ball alloy, underfill material, and underfill pattern. Three different dippable fluxes and three different dippable solder pastes were selected for inclusion in the study, one from each of three different suppliers. In addition, three different combinations of component ball alloy were studied: SAC305, SAC405, and a version with a SAC105 top package, and a SAC125Ni bottom package. Selected assemblies were underfilled using one of two different underfill materials. For each underfill, some assemblies were filled on the lower level of joints only, and others were underfilled at both the top and bottom levels of joints.

Assemblies were subjected to thermal cycling from -40°C to 125°C to assess the reliability of the different assembly variations. Final results of the thermal cycling are presented, and preferred assembly methods based on quality and thermal cycling performance are discussed.

Key words: Package on Package, Dip Flux, Dip Paste, Reliability

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