Board Level Reliability Study of Next Generation Large Die Wafer Level Chip Scale Package StructuresAuthors: Timo Henttonen, Paul Mescher, Doug Scott, Han Park, YongJae Ko and Kevin Engel
Company: Microsoft and Amkor Technology
Date Published: 10/23/2018 Conference: IWLPC (Wafer-Level Packaging)
To solve the challenge of extending cyclic life without underfill, new WLCSP structures and materials have been proposed. This paper describes the investigation of some of these innovative solutions through motherboard assembly and board level reliability testing. The package variables consisted of two WLCSP structures utilizing ball support mechanisms and a Bismuth (Bi) bearing solder ball that is expected to increase fatigue life.
Packages were produced separately with each variable, along with legs that included both new packages and new alloy. The finished assemblies, along with a control leg of standard structure/solder, were subjected to drop testing and temperature cycling. Solder joint integrity was monitored in-situ to accurately identify duration to failure for Weibull analysis.
The results clearly show that this new generation of WLCSP structures can offer dramatically improved fatigue life without a significant sacrifice in drop reliability. This benefit should allow the use of WLCSPs in more challenging environments, as well as providing designers the option of using larger package sizes in existing mobile designs.
Wafer Level Chip Scale Package (WLCSP), board level reliability (BLR), temperature cycling, drop test, SACQ, SAC
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