Evaluation of Reliability and Stack-Up Height on Next Generation 0.5 mm Pitch PoPAuthors: Mark Schwarz, Alan Choi, and Owen Fay
Company: Qualcomm Inc.
Date Published: 10/16/2011 Conference: SMTA International
The lower package is 14 mm in size, uses a 0.4 mm bottom pitch with 904 solderballs. The top package is also 14 mm, with a 0.5 mm pitch with 240 solderballs. The interconnect between the packages are joined through soldered connections embedded within vias of the bottom package’s mold compound. Three bottom solderball diameters were characterized as a drop-in solution to decreasing overall package thickness. Selected package configurations were evaluated based on drop shock, thermal cycling, and cyclic bend reliability test; focusing on both the bottom and top POP interface. Two mold compound via dimensions and two topball solder alloy compositions, Sn3.0Ag0.5Cu (SAC305) and Sn1.2Ag0.5Cu/0.05Ni (SAC125/Ni), were also studied for their effect on total collapsed height and reliability.
The intent of this study is to understand how different assembly variations affect the final assembled structure and board level reliability in order to determine which methods are realistic options for this next generation POP configuration. Package designs in this study were subject to 200 mechanical drops at 1500g and 0.5 ms, 1000 thermal cycles from -40°C to 125°C, and, when tested, 100,000 cyclic bends at 2 mm amplitude with a 1 Hz frequency. Coplanarity and high temperature warpage for the various configurations was also monitored.
Package on Package, POP, Height Reduction, Temp Cycling, Solder Alloy Composition
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