Authors: Mark Schwarz, Alan Choi, Owen Fay, and Milind Shah Company: Qualcomm Inc. Date Published: 10/16/2011
Abstract: Package on package (POP) technologies are advancing to finer pitches to account for technology advances in mobile applications along with leaving memory flexibility to the customer. As POP technology advances to finer pitches, more emphasis is placed on the top and bottom packages to reduce the overall height, physical dimensions, and package complexity. An area of main concern is for the top package pitch reduction moving away from 0.5 mm to 0.4 mm to achieve the desired POP package. This paper discusses the technical achievements developed for 0.4 mm POP SMT builds as it relates to reflow conditions along with warpage characteristics. We also discuss the development of the 0.4 mm bottom package in relation to top ball processing by means of laser ablation and associated solder attached to the top package. We also provide information on 0.4 mm SMT build characteristics and the associated board level reliability (BLR) for the combined package. The BLR data includes temperature cycling of -40°C to 125°C for 2000 cycles at 10 minute dwells, 200 drop shocks, and 100,000 cyclic bend tests on JEDEC designed daisy chain boards.
0.4 mm pitch POP, Package on Package, Warpage, Coplanarity, Board Level Reliability