Flip Chip Package-in-Package (fcPiP): A New 3D Packaging Solution for Mobile Platforms

A new chip scale package is developed for use in high end cellular handsets and mobile products. The package houses a Baseband device, a pre-packaged Memory device and an Analog device in a 3-high stacked Package-in-Package (PiP) configuration wherein the base band die is attached to a 4-layer 1-2-1 Build-up laminate substrate using flip chip interconnection and the Memory package and Analog die are interconnected to each other as well as to the substrate using wire bonding. The package represents the ultimate in integration, wiring density, high performance and miniaturization. The development of the package was accomplished through close co-working of multidisciplinary teams comprising packaging, design and device architecture. The paper describes the challenges in the development of the individual packaging technologies such as bumped wafer thinning, thin die flip chip attach and underfilling, low loop wire bonding and the integration of those technologies, such as flip chip and wire bonding on the same substrate, underfill and overmolding, and chip-package interactions in the form of parametric shifts in sensitive analog circuitry on the die. The assembly process, reliability and failure modes observed are described in detail including the eventual qualification of the package and its introduction into volume production.