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|Design and Reliability of µPILR™ Package-on-Package (PoP)|
|Keywords: design, comparative analysis, reliability|
|Manufacturers are increasingly challenged to meet reliability, performance, form factor and cost objectives for today’s enhanced mobile electronics. 3D packaging is fast becoming the package design of choice to overcome the technical limitations of conventional interconnect technology. 3D packaging solutions are available in several forms, some of which are chip-stack, package-in-package (PiP) and package-on-package (PoP). Each version has its own advantages and disadvantages, with chip-stack and PiP offering smaller size and higher internal IO, and PoP offering greater yield and system flexibility. This paper will discuss the design possibilities of PoP for leading-edge, feature-rich mobile electronic applications. Future requirements such as chip size, IO, memory interface, etc., will be covered along with a discussion on features such as package size, thickness, interconnect pitch, yield impact, etc. The µPILR PoP technology is characterized by interconnection paths that enable high aspect ratio interconnects. For example, a stand-off distance (to clear the bottom chip) of 0.3mm, a 0.4mm pitch is possible for the top package. These same interconnects can also be used for the bottom package for easier routing of traces and/or finer pitch. A reference design study will be included to quantify the PoP characteristics. The µPILR PoP has been fabricated and tested for reliability. Assembly results have shown that the SMT yield at fine pitch is significantly higher as compared to that of conventional solder ball PoP. Thermal cycling and drop tests results show PoP to have high reliability, especially for drop tests. Hundreds of drop tests were performed before evidence of the first failure were captured. Failure analysis has shown that µPILR technology interconnect acts as a crack growth inhibitor and therefore increases the lifetime under dynamic loading. In conclusion, a design and reliability study of will be presented. Results of this study show that µPILR PoP technology meets industry requirements for miniaturization without compromising yield or reliability.|
|Ilyas Mohammed, Director, Packaging
San Jose, CA