Surface Mount International Conference Proceedings


DESIGN AND PROCESS OPTIMIZATION FOR 1.0 MM PITCH CCGA

Author: Marie Cole
Company: IBM Microelectronics
Date Published: 8/23/1998   Conference: Surface Mount International


Abstract: Ceramic Column Grid Array (CCGA) packages have become increasingly popular as an alternative to Ceramic Ball Grid Array (CBGA) packages for applications requiring more than 625 interconnections [l]. As package body size increases beyond 32.5 mm, the column structure offers an essential improvement to the thermal fatigue life of the package solder joint for many applications. Already in production are CCGA packages with 1.27 mm column pitch, providing more than 1000 interconnections in a 42.5 mm body size. Computer applications such as mainframes, midrange servers and high end work stations continue to drive increased silicon performance and signal count. Rather than continue to expand package body size, trends in miniaturization call for an increase in interconnect density to increase the number of package interconnects. Reducing the pitch to 1.0 mm increases the column count on a 42.5 mm CCGA package by 52% to 1657 columns. Although not as cost sensitive as commodity packages, CCGA packages must be high yielding and easily manufacturable through the ceramic and bond / assembly facilities in production volumes. In addition, to be considered a viable industry standard package technology, the card and assembly technologies must be straightforward and widely available. Optimization across all of these areas is essential and design tradeoffs among these elements must be analyzed in concert. With the established design groundrules and processes for 1.27 mm pitch CCGA as a base, this optimization for 1.00 mm pitch CCGA has been achieved. This paper will discuss the adjustments required to the chip carrier processes to accommodate the tighter pitch, the finer wiring and top surface groundrules required of the Printed Circuit Board (PCB) technology and the optimization of the card assembly and rework processes. This evaluation focuses both on yield and manufacturability aspects of the technology, as well as the reliability of the completed interconnection structures. The yield analysis of the various design options, along with the reliability of these variations will be discussed. The conclusion of this study results in the definition of optimized parameters to offer to customers for use in their new systems. keywords - Ceramic Column Grid Array, Fine Pitch Ball Grid Array, Card assembly reliability



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