Masters Abstracts (1996)

GURUMURTHY, CHARAN
(August 1996), PhD., IBM Microelectronics, Assembly Process Design, Endicott, NY

Email: charan@us.ibm.com

Warpage in Area Array Microelectronics

Area array devices (ball grid array and direct chip attach) are being increasingly used in industry due to the advantages they offer with regard to miniaturization, performance, yield, reliability, and cost. Typically, a microelectronic component/assembly is made up of a stack of different layers of material. The inherent thermal mismatch that exists between the various layers of the component/assembly leads to warpage (out-of-plane displacement) of the component/assembly. Non-uniform heating of the components and assemblies is another primary reason leading to warpage. Warpage in microelectronic components and their assemblies is in most cases unavoidable and by itself (in many cases) is harmless to the assembly. But when combined with other assembly factors, warpage can severely affect assembly yield and reliability. Hence, it is essential to attain a fundamental understanding of the warpage phenomena in order to develop tangible solutions to control the same. Generally speaking, warpage can be controlled by three factors; materials used, physical dimensions of the package/assembly, and the assembly process. This thesis provides a generic understanding of the impact of these factors on warpage of area array microelectronic components and assemblies. Design Of Experiment (DOE) techniques were utilized to ensure the efficiency of the experimental strategy that was adopted. A mechanistic approach using elastic behavior based beam theory was used throughout this research more to validate experimental results and to analyze the sensitivity of warpage to component and assembly parameters. This research also focused on revealing the underlying issues behind the warpage phenomenon during the rework of the BGA assemblies. It is anticipated that the results of this research would provide pragmatic solutions to contain warpage.