THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING

GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Tuesday, April 6, 2021
10:00 AM 

via 

WebEx Video Conferencing 

https://gatech.webex.com/gatech/j.php?MTID=mfcea6c64e55124735b8323e5c9acace2

will be held the

DISSERTATION DEFENSE

for

Omkar Gupte

"Modeling, Design, and Demonstration of a Single, Innovative Metallurgical System for Socketable and Surface-Mountable Board Level Interconnections"

Committee Members: 

Prof. Rao Tummala, Advisor, MSE

Prof. Vanessa Smet, Co-advisor, ME

Prof. Preet Singh, MSE

Prof. C.P. Wong, MSE

Gregorio Murtagian, Ph.D., Intel Corporation

Abstract: 

OEM Microprocessors have conventionally been packaged using Land Grid Array (LGA) designs, press-fitted into sockets for ease of reworkability. However, Ball Grid Array (BGA) packages have recently become mainstream for surface mount (SMT) applications, driven by the need for miniaturization of electronic systems. While SMT processes and applications with BGA are becoming more widespread, the market need for sockets is also expected to increase significantly over the next decade. While microprocessor companies would benefit from producing a single BGA package design applicable in both socketing and SMT applications, this raises challenges for the OEM supply chain as no BGA-compatible socket is currently available. Enabling universal BGA packages compatible with both socketing and SMT processes is, therefore, critical to this industry transition.

Current BGA architectures are not compatible with socketing applications as the mechanical contact between the Au paddle and the solder sphere leads to undesirable reactions, increasing the contact resistance and degrading reworkability over time. To address this challenge, surface modification of BGA spheres with multilayered thin-film metallic coatings such as Ni-Au and Bi-Au is proposed to maintain a non-reactive noble metal interface when used in a socket. This presentation provides details of the studies conducted in this research, including (1) design, diffusion modeling, and finite element modeling of such coatings with a fundamental understanding of the trade-offs between SMT and socketing applications, (2) the development, characterization and optimization of the coating on solder spheres and attach processes using an in-house developed, hybrid sputtering/electroless deposition process and conventional mass reflow with solder paste, respectively, as well as (3) reliability characterization of the modified BGA packages in socketing and SMT applications. The results establish the proposed approach as a promising technology towards the development of a reliable, universal BGA solution.