Uniform, Flat, and Interfacial Void Free Deposits for Copper Pillar Applications
Authors: Erik Reddington, Matthew Thorseth, Yi Qin, Julia Woertink, Ryan Farrell, Mark Scalisi, Emily Banelis, Pedro Lopez-Montesinos, Brandon Sherzer, Zachary Baumer, Wataru Tachikawa, Jianwei Dong, Mark Lefebvre, and Jeffrey Calvert Company: Dow Electronic Materials, Advanced Packaging Technologies Date Published: 11/11/2014
IWLPC (Wafer-Level Packaging)
Abstract: Solder capped copper pillar architectures are a fast growing segment in advanced packaging applications due to improved input/output (I/O) density compared to solder bumping alone. The ideal copper plating chemistry for this application yields deposits with excellent uniformity, flat pillar shape, and a void-free intermetallic interface after reflow with solder. Development of this plating chemistry is a challenge for the materials supplier, as improvement in one attribute typically comes at the expense of another. Deposits that are uniform, flat, and have a microvoid free Cu/solder interface are entirely possible with the selection of an appropriate organic additive system. In this paper, the performance of a new acid copper plating bath capable of yielding all three attributes will be highlighted. The effects of current density and pillar diameter on uniformity, shape, and reliability of the deposits from the copper plating bath will be discussed.
Cu pillar, flip-chip, uniformity, high current density, intermetallic compounds