Solid-state growth kinetics of intermetallic compounds in Cu pillar solder flip chip with ENEPIG surface finish under isothermal aging

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal

7 Scopus Citations
View graph of relations

Author(s)

Detail(s)

Original languageEnglish
Pages (from-to)12617-12629
Journal / PublicationJournal of Materials Science: Materials in Electronics
Volume28
Issue number17
Publication statusPublished - Sep 2017

Abstract

Electroless Ni/electroless Pd/immersion Au (ENEPIG) constitutes a promising metallization to replace the conventional ENIG or Ni/Au for 3D IC integrated module and optoelectronic packaging. Different ENEPIG plating thicknesses with copper pillar solder joints are subjected to thermal aging at 150 °C to investigate the intermetallic compounds (IMCs) formation and growth. Due to low temperature solid-state bonding, both Pd and Au layers do not completely diffused into Sn matrix and participated in the interfacial reactions to form (Pd,Au)Sn4 IMCs phase. (Pd,Au)Sn4 IMCs based on PdSn4 phase with dissolved Au, exhibits high growth rate and substantial consumption of Sn from solder. Upon increasing the aging time, it is found that (Cu,Ni)6Sn5 IMCs and (Pd,Cu,Au)Sn4 phase form at interface and follows a diffusion control mechanism, which weakened the solder joint and caused brittle fracture in a die peel test. (Cu,Ni)6Sn5 IMCs growth rate increases with decreases Pd thickness. Therefore, the types of IMCs formation, growth rate, and reliability of Cu pillar joint strongly depend on bonding temperature, Au and Pd thicknesses, and solder volume. Based on this study, the authors recommend suitable ranges of Au and Pd layer thicknesses for reliable Cu pillar solder joints

Citation Format(s)

Solid-state growth kinetics of intermetallic compounds in Cu pillar solder flip chip with ENEPIG surface finish under isothermal aging. / Pun, Kelvin P. L.; Islam, M. N.; Cheung, Chee Wah; Chan, Alan H. S.

In: Journal of Materials Science: Materials in Electronics, Vol. 28, No. 17, 09.2017, p. 12617-12629.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal