Journal of Materials Research

Rapid Communications

Elimination of Au-embrittlement in solder joints on Au/Ni metallization

M.O. Alama1, Y.C. Chana1 c1 and K.N. Tua2

a1 Department of Electronic Engineering, City University of Hong Kong, Kowloon Tong, Hong Kong

a2 Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, California 90095-1595

Abstract

Systematic experimental work was carried out to understand the mechanism of Au diffusion to the solder interface, and a novel method was proposed to eliminate Au embrittlement by circumventing the continuous layer of (Au,Ni)Sn4 at the solder interface. Contrary to the usual expectation, it was determined that utilization of a very thin Ni metallization in the Au/Ni/Cu under bump metallization (UBM) was an effective means of maintaining mechanical integrity of the solder joint. It was found that the out-diffusion of Cu during the aging period changes the chemistry and morphology of the intermetallic compounds at the interface.

(Received July 14 2003)

(Accepted September 08 2003)

Key Words:

  • Embrittlement;
  • Morphology;
  • Diffusion

Correspondence:

c1 Address all correspondence to this author.e-mail: EEYCCHAN@cityu.edu.hk

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