MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Improvement on Thermal Fatigue Properties of Sn-1.2Ag-0.5Cu Flip Chip Interconnects by Nickel Addition
Shinichi TerashimaYoshiharu KariyaMasamoto Tanaka
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2004 Volume 45 Issue 3 Pages 673-680

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Abstract

The thermal fatigue properties of Sn-1.2Ag-0.5Cu (in mass%) flip chip interconnect were improved by a small amount of nickel addition. The thermal fatigue resistance of SnxAg-0.5Cu flip chip interconnects was enhanced by addition of 0.05 mass%Ni, and Sn-1.2Ag-0.5Cu-0.05Ni had longer thermal fatigue life than Sn-1.2Ag-0.5Cu. Cracks developed near solder/chip interface for all the bumps tested. This crack propagation is mainly governed by the nature of the solders themselves because a strain concentrated area was similar for all the tested alloys independent of the chemical contents. From the microstructural observation, fracture in Sn-1.2Ag-0.5Cu-0.05Ni due to thermal strain was a mixed mode, both transgranular and intergranular. From SEM and TEM analyses, fine Ag3Sn and (Cu,Ni)6Sn5 formed network around Sn grains in the initial microstructure of Sn-1.2Ag-0.5Cu-0.05Ni solder. Sn-1.2Ag-0.5Cu-0.05Ni solder joint suppressed coarsening of Sn grains even after thermal fatigue test. Namely, thermal fatigue properties of the Sn-1.2Ag-0.5Cu-0.05Ni solder joint is correlated to its microstructure, and the joint had longer fatigue life in spite of its lower silver content of 1.2 mass% due to both fine Sn matrix in the initial state and suppression of Sn grain coarsening even after thermal fatigue test.

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© 2004 The Japan Institute of Metals and Materials
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