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Indexed by:期刊论文

Date of Publication:2015-03-01

Journal:JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY

Included Journals:SCIE、EI、ISTIC、CSCD

Volume:31

Issue:3

Page Number:252-256

ISSN No.:1005-0302

Key Words:Size effect; Lead-free solder; Interfacial reaction; Intermetallic compound; Sn-3.0Ag-0.5Cu; Electroless nickel electroless palladium immersion gold (ENEPIG) pad

Abstract:Solder size effect on early stage interfacial intermetallic compound (IMC) evolution in wetting reaction between Sn-3.0Ag-0.5Cu solder balls and electroless nickel electroless palladium immersion gold (ENEPIG) pads at 250 degrees C was investigated. The interfacial IMCs transformed from initial needle-and rod-type (Cu, Ni)(6)Sn-5 to dodecahedron-type (Cu, Ni)(6)Sn-5 and then to needle-type (Ni, Cu)(3)Sn-4 at the early interfacial reaction stage. Moreover, these IMC transformations occurred earlier in the smaller solder joints, where the decreasing rate of Cu concentration was faster due to the Cu consumption by the formation of interfacial (Cu, Ni)(6)Sn-5. On thermodynamics, the decrease of Cu concentration in liquid solder changed the phase equilibrium at the interface and thus resulted in the evolution of interfacial IMCs; on kinetics, larger solder joints had sufficient Cu flux toward the interface to feed the (Cu, Ni)(6)Sn-5 growth in contrast to smaller solder joints, thus resulted in the delayed IMC transformation and the formation of larger dodecahedron-type (Cu, Ni)(6)Sn-5 grains. In smaller solders, no spalling but the consumption of (Cu, Ni)(6)Sn-5 grains by the formation of (Ni, Cu)(3)Sn-4 grains occurred where smaller discrete (Cu, Ni)(6)Sn-5 grains formed at the interface. Copyright (C) 2015, The editorial office of Journal of Materials Science & Technology. Published by Elsevier Limited. All rights reserved.