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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.44  No.2 (2003)  >  pp.290-297

MATERIALS TRANSACTIONS
<<Previous article Vol.44  No.2 (2003)   pp.290 - 297 Next article>>

Effect of Under Bump Metallurgy and Reflows on Shear Strength and Microstructure of Joint between Cu Substrate and Sn-36Pb-2Ag Solder Alloy

Seung Wook Yoon1), Jong Hoon Kim2), Sang Won Jeong2) and Hyuck Mo Lee2)
1) Advanced Package Development Support, Institute of Microelectronics (IME)
2) Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology


The interfacial reaction between Sn–36Pb–2Ag (numbers are all in mass% unless specified otherwise) solder balls and Ni, Ag and Ni/Ag electroplated on a Cu substrate was investigated and the joint bonding strength was measured using a ball shear tester. The intermetallic Ag3Sn was observed at the interface of the Cu/Ag/solder joint and Ni3Sn4 was found at the Cu/Ni/solder joint. In the case of Cu/Ni/Ag substrate, the layer sequence was observed to be Cu/Ni/Ni3Sn4/Ag3Sn/solder. The Ag layer was completely consumed by formation of Ag3Sn but the Ni layer remained. Environmental tests showed that the Cu/Ni/Ag substrate retained better solder joint reliability than either Ni or Ag single plated Cu substrate. Two types of reflow profiles were tested and the specimen reflowed by a higher temperature profile showed a higher solder joint strength. Solder joint strength and microstructural change were observed with several reflow cycles in considering the real board mounting conditions. There was significant evolution of solder and joint microstructures with reflow cycles and it explained well the change of solder joint strength.


Keyword:
tin-lead-silver solder, under bump metallurgy, interfacial reaction, solder joint strength, joint microstructure, interfacial intermetallic compound

Received: August 05, 2002
Accepted: November 28, 2002 , Published online: September 06, 2005
Copyright (c) 2005 The Japan Institute of Metals

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