Effect of Au and Ni layer thicknesses on the reliability of BGA solder joints

Research output: Chapters, Conference Papers, Creative and Literary Works (RGC: 12, 32, 41, 45)32_Refereed conference paper (with ISBN/ISSN)peer-review

View graph of relations

Author(s)

Related Research Unit(s)

Detail(s)

Original languageEnglish
Title of host publicationProceedings - EMAP 2005: 2005 International Symposium on Electronics Materials and Packaging
Pages88-94
Volume2005
Publication statusPublished - 2005

Publication series

Name
Volume2005

Conference

TitleEMAP 2005: 2005 International Symposium on Electronics Materials and Packaging
PlaceJapan
CityTokyo
Period11 - 14 December 2005

Abstract

A systematic experimental work has been carried out to understand the mechanism of Au diffusion to the solder interface as well as to investigate the effect of An and Ni layer thickness on the reliability of BOA solder joint. BGA solder balls of Sn37wt%Pb has been bonded on BGA solder bond pads of Au/electrolytic Ni/Cu by reflowing at 225°C for 0.5 minutes. The thickness of the Ni layer was varied from 0.35 mm to 2.8 mm and the thickness of Au was varied from 0.1 mm to 1.3 mm. Solid state aging up to 1000 h at 150°C have been earned out to simulate the ultimate interfacial reactions during an operation life of electronics devices. Cross-sectional studies of interfaces have been conducted by scanning electron microscopy (SEM) equipped with an energy dispersive X-rey (EDX) analysis to investigate the intedacial reaction phenomena. Ball shear tests have been carried out to obtain the interfacial strength and to correlate with the interfacial reaction products. After the shear tests, fracture surfaces have also been investigated to understand the fracture modes. It has been found that Au-embrittlement in the BGA Sn-Pb solder joints on Au/Ni/Cu BGA bond pads can be reduced by using either a thin Au layer or a thin Ni layer in the tri- layer Au/Ni/Cu BGA bond pad While it is conceivable to obtain a reduction in Au embrittlement by using a thin An layer in the BGA bond pad, contrary to the usual expectation, it was determined that utilization of a very thin Ni metallization was an effective means to maintain mechanical integrity of the solder joint. It was found that the out-diffusion of Cu during aging period changes the chemistry and morphology of the IMCs at the interface. During aging at 150°C, the thin Ni layer facilitates Cu diffusion from the bond pad and the Cu changes the brittle continuous layer of (Au,Ni)Sn4 to a nodular-shaped AuSn4. New interfacial reaction products with the modified morphology change the scenario of Au-embrittlement at the BGA solder interface and thus improve the interfacial joint strength significantly. © 2005 IEEE.

Research Area(s)

  • Au diffusion, BGA, Interfacial reactions, Reliability, Solder joints, Ternary intermetallic compounds

Citation Format(s)

Effect of Au and Ni layer thicknesses on the reliability of BGA solder joints. / Alam, M. O.; Chan, Y. C.; Rufer, L.

Proceedings - EMAP 2005: 2005 International Symposium on Electronics Materials and Packaging. Vol. 2005 2005. p. 88-94 1598241.

Research output: Chapters, Conference Papers, Creative and Literary Works (RGC: 12, 32, 41, 45)32_Refereed conference paper (with ISBN/ISSN)peer-review