Single-joint shear strength of micro Cu pillar solder bumps with different amounts of intermetallics

Abstract This study investigates the effects of intermetallics (IMCs) on the single-joint shear strength of 50 μm diameter Cu pillar bumps joined with Sn–4.0%Ag–0.5%Cu (SAC405) solder caps. The correlations between the shear strength of the Cu pillar bumps and the IMCs aged at 180 °C for 150, 300, 500, and 750 h are studied. Microstructure characterization reveals that the Cu 6 Sn 5 morphology transforms from scallop-type to planar-type after 150 h of aging. Void formations are observed at the Cu 3 Sn/Cu interface after 300 h of aging and the amount of void formations increases with aging time. The shear test result shows that the shear strength decreases with aging time. Although the void formations did contribute to the deterioration of the solder joint strength, the main contributing factor was the planarization of the Cu 6 Sn 5 morphology through the aging process. The failure modes of the solder joint are also discussed in this study.

[1]  D. Kwong,et al.  Study of 15µm pitch solder microbumps for 3D IC integration , 2009, 2009 59th Electronic Components and Technology Conference.

[2]  K. Tu,et al.  Effect of electromigration on mechanical shear behavior of flip chip solder joints , 2006, Journal of Materials Research.

[3]  Weiqun Peng,et al.  Effect of thermal aging on the interfacial structure of SnAgCu solder joints on Cu , 2007, Microelectron. Reliab..

[4]  Seung Wook Yoon,et al.  Interfacial reaction and solder joint reliability of Pb-free solders in lead frame chip scale packages (LF-CSP) , 2000 .

[5]  I. Anderson,et al.  Elevated temperature aging of solder joints based on Sn-Ag-Cu: Effects on joint microstructure and shear strength , 2004 .

[6]  Hussein,et al.  Steep dispersion and group velocity below c/3000 in coherent population trapping. , 1996, Physical review. A, Atomic, molecular, and optical physics.

[7]  T. Mattila,et al.  Reliability of lead-free interconnections under consecutive thermal and mechanical loadings , 2006 .

[8]  C. Kim,et al.  Fatigue properties of lead-free solder joints in electronic packaging assembly investigated by isothermal cyclic shear fatigue , 2014, 2014 IEEE 64th Electronic Components and Technology Conference (ECTC).

[9]  Hao-Hsiang Chuang,et al.  Elimination of voids in reactions between Ni and Sn: A novel effect of silver , 2012 .

[10]  Jin Yu,et al.  Effects of residual S on Kirkendall void formation at Cu/Sn–3.5Ag solder joints , 2008 .

[11]  C. T. Lu,et al.  Abnormal Cu3Sn Growth and Kirkendall Formation Between Sn and (111) and (220) Preferred-Orientation Cu Substrates , 2011 .

[12]  Christopher Mark Johnson,et al.  Interfacial reaction in Cu/Sn/Cu system during the transient liquid phase soldering process , 2011 .

[13]  Edward Yi Chang,et al.  Accelarated Publication: Evaluation of Cu-bumps with lead-free solders for flip-chip package applications , 2009 .

[14]  R.R. Tummala,et al.  SOP: what is it and why? A new microsystem-integration technology paradigm-Moore's law for system integration of miniaturized convergent systems of the next decade , 2004, IEEE Transactions on Advanced Packaging.

[15]  S. Balakrishnan,et al.  Copper die bumps (first level interconnect) and low-K dielectrics in 65nm high volume manufacturing , 2006, 56th Electronic Components and Technology Conference 2006.

[16]  M. Li,et al.  Effects of substrate metallization of solder/under-bump metallization interfacial reactions in flip-chip packages during multiple reflow cycles , 2003 .

[17]  F. Che,et al.  Impact of Thermal Cycling on Sn-Ag-Cu Solder Joints and Board-Level Drop Reliability , 2008 .

[18]  Young‐Chang Joo,et al.  Intermetallic Compound Growth and Reliability of Cu Pillar Bumps Under Current Stressing , 2010 .