Effect of thin gold/nickel coating on the microstructure, wettability and hardness of lead-free tin–bismuth–silver solder

This paper investigates the coating thickness and surface morphology of gold/nickel (Au/Ni) layer on copper (Cu) substrate. A cross-sectioned SEM analysis confirmed that the Au/Ni coating was uniform. The top Au layer with average thickness of 0.7 µm appeared to have a very smooth surface without any defect such as cracks and delamination. However, the thin Au/Ni coating greatly influenced the interfacial structure and material properties of electronic interconnections. In the reference Cu substrate/Sn–Bi–Ag solder system, an island-shaped Cu6Sn5 IMC layer at the interface could be clearly observed at the initial reaction stage. After a prolong reaction, a very thin Cu3Sn IMC layer was formed with excessive growth of the Cu6Sn5 IMC layer which can deteriorate the electronic interconnection life-span. However, in the Au/Ni coated substrate/solder system, a very thin scallop-shaped ternary Ni3Sn4 IMC layer formed without the Cu3Sn IMC layer, indicating that the Au/Ni coating hindered the growth of the IMC layer, which consequently changed the activation energies and refined the microstructure. Additionally, the overall micro-hardness of the Au/Ni coated substrate/solder system is higher than that of the reference solder system.

[1]  Liangchi Zhang,et al.  Growth mechanism of intermetallic compound and mechanical properties of nickel (Ni) nanoparticle doped low melting temperature tin–bismuth (Sn–Bi) solder , 2015, Journal of Materials Science: Materials in Electronics.

[2]  M. Sobhy,et al.  Tensile creep characteristics of Sn–3.5Ag–0.5Cu (SAC355) solder reinforced with nano-metric ZnO particles , 2014 .

[3]  André Van Calster,et al.  Processing quality results for electroless/electroplating of high-aspect ratio plated through holes in industrially produced printed circuit boards , 2005, Microelectron. Reliab..

[4]  M. Abtew,et al.  Lead-free Solders in Microelectronics , 2000 .

[5]  Samjid H. Mannan,et al.  A review: On the development of low melting temperature Pb-free solders , 2014, Microelectron. Reliab..

[6]  Yaowu Shi,et al.  Evaluation on the characteristics of tin-silver-bismuth solder , 2002 .

[7]  Tadashi Ariga,et al.  Physical properties of Sn58Bi–xNi lead-free solder and its interfacial reaction with copper substrate , 2015 .

[8]  S. Delsante,et al.  Synthesis and melting behaviour of Bi, Sn and Sn–Bi nanostructured alloy , 2015 .

[9]  King-Ning Tu,et al.  Structure and properties of lead-free solders bearing micro and nano particles , 2014 .

[10]  Asit Kumar Gain,et al.  Microstructure, mechanical and electrical performances of zirconia nanoparticles-doped tin-silver-copper solder alloys , 2016, Journal of Materials Science: Materials in Electronics.

[11]  Zuoan Li,et al.  Thermodynamic investigation of the Ag-Bi-Sn ternary system , 2008 .

[12]  Andrew A. O. Tay,et al.  Nanoindentation study of Zn-based Pb free solders used in fine pitch interconnect applications , 2006 .

[13]  P. Grant,et al.  Microstructural evolution at Cu/Sn–Ag–Cu/Cu and Cu/Sn–Ag–Cu/Ni–Au ball grid array interfaces during thermal ageing , 2014 .

[14]  Mingyu Li,et al.  Microstructure evolution, interfacial reaction and mechanical properties of lead-free solder bump prepared by induction heating method , 2016 .

[15]  I. Kaban,et al.  Experimental study of density, surface tension, and contact angle of Sn–Sb-based alloys for high temperature soldering , 2010 .

[16]  G. Zanicchi,et al.  Wetting behaviour and reactivity of lead free Au–In–Sn and Bi–In–Sn alloys on copper substrates , 2007 .

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

[18]  G. Dehm,et al.  Fracture toughness of intermetallic Cu6Sn5 in lead-free solder microelectronics , 2016 .

[19]  Guido Schmitz,et al.  Mechanical properties of Pb-free SnAg solder joints , 2011 .

[20]  G. Borzone,et al.  Wetting behaviour of lead-free Sn-based alloys on Cu and Ni substrates , 2008 .

[21]  Y. Chan,et al.  Electromigration in Sn-Ag solder thin films under high current density , 2014 .

[22]  Y. C. Chan,et al.  Failure mechanisms of solder interconnects under current stressing in advanced electronic packages , 2010 .

[23]  C. Chung,et al.  The critical oxide thickness for Pb-free reflow soldering on Cu substrate , 2012 .

[24]  Y. C. Chan,et al.  The influence of a small amount of Al and Ni nano-particles on the microstructure, kinetics and hardness of Sn–Ag–Cu solder on OSP-Cu pads , 2012 .

[25]  Y. C. Chan,et al.  Growth mechanism of intermetallic compounds and damping properties of Sn-Ag-Cu-1 wt% nano-ZrO2 composite solders , 2014, Microelectron. Reliab..

[26]  S. Delsante,et al.  Interfacial reactions in the Sb–Sn/(Cu, Ni) systems: Wetting experiments , 2012 .

[27]  V. Kripesh,et al.  Influence of single-wall carbon nanotube addition on the microstructural and tensile properties of Sn–Pb solder alloy , 2008 .

[28]  Nilgun Ciliz,et al.  Cleaner production application as a sustainable production strategy, in a Turkish Printed Circuit Board Plant , 2010 .

[29]  Y. C. Chan,et al.  Microstructure, kinetic analysis and hardness of Sn–Ag–Cu–1 wt% nano-ZrO2 composite solder on OSP-Cu pads , 2011 .

[30]  Fu Guo,et al.  Effect of rare earth element addition on the microstructure of Sn-Ag-Cu solder joint , 2005 .

[31]  Ping Liu,et al.  Effects of multiple reflows on interfacial reaction and shear strength of SnAgCu and SnPb solder joints with different PCB surface finishes , 2009 .

[32]  K. Suganuma.  Advances in lead-free electronics soldering , 2001 .

[33]  Lawrence H. Bennett,et al.  Binary alloy phase diagrams , 1986 .

[34]  Y. Chan,et al.  Effect of nano Ni additions on the structure and properties of Sn-9Zn and Sn-8Sn-3Bi solder in ball grid array packages , 2008, 2008 2nd Electronics System-Integration Technology Conference.

[35]  Y. C. Chan,et al.  Interfacial microstructure and shear strength of Ag nano particle doped Sn-9Zn solder in ball grid array packages , 2009, Microelectron. Reliab..