Wetting Kinetics and Joint Strength of Sn-0.3Ag-0.7Cu Lead-Free Solder Alloy on Copper Substrate as a Function of Reflow Time

Abstract:

Solder plays a vital role in the interconnection of electronic devices in electronic assemblies. As an interconnection material, the solder joint executes electrical, mechanical and thermal functions. The use of lead bearing solders in electronic products is banned due to the toxicity and environmental risks coupled with lead. In the present study, wetting kinetics, interfacial reactions and the formation of intermetallic compounds (IMCs) during solidification of Sn-0.3Ag-0.7Cu solder alloy on Cu substrate and the corresponding joint strength were studied as a function of reflow time. Experiments were carried out at various reflow times of 10, 100, 300 and 500s. The reflow temperature was maintained at 270°C. The solder alloy showed enhanced wettability on the substrate at longer reflow times. The thickness of IMC layer formed during a reflow time of 10s was 1.67μm and the thickness increased to 2.20μm, 2.85μm, 2.91μm during 100s, 300s and 500s of reflow time respectively. The joint shear test was performed to assess the integrity of Sn-0.3Ag-0.7Cu solder solidified on Cu substrates using Nordson DAGE 4000 Plus bond tester. The joint strength increased with the increase in reflow time up to 300s and the maximum joint strength was observed for samples reflowed for 300s. Although the samples reflowed for 500s samples showed good wettability, they exhibited lowest joint strength.

• Periodical: Materials Science Forum (Volumes 830-831)
• Pages: 286-289
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.830-831.286
• Online since: September 2015
• Authors: Mrunali Sona, K. Narayan Prabhu
• Keywords: Joint Strength, Lead-Free Solders, Reflow Time, Wetting Kinetics

References

[1] H.T. Lee, H.S. Lin, C.S. Lee, P.W. Chen, Reliability of Sn-Ag-Sb lead-free solder joints, Mater. Sci. Eng. A. 407 (2005) 36-44.

DOI: 10.1016/j.msea.2005.07.049

[2] S.M.L. Nai, J. Wei M. Gupta, Effect of carbon nanotubes on the shear strength and electrical resistivity of a lead-free solder, J. Electron. Mater. 37 (2008) 515-522.

DOI: 10.1007/s11664-008-0379-6

[3] H. Jiang, K. Moon, C.P. Wong, Recent advances of nano lead-free solder material for low processing temperature interconnect applications, Microelectron. Reliab. 53 (2013) 1968–(1978).

DOI: 10.1016/j.microrel.2013.04.005

[4] Information on http: /alpha. alent. com/media/Files/CooksonElectronics/Effect%20of%20silver %2 0in%20common%20leadfree%20alloyspaperEng042309.

[5] N. Mookam, K. Kanlayasiri, Evolution of intermetallic compounds between Sn-0. 3Ag-0. 7Cu low-silver lead-free solder and Cu Substrate during thermal aging, J. Mater. Sci. Technol. 28 (2012) 53-59.

DOI: 10.1016/s1005-0302(12)60023-1

[6] M. Berthou, P. Retailleau, H. Fremont, A. Guedon-Gracia , C.J. Davennel, Microstructure evolution observation for SAC solder joint: comparison between thermal cycling and thermal storage, Microelectron. Reliab. 49 (2009) 1267–1272.

DOI: 10.1016/j.microrel.2009.07.040

[7] M. Sona, K.N. Prabhu, The effect of reflow time on wetting behavior, interfacial reaction and shear strength of Sn-0. 3Ag-0. 7Cu solder/Cu joint, Proceedings of SMTA ICSR-(2014).

DOI: 10.1007/s10854-014-1749-x