Investigation of Wettability of Lead Free-Solder on Bare Copper and Organic Solder Preservatives Surface Finishes
International Journal of Materials Science and Applications
Volume 4, Issue 3, May 2015, Pages: 165-172
Received: Apr. 8, 2015;
Accepted: Apr. 20, 2015;
Published: Apr. 30, 2015
Views 4838 Downloads 205
Gabriel Takyi, Department of Mechanical Engineering, Kwame Nkrumah University of Science & Technology, Kumasi, Ghana West Africa
Peter Kojo Bernasko, Electronics Manufacturing Engineering Research Group, School of Engineering, University of Greenwich, Chatham Maritime, Kent, UK
Wettability plays an important role in the integrity of solder joints especially in critical safety operations. It helps in attaining successful soldering and reliable solder joints. The angle of wettability determines the degree of solder contact and strength of the solder joint. Moreover, the contact angle between the solid substrate and the molten solder determines the interconnection reliability. This paper focuses on the wettability of lead free solder on OSP and bare copper substrate surface finishes. The wetting behaviour of lead free solder pastes on bare copper board and Organic Solderability Preservatives (OSPs) substrates were investigated. The test vehicles consist of FR4 PCB single sided 100% copper clad with a thick film metallization and FR4 PCB single sided OSP. The substrate dimension was 100 mm×160 mm×1.6 mm. A total of 480 bumps of Lead-free solder pastes (96Sn-3.8Ag-0.5Cu and 96.5Sn-3.0Ag-0.7Cu alloy composition) were deposited for the investigation. The printing parameters and their values for the experiments include print gap of 0 mm, squeegee speed of 20 mm/s, pressure of 8kg and separation speed of 3 mm/sec. The pastes are screen printed on the substrates using 0.125mm thick stencil mounted on DEK 260 series printing machine. After the stencil printing process, the solder bumps deposited on the substrates were reflowed using a Novostar 2000HT horizontal convention reflow oven with 4-stage (preheat-soak-reflow-cooling). The FTA188 Analyser was employed for measuring the angle of contact between the substrates and the bumps. The results showed that the wetting contact angle of copper surface finish is lower as compared to the organic solderability preservatives surface finish and the wetting angle decreases as the contact surface area increases.
Peter Kojo Bernasko,
Investigation of Wettability of Lead Free-Solder on Bare Copper and Organic Solder Preservatives Surface Finishes, International Journal of Materials Science and Applications.
Vol. 4, No. 3,
2015, pp. 165-172.
Fu, Chun-Chong and Che, Chih-chi., 2011, Investigations of wetting properties of Ni-V and Ni-Co alloys by Sn, Sn-Pb, Sn-Cu and Sn-Ag-Cu solders, Journal of the Taiwan Institute of Chemical Engineers, 42, pp.350-355.
Passerone, A., Ricci, E., R. Sangiogi, R., J, 1990, Effect of metal purity and testing procedure on surface tension measurements of liquid tin, Material Sci. 25, 4266.
Wu, C. M. L., Yu, D. Q., Law, C. M. T. and Wang, L., 2004, Properties of lead-free solder alloys with rare earth element additions. Materials Science and Engineering, R 44. Pp.1-44.
Zang, L., Yuan, Z., Zhao, H. and Zhang, X., 2009, Wettability of molten Sn-Bi-Cu solder on Cu substrate, Material Letters, 63, pp.2067-2069.
Zeng, Q., Guo, J., Gu, X., Zhao, X. and Liu, X., 2010, Wetting Behaviours and Interfacial Reaction between Sn-10Sb-5Cu High Temperature Lead-Free Solder and Cu Substrate. Journal of Materials Science and Technology, 26(2), pp.156-162
Chang, T., Hsu, Y., M., Wang, M., 2003, Enhancement of wettability and solder joint reliability at the Sn-9Zn-0.5Ag Lead-free solder alloy-Cu interface by Ag precoating, Journal of Alloys and Compounds 360, pp.217-224.
Amore, S., Ricci, E., Borzone, G. and Novakovic, R., 2008, Wetting behaviour of lead-free Sn-based alloys on Cu and Ni substrates, Material Science and Engineering, A 495, pp.108-112.
Wei, X., Huizhen H., Zhou, L., Zhang, M. and Liu, X., 2007, On the advantages of using a hypoeutectic Sn-Zn as lead-free solder material, Materials letters. 61. pp.655-658.
Laurila, T., Vuorinen, V., Paulasto-Krockel, M., 2010, Impurity and alloying effects on interfacial reaction layers in Pb-free soldering, Material Science and Engineering, R 68, pp.1 38.
Sobczak, N., Kudya, A., Nowak, R., Radziwill, W., Pietrzak, K., 2007, Factors affecting wettability and bond strength of solder joint couples, Pure Appl. Chem., Vol. 79, N0. 10, pp. 1755-1769.