Special Seminar: Effect of Nanoparticle Addition on Interfacial Intermetallic Compounds between Lead Free Solder and Copper Substrate

Abstract

Restrictions on the use of lead in electronic products have prompted intense research activities on lead-free solders in recent years. Currently, tin based alloys are considered as potential replacements for lead bearing solders in many applications. However, the reliability of Sn based solders still remains a major concern.  Efforts are therefore underway to improve the properties and performance of Sn based solders. One of the approaches that researchers adopted to achieve this is through the addition of reinforcing particles to solder alloys.  Current trend towards the reduction of interconnection pitch size driven by the miniaturization of electronic devices encourages research on nanoparticle reinforcement.
In this presentation, our experience with the addition of two types of nanoparticles, viz., cobalt and molybdenum on the interfacial characteristics between Sn-3.8Ag-0.7Cu solder and copper substrate will be discussed. In the course of our study, we found that Co nanoparticles alter the morphology of the interfacial intermetallic compounds (IMC) from a scallopped type to a planar type.  They substantially suppress the growth of Cu3Sn but enhance that of Cu6Sn5.  The addition of Co nanoparticles greatly reduces the interdiffusion coefficient in Cu3Sn. Molybdenum nanoparticles, on the other hand, reduce the thickness and the diameter of Cu6Sn5 scallops, but do not alter their morphology.  Mo nanoparticles also suppress the growth of Cu3Sn. Mechanisms through which these two types of nanoparticles exert their infuence on the IMC were investigated.  Co nanoparticles undergo dissolution during reflow.  They get dissolved in Cu6Sn5 affecting its thermodynamic stability.  Thus Co nanoparticles exert their influence through alloying effect.  On the other hand, evidence shows that Mo nanoparticles remain intact as discrete particles.  They preferentially adsorb on the growth front of IMC and block the diffusion path of reactants, thereby suppressing IMC growth.

Bio

EDUCATION
•    Ph. D., Catholic University of Leuven, Belgium, 1992
•    M. Sc. Metallurgical Eng., Bangladesh University of Engineering and Technology (BUET), Dhaka, 1986
•    B. Sc. Engineering (Metallurgical), BUET, Dhaka, 1984.
EMPLOYMENT
•    Professor, Mechanical Engineering Dept., University of Malaya, Kuala Lumpur, December 2006 - present.
•    Professor, Materials and Metallurgical Engineering Dept., BUET, Dhaka, 2000 - 2006.
•    Associate Professor, Materials and Metallurgical Engineering Dept., BUET, Dhaka, 1996 - 2000.
•    Assistant Professor, Materials and Metallurgical Engineering Dept., BUET, Dhaka, 1987 - 1996.
•    Lecturer, Metallurgical Engineering Dept., BUET, Dhaka, September, 1984 to April, 1987.
CURRENT AREAS OF RESEARCH INTEREST
•    Electronic packaging materials
•    Electrodeposition and characterization of nanomaterials
•    Materials degradation

Note: This talk is not part of the MSE or WE 795 seminar series.