RUI: Modeling Formation of Microstructure of Intermetallic Compounds During Soldering.

Saint Xavier University, Chicago IL

Investigators

Abstract

0080176 Umantsev This grant supports theoretical research at an undergraduate institution (RUI). Soldering involves the use of a molten filler metal to wet the surfaces of joints, leading to formation of metallurgical bonds between components. A typical example of this type of reaction has binary tin-base eutectic solder joining copper components. In order to assess accurately the mechanical strength of solder joints, it is necessary to understand the morphology of the intermetallic compound layer. Growth and microstructural evolution of an intermetallic compound layer between the substrate and the solder is the primary concern of this theoretical research. The present research will study the Cu6Sn5 compound growing between the copper-substrate and a molten tin-base alloy. Experimental observations show that growth of the intermetallic compound from the molten solder demonstrates complex dynamical behavior. The intermetallic compound layer grows from the molten solder in the form of scallops, as opposed to a planar interface morphology of compound layers grown from bimetallic solid state couples. Solidification of the solder and the reaction of the solder with the substrate cause surface undulations. The reasons for the scallop-type growth mode are unresolved. The research will consist of two thrusts. The first concerns the driving force for theinstability of intermetallic layers growing from molten solders and will try to resolve the physical reasons for its existence. The second thrust will involve computer simulations of microstructural evolution which complement the analytical work. The effect of different metals on the evolution of interfacial microstructures will be investigated in the liquid and solid states of lead-free as well as lead-tin solders. The objective is to develop a model that takes into account different aspects of the soldering reaction kinetics and reproduces different regimes of growth of the interfacial structure. This model will help predict the structure of a growing intermetallic layer and improve the design methodology for advanced lead-free solders where the amounts of solder and substrate are highly limited. %%% This grant supports theoretical research at an undergraduate institution (RUI). Soldering involves the use of a molten filler metal to wet the surfaces of joints, leading to formation of metallurgical bonds between components. A typical example of this type of reaction has binary tin-base eutectic solder joining copper components. In order to assess accurately the mechanical strength of solder joints, it is necessary to understand the morphology of the intermetallic compound layer. Growth and microstructural evolution of an intermetallic compound layer between the substrate and the solder is the primary concern of this theoretical research. ***