Abstract
A numerical method has been developed for calculating the thickness of intermetallic layers formed in substrate solder systems during the soldering process. As input, the method requires the temperature time profile for the soldering process and the isothermal liquid state growth rate parameters for the growth of the intermetallic layer. These usually consist of a growth constant, k sub(0), and an activation energy, Q. The method allows one to predict the thickness of a layer at any time during the soldering process. As such, it can be used in industrial solder processing to enhance the reliability and lifetime of solder joints by allowing control of the thickness of intermetallic layers. The validity of the method is demonstrated for intermetallic growth between copper and 62Sn-36Pb-2Ag solder. The kinetic parameters for the chosen model system were experimentally determined and isothermal intermetallic layer growth between molten solder and copper was found to follow a t super(0.25) dependence on time t. The growth rate increased with increasing temperature according to an Arrhenius dependence in the temperature range 187 to 258 degree C with Q identical with 7.04 kJ/mol and k sub(0) identical with 7.75 mu m/min super(0.25).