Dissolution of solids in contact with liquid solder

The dissolution rate of a solid metal such as Cu, in contact with molten solder can be calculated with the use of the Nernst‐Brenner equation. We describe how this equation should be correctly used in cases when the solder is in contact with both the base metal and any intermetallic compounds that have formed. We also show that the concentration of solute in the solder will generally lie between the metastable solubility limit and the equilibrium solubility limit, illustrating these ideas with reference to a system comprising Nb as the base metal and eutectic In‐Sn as the solder, where the concentration levels can be directly correlated to the crystal growth rate.