The mechanical properties and electrical resistivity of a Cu-1.5Ni-0.3Si-0.03P-0.05Mg (PMC102M) leadframe alloy was investigated. The effect of thermomechanical treatments on the microstructures and properties of a leadframe alloy was analyzed. The leadframe alloy was received as hot rolled plates with 8mm thickness from the Poongsan Co. The solution treatment temperature, reduction ratio of cold rolling and aging temperature were varied to control the microstructure of leadframe alloy. The yield strength increased, while the electrical resistivity decreased with decreasing the solution treatment temperature, since the grain size decreased with decreasing the solution treatment temperature. The dislocation density increased with increasing the reduction ratio of cold rolling and resulted in finer size and higher volume fraction of precipitates. The yield strength increased with increasing the reduction ratio of cold rolling due to the work hardening effect from larger dislocation density. The yield strength increased with decreasing aging temperature due to the finer size and higher volume fraction of $Ni_2Si$ precipitates. The electrical resistivity decreased with decreasing aging temperature due to the decrease of solute content in Cu matrix. The increased reduction during cold rolling leads to a preferred orientation of grains, thus the yield strength was sensitivity dependent on the crystallographic orientation. The deformation texture was identified to be transition types of {110} <112> and {123} <412>. The yield strength in transverse direction is higher than longitudinal direction as a result of deformation texture. Based on the analysis of the relationships between microstructure and properties, two types of thermomechanical treatments were performed to enhance the properties of leadframe alloy. One type of thermomechanical process was aimed to refine the grain size through the overaging, cold rolling and recrystallization. This process improved strength to 540MPa and elongation to 15% by reducing the initial grain size to 5μm after recrystallization. Another type of thermomechanical process is to refine the precipitates through two-step aging process. This process increased the tensile strength to 640MPa and reduced the resistivity to $1.475\times10^{-8}$Ωm due to the finer size of $Ni_2Si$ precipitates. Two-step aging treatment was effective to enhance the properties of leadframe materials.
