Relaxation Investigation for Terminals of Electronic Connectors Under Thermal Shock Test

Electronic connectors are in general required to pass specifications of the thermal shock test. The contact force of the terminal could decay gradually due to the stress relaxation effect under thermal loading conditions. A finite element analysis is conducted to examine the contact force variation of the terminal in the present study. Both a plug and a receptacle socket of mini USB are chosen for the investigation here. A mated socket pair is placed in the temperature-controlled chamber, and the associated electrical resistance is then measured on-line in certain periods based on the specifications of the thermal shock test. Experiments indicate that the electrical resistance rises slowly as the thermal cycle number increases. Viscoplasticity is adopted for the terminal material of phosphor bronze alloy in the numerical analysis. Stress-strain relations of the terminal at various temperatures are measured via the uniaxial tensile test. A power-law creep model with the strain-hardening form is selected to account for the relaxation behavior of the terminal. Corresponding parameters of the creep model are evaluated based on the uniaxial tensile relaxation test. Simulation results show that the decreased amount of the contact force is rather limited after ten thermal cycles. Relationships between the contact force and the electrical resistance increasing percentage are then investigated.