Influences of viscoelasticity of polybutylene terephthalate (PBT) on the thermal interface contact of LED spotlight module

The influence of viscoelastic behavior of polybutylene terephthalate (PBT) on reliability of the thermal contact of a spotlight module is evaluated. The contact between a module and the heat sink is evaluated using non-linear finite element model. The viscoelastic behavior of PBT was obtained under multiple frequencies from single cantilever DMA experiments. The relevant viscoelastic parameters (i.e. Relaxation time τ_i, Shear relaxation coefficient G_n and volume relaxation coefficient K_n) were obtained by using the linear regression. The mechanical behavior of the contact interface under high temperature storage was simulated. The simulation results agree with the experimental measurement. The proposed simulation is an efficient tool to depict the effect of PBT viscoelastic behavior on the reliability of LED spotlight module.