Thermal and mechanical characterization of ViaLux(TM) 81: a novel epoxy photo-dielectric dry film (PDDF) for microvia applications

Multilayered high density interconnect (HDI) processing on organic substrates typically introduces warpage and residual stresses. The magnitude of the warpage and the residual stresses depends on, among other factors, the processing temperatures and the thermomechanical properties of the dielectric and substrate materials. In this work, a prospective epoxy-based dielectric material for such sequentially built up (SBU) high density-interconnect printed wiring boards (HDI-PWB) is considered. The polymer is a photo-dielectric dry film (PDDF) material called ViaLux^TM 81, which exhibits a complicated curing behavior due to the long lifetime of the cationic photoinitiators generated by ultraviolet (UV) exposure. The objectives of this work are: (i) to conduct differential scanning calorimetry (DSC) experiments and develop a cure kinetics model; (ii) to develop a cure shrinkage model based on thermal and chemical shrinkage experiments; and (iii) to determine the thermomechanical properties of partially and fully cured Vialux^TM 81 dry film. All of these experimental characterizations are necessary to select suitable process parameters and to obtain a consistent product with the desired physical and mechanical properties