Investigation of the curing behavior of a novel epoxy photo-dielectric dry film (ViaLux? 81) for high density interconnect applications

Abstract

The objective of this work was to determine the cure kinetics of ViaLux™ 81 photo-dielectric dry film and to optimize its curing schedule for the fabrication of sequentially built up high density interconnect-printed wiring boards. Photosensitive epoxy materials such as the photo-dielectric dry film studied herein have complicated curing regimes. This is attributed to the long lifetime of the curing catalyst that is generated by ultraviolet exposure. Dynamic differential scanning calorimetry (DSC) experiments revealed a two-peak curing mechanism, which could not be separated at lower heating rates. The activation energies for the two cure events, calculated using the Kissinger method, were found to be 129 and 124 kJ/mol, respectively. A cure-dependent activation energy was also determined using the isoconversional method, and a “model-free” approach was adopted to simulate the evolution of degree-of-cure under dynamic and isothermal conditions. The results suggest that cure cycles of approximately 15 min at temperatures above 165°C can result in a degree-of-cure of 90% and above. This implies that faster fabrication is possible with either rapid thermal curing equipment or continuous cure surface mount technology furnaces. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 430–437, 2000