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

The objective of this work was to determine the cure kinetics of ViaLux(TM) 81 photo-dielectric dry film and to optimize its curing schedule for the f abrication of sequentially built up high density interconnect-printed wirin g boards. Photosensitive epoxy materials such as the photo-dielectric dry f ilm 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 revea led a two-peak curing mechanism, which could not be separated at lower heat ing rates. The activation energies for the two cure events, calculated usin g the Kissinger method, were found to be 129 and 124 kJ/mol, respectively. A cure-dependent activation energy was also determined using the isoconvers ional method, and a "model-free" approach was adopted to simulate the evolu tion of degree-of-cure under dynamic and isothermal conditions. The results suggest that cure cycles of approximately 15 min at temperatures above 165 degrees C can result in a degree-of-cure of 90% and above. This implies th at faster fabrication is possible with either rapid thermal curing equipmen t or continuous cure surface mount technology furnaces. (C) 2000 John Wiley & Sons, Inc.