Abstract
Using proprietary epoxies, new formulations have been developed for use in microelectronic packaging applications. The key features of these formulations are short cure cycle, long term stability at 25° C, very low cure volatile, low moisture absorption, low coefficient of thermal expansion (CTE), excellent adhesion to various substrates. The CTE does not change appreciably with temperature between 0–200°C. This unique behavior is attributed to the interpenetrating network-like (IPN) structure of the base resins in the cured state. Further evidence of the IPN structure is the broad loss modulus and tan 6, observed between −150°C and −150°C, in dynamic mechanical tests. The extensive curing reaction in these catalyst-cured systems results in a highly crosslinked polymer network with good moisture resistance (< 0.2°o after 14 days in 85°C/85% RH) and thermal stability (< 0.3 wt % at 300°C of the cured material). Under 85/85 conditions, no appreciable changes in modulus was observed. Extent of cure studies in a dynamic scanning calorimeter (DSC) show a complete cure with no postcure requirements. Cure cycles for these formulations range from 1 hour at 140°C to about 1 minute @170°C. Currently, cure stresses, fracture toughness (bulk and interfacial), and various reliability tests are being performed to characterize the underfill, glob top encapsulants, and die-attach adhesives.
