Novel Epoxy Compositions for Microelectronic Packaging Applications

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.