Heat activatable adhesive for wire scribed circuits

Abstract

A non-blocking, solid, adhesive composition comprising, (a) a film forming polymeric resin of average molecular weight between 10,000 and about 100,000 and having an epoxide, hydroxyl or unsaturated functionality greater than about 2, the polymeric resin being selected from the group consisting of polyesters, polyurethanes and epoxies; (b) at least one filler, or at least one polyfunctional compound of average molecular weight below about 7,000 and containing a polyaromatic backbone, or mixtures thereof, the weight ratio of (a) to (b) being between about 1.5:1 and about 9:1; and (c) a curing agent which is capable of cross-linking and curing the polymeric resin to a C-stage, the curing agent being present in an amount sufficient to C-stage the polymeric resin. The adhesive composition can be activated without becoming C-staged upon application of sufficient heat or ultrasonic energy for a time period less than one second. The curing agent is non-reactive at the conditions which will activate the adhesive composition, but can be made reactive upon application of sufficient energy in the form of radiant energy or in the form of heat at or above the activation temperature, for a time period sufficient to cure the composition. The adhesive composition is flexible, and in the C-stage, is capable of forming an infusible composition which does not melt, flow or decompose when exposed for 10 seconds to molten solder at 260.degree. C. and does not soften when exposed to dichloromethane at 25.degree. C. for one minute. The adhesive composition is suitable for bonding a wire to a surface, to another wire or to itself.