Abstract: An electronic structure includes an electronic device coupled to a substrate by conductive bumps and ball limiting metallurgy (BLM). Underfill material having filler particles is disposed in a space between the electronic device and the substrate. A weight percentage of the filler particles is at least about 60%. A particle size of at least 90 wt % of the filler particles is less than about 2 ?m and/or the filler particles are coated by an organic coupling agent. Once the underfill material is fully cured, its coefficient of thermal expansion is no more than 30 PPM/° C., and its glass transition temperature is at least 100° C., and its adhesion to a passivation layer of the electronic device, to the substrate and to the electronic device at its edges is such that the electronic structure passes standardized reliability tests without delamination of the ball limiting metallurgy.

Abstract: An electronic structure includes an electronic device coupled to a substrate by conductive bumps and ball limiting metallurgy (BLM). Underfill material having filler particles is disposed in a space between the electronic device and the substrate. A weight percentage of the filler particles is at least about 60%. A particle size of at least 90 wt % of the filler particles is less than about 2 ?m and/or the filler particles are coated by an organic coupling agent. Once the underfill material is fully cured, its coefficient of thermal expansion is no more than 30 PPM/° C., and its glass transition temperature is at least 100° C., and its adhesion to a passivation layer of the electronic device, to the substrate and to the electronic device at its edges is such that the electronic structure passes standardized reliability tests without delamination of the ball limiting metallurgy.