Patent ID: 6894400

Claim:
A packaged electronic device comprising 1) a die having a dimension of 15 mm or greater and including an array of connections, 2) a substrate including a mating array physically and electrically interconnected with said array of the die and external electrical connections, and 3) an underfill material between said die and said substrate in the region of said arrays wherein said underfill material has A) an elastic modulus at temperatures above the glass transition temperature, T g , of said underfill material between about 100 and 300 MPa, B) a T g between about 55° C. to 110° C., and C) an elastic modulus at temperatures below the T g of said underfill material between about 2 GPa and 10 GPa where said array of said substrate has a stiffness less than 38 GPa and about 3 GPa to 15 GPa where said array of said substrate has a stiffness of 38 GPa and greater, and wherein said underfill material includes filler particles with average diameter of 15 μm or less.