2007 R&D 100 Winner

Companies looking for chip-interconnect solutions for high-volume electronic products can choose from two major types: solder alloys and conductive epoxies. For high-temperature applications, however, researchers at Virginia Tech and NBE Technologies LLC, both of Blacksburg, believe neither choice is optimal. Steering away from gold, tin, or lead mixtures, these researchers developed nanoTach, a smooth viscous semiconductive nanomaterial paste designed to significantly improve performance and reliability above 175°C.

The nanoTach paste starts as a dispersion of surfactant, organic thinner, and silver nanopowder. Under ambient pressure, various organics are evaporated and burned, removing molecules that separate the silver nanoparticles from each other. A strong thermodynamic driving force, proportional to the inverse of particle size, begins the sintering process, and the objective surfaces are bound to the paste via atomic diffusion at about 265°C.

nanoTach is expected to find use in wide bandgap semiconductor devices made of silicon carbide and gallium nitride. In addition to the conductivity properties of silver, the paste’s low elastic modulus will relieve thermomechanical stresses, lengthening operating lifetime.

Smooth viscous semiconductive nanomaterial paste

Virginia Tech
NBE Technologies LLC

Originally published in R&D Magazine, September, 2007