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Nanoscale material technology for interconnecting semiconductor devices with high heat dissipation and high temperature capability

Year: 2004
Today, all state-of-the-art semiconductor devices in individual packages or multi-chip power modules are attached to substrates using pastes of lead or lead-free solder alloys or an electrically conductive epoxy. These die-attachments have low electrical and thermal conductivity, and the soldered attachment is susceptible to fatigue failure under cyclic loading. CPES material research has made significant progress in understanding the sintering mechanism of nanoscale particles, and an in-depth knowledge has been gained on the competing physical processes between coagulation and coalescence aggregation of nano-particles. This understanding has enabled us to successfully refine the chemical formulation of nanoscale silver pastes to prevent the coalescence aggregation at low temperatures and to allow the nanoscale powder to consolidate to high densities. Densification of a nanoscale powder is necessary to realize its superior physical and chemical properties, such as high electrical and thermal conductivities, or tailorable dielectric and magnetic properties, needed to enhance the material performance when integrated into a system.

CPES's lead-free nanomaterial attachment possesses better thermal, mechanical, and electrical properties than soldered or epoxied attachment. The low-temperature sintering process is also completely compatible with existing equipment and facilities that use solders or epoxies. Using CPES's material and process, high power-density semiconductor electronic or optoelectronic devices can be operated at high temperatures in excess of 250°C, not attainable with any existing solder-based die-attach and epoxy materials.

The patented technology is expected to achieve 2 times improvement in thermal conductivity, over 6 times improvement in electrical conductivity, and 2.5 times improvement in connection strength.

This technology has inspired the founding of NBE Technologies, LLC, a start-up company established by CPES-VT faculty member, Prof. Guo-Quan Lu. The company recently received financial support from the Running-Start fund managed by the Corporate Research Center (CRC) of Virginia Tech. With this support, NBE is constructing a production facility in the VT KnowledgeWorks building, a business incubation cradle at the CRC. NBE specializes in the manufacturing of nanoscale materials for electronic packaging and biomedical applications. Its nanoscale die-attach materials are being evaluated for possible use by several large manufacturers of power electronics devices and modules.

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