CTE-Tailorable Copper Heat Spreaders, Heat Sinks, and Heat Pipes via a nanoCopper Approach

Abstract

Since the last ever ITRS report, published in 2015, acknowledged the end of profitable scaling (Moore's law) the industry's focus has shifted to packaging as the focus area to drive down cost, size and increase performance [1]. Heterogeneous integration was recognized as being the key vehicle to continue miniaturization. However, it requires the combination and close packing of vastly different materials like low CTE semiconductors (Si, SiC, GaN, etc.) with high CTE heat dissipation materials (Cu/Al) to prevent overheating. The very different mechanical properties have led to warpage, delamination and early failures and have become the limiting factors in yield and reliability. Therefore, heat dissipation and CTE have become the roadblocks to technological advancement in packaging: we need new materials with matching properties not currently available. Solutions were attempted in the past with WCu and AlSiC macro-composites with limited success. Issues like high density, limited CTE tailoring, challenging high temperature manufacture and lack of solderability prevented their widespread use. In an effort to solve this problem, we used nanotechnology to design materials with new properties that are not available in nature. We used our copper-based nanomaterial to create a materials system that allows precise CTE-tuning between 3–17 ppm while retaining the highest possible thermal conductivity. The ready flowability of the formulated paste precursor drastically improves processability at low temperatures (200–240 °C) in minutes allowing the use of a rapid injection molding process, enabling low-cost mass-production of near-net-shape parts. Importantly, it can be soldered to directly without additional metallization. This ActiveCopper (aCu) materials system can replace the copper coin technology and readily manufacture CTE-matched lead-frames, heat sinks/spreaders and heat pipes for maximum heat dissipation.