Advancement in High Thermal Conductive Graphite for Microelectronic Packaging

Abstract

Thermal management is an increasingly critical problem in today’s microelectronics industry. As power increases and size decreases, innovative materials with high thermal conductivity (TC), lightweight, and many times low coefficient of thermal expansion (CTE) are desired to solve these thermal challenges. Thermal Pyrolytic Graphite (TPG*), a unique synthetic material produced via chemical vapor deposition, consists of layers of highly oriented stacked graphene planes and exhibits excellent in-plane thermal conductivity (>1500 W/mK) and very low density (2.25 g/cm³). In order to take advantage of its superior properties for thermal management, various forms of TPG-metal composite products were developed since 1990s. TPG composite with metal encapsulation simultaneously achieves high thermal conductivity from the TPG core and mechanical integrity from the metal shell. Multiple proprietary bonding technologies enable an intimate and strong joint between TPG and dissimilar metals, including Al, Cu, Sn, WCu, MoCu, AlSiC, and AlBe. In addition, the variety of compatible metals adds new functionalities to the composite, such as platability and solderability for direct die attachment, CTE matching to semiconductor, and flexibility for off-plane connectivity. The design guidance, property, and reliability of the TPG-metal composites are reviewed in detail. Tailored TPG-metal composites, i.e., TC1050* heat spreader for board level, TMP-EX heat sink for chip level, and TMP-FX thermal strap for tight space, were developed to tackle specific thermal management challenges. Individually, their performance and application examples are discussed. Great benefits from the integrated TPG solutions are anticipated to a broad range of high power electronics applications, including RF/MW, laser, LED, power management, etc.