BENCHMARKING ASSEMBLY MATERIALS FOR VERTICALLY ALIGNED CARBON NANOTUBES INTO MICROSYSTEMS

摘要

Carbon nanotubes (CNTs) have attracted much interest in various applications, thanks to their unique thermal, electrical, and mechanical properties [1]. In the field of electronics packaging, vertically aligned CNT (VA-CNT) structures have been utilized as electrical interconnects [2] and thermal interface materials [3] because of the good electrical and thermal conduction in the vertical direction. The most common applied method to fabricate VA-CNT structures is chemical vapor deposition (CVD). During CVD of CNTs, the substrate normally needs to be heated up to a high temperature (~ 600-800 °C), which is unfortunately incompatible with many temperature-sensitive devices and materials in electronics. Different methods were developed to solve this problem. It is possible to lower the growth temperature by for example using plasma-enhanced CVD [4]. However the growth rate and quality are normally significantly deteriorated at lower temperature. It was also demonstrated that CNTs could be grown from locally heated micro-scale heaters [5] but this method adds extra complexity to fabricate and connect the micro heaters. Therefore post-growth techniques have been proposed to transfer CNTs from an original growth substrate to a target substrate at a low temperature. Different assembly materials were used for this purpose, including for example solders [6] and conductive adhesives [7]. In this work we present a benchmarking study of assembly materials for the integration of VA-CNTs, aiming at comparing the electrical and mechanical performance of different assembled CNT structures. Three different materials, including an isotropic conductive adhesive (ICA), an anisotropic conductive adhesives (ACA), and a solder alloy, were used in the assembly of CNTs and compared.