Methods for forming carbon nanotube thermal pads

Abstract

Methods for forming thermal pads including arrays of vertically aligned carbon nanotubes are provided. The thermal pads are formed on various substrates, including foils, thin self-supporting polished metals, semiconductor dies, heat management aids, and lead frames. The arrays are growth from a catalyst layer disposed on the substrate. Forming the array can include leaving the ends of the nanotubes unfinished, attaching a foil thereto, or coating the ends with a metal layer. The metal layer coating can then be polished to a desired smoothness. The array can be filled with a matrix material, only partially filled, or left unfilled. Where the substrate is a foil, the method can be a continuous process where foil is taken from a roll and fed through a series of formation steps. Where the substrate is a lead frame, heating can be generated by applying an current to a pad of the lead frame.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates generally to the field of semiconductor packaging and more particularly to methods for forming structures that employ carbon nanotubes for thermal dissipation. [0003] 2. Description of the Prior Art [0004] A carbon nanotube is a molecule composed of carbon atoms arranged in the shape of a cylinder. Carbon nanotubes are very narrow, on the order of nanometers in diameter, but can be produced with lengths on the order of hundreds of microns. The unique structural, mechanical, and electrical properties of carbon nanotubes make them potentially useful in electrical, mechanical, and electromechanical devices. In particular, carbon nanotubes possess both high electrical and thermal conductivities in the direction of the longitudinal axis of the cylinder. For example, thermal conductivities of individual carbon nanotubes of 3000 W / m-°K and higher at room temperature have been reported. [0005] ...

AI Technical Summary

Benefits of technology

[0008] The substrate is preferably thin and in some embodiments is a copper foil or a thinned silicon wafer. The thickness of the substrate can be less than 500μ, less than 250μ, or less than 100μ. In some embodiments, an interface layer is formed on the substrate before the catalyst layer is formed. In some of these embodiments a barrier layer is formed on the substrate before the interface layer is formed. The catalyst layer can be patterned so that the array forms bundles of aligned carbon nanotubes on the patterned catalyst layer. Spacers can also be provided on the planar surface before forming the array so that the finished thermal pad will include spacers that can serve to protect the carbon nanotubes of the array from damage during handling and assembly.

Problems solved by technology

For example, in the semiconductor industry, devices that consume large amounts of power typically produce large amounts of heat.

However, thermal greases are both messy and require additional packaging, such as spring clips or mounting hardware, to keep the assembly together, and thermal greases have relatively low thermal conductivities.

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