Carbon nanotube thermal pads
Thermal pads, including free-standing examples, are provided for dissipating heat from a heat source like a semiconductor die to a heat management aid such as a heat sink. The thermal pads include a sheet of vertically aligned carbon nanotubes and a surface layer. One such surface layer has a thickness of less than 500 microns. Another includes a metal layer having a thickness of less than 500 microns and an intermediate layer attaching the metal layer to the sheet of carbon nanotubes.
1 . A free-standing thermal pad comprising:
a sheet of carbon nanotubes having first and second opposing sides, the carbon nanotubes being generally aligned perpendicular to the sheet; and
a first surface layer disposed on the first side of the sheet of carbon nanotubes and including
a first metal layer having a thickness of less than 500 microns, and
an intermediate layer attaching the first metal layer to the first side of the sheet.
2 . The free-standing thermal pad of claim 1 wherein the first metal layer includes copper.
3 . The free-standing thermal pad of claim 2 further comprising a second surface layer disposed on the second side of the sheet of carbon nanotubes and including silicon.
4 . The free-standing thermal pad of claim 1 further comprising a matrix material filling an interstitial space between the carbon nanotubes between the first and second sides of the sheet.
5 . The free-standing thermal pad of claim 4 wherein the matrix material includes parylene.
6 . The free-standing thermal pad of claim 1 further comprising a base metal layer around the carbon nanotubes at the first side of the sheet, wherein an interstitial space of the sheet between the base metal layer and the second side of the sheet is unfilled.
7 . The free-standing thermal pad of claim 1 wherein an interstitial space of the sheet between the first and second sides of the array is unfilled.
8 . The free-standing thermal pad of claim 1 further comprising a second surface layer disposed on the second side of the sheet of carbon nanotubes.
9 . The free-standing thermal pad of claim 8 wherein the second surface layer includes a second metal layer.
10 . The free-standing thermal pad of claim 9 wherein the ends of the carbon nanotubes of the second side of the sheet extend partially into the second metal layer.
11 . The free-standing thermal pad of claim 9 wherein the second surface layer further includes a third metal layer, wherein the second metal layer is between the second side of the sheet of carbon nanotubes and the third metal layer, and wherein the second metal layer is characterized by a melting point less than a melting point of the third metal layer.
12 . A free-standing thermal pad comprising:
an array of carbon nanotubes having first and second opposing sides, the carbon nanotubes being generally aligned perpendicular to the sides of the array and disposed in discrete bundles, the bundles being separated by unfilled interstitial space; and
a first surface layer disposed on the first side of the array of carbon nanotubes and having a thickness of less than 500 microns.
13 . The free-standing thermal pad of claim 12 further comprising a base metal layer around the carbon nanotubes at the first side of the array, wherein the interstitial space between the bundles is unfilled between the base metal layer and the second side of the array.
14 . The free-standing thermal pad of claim 12 further comprising a second surface layer disposed on the second side of the array of carbon nanotubes.
15 . A thermal pad comprising:
a substrate having first and second planar surfaces;
a first array of carbon nanotubes disposed on the first planar surface, the carbon nanotubes being generally aligned perpendicular to the first surface; and
a second array of carbon nanotubes disposed on the second planar surface, the carbon nanotubes being generally aligned perpendicular to the second surface.
16 . The thermal pad of claim 15 wherein the substrate comprises a metal foil.
17 . The thermal pad of claim 15 wherein a thickness of the substrate is less than 500 microns.
18 . A free-standing thermal pad consisting of:
a sheet of carbon nanotubes generally aligned perpendicular to the sheet; and
a metal layer disposed over one side of the sheet, the ends of the carbon nanotubes extending partially into the metal layer.
19 . The free-standing thermal pad of claim 18 wherein the metal layer comprises copper.
20 . The free-standing thermal pad of claim 18 therein the metal layer includes a planar surface.