Bulk high thermal conductivity feedstock and method of making thereof
View Patent ↗The invention relates to a feedstock material for use in making heat spreaders, comprising a sheet of annealed pyrolytic graphite having a thermal conductivity of greater than 1000 watts/m-K, a size in any dimension of at least 5 cm and a thickness of at least 0.2 mm. In one embodiment, the feedstock is made by hot-pressing a stack of alternate layers of pyrolytic graphite sheets with flat graphite dies for a finished sheet of annealed pyrolytic graphite comprising a plurality of layers being parallel to each other of at least 0.075 degrees per mm of thickness. In another embodiment, the finished sheet of annealed pyrolytic graphite is made by graphitizing a stack of films comprising a high-carbon polymer.
1. An annealed thermal pyrolytic graphite (“TPG”) feedstock material comprising
a board of annealed pyrolytic graphite having a thermal conductivity of greater than 1000 watts/m-K, a size in any dimension of at least 5 cm, a thickness of at least 0.2 mm, wherein
said board consists essentially of a plurality of flat graphite layers being parallel to each other;
said board has a flatness with a deviation angle of less than 0.075 degrees per mm of thickness; and
said annealing is at a temperature of above 2900° C.
2. The annealed TPG material of claim 1 , having length and width dimensions of at least 5 cm respectively.
3. The annealed TPG material of claim 1 , having a thickness of at least 0.5 mm.
4. The annealed TPG material of claim 1 , in the form of a graphitized board of polyimide.
5. The annealed TPG material of claim 4 , wherein said graphitized board of polyiniide comprises a plurality of polyirnide films having a thickness of less than 50 microns graphitized at a temperature of at least about 2800° C.
6. The annealed TPG material of claim 1 , in the form of a hot pressed board of pyrolytic graphite.
7. The annealed TPG material of claim 6 , wherein said board of pyrolytic graphite is hot-pressed by heating a stack of alternate layers of graphite plates and pyrolytic graphite layers at sufficient temperature and pressure for a sufficient period of time to convert said pyrolytic graphite into highly oriented pyrolytic graphite.
8. The annealed TPG material of claim 7 , wherein said board of pyrolytic graphite is hot-pressed by using a plurality of graphite plates as dies.
9. An article comprising the annealed TPG feedstock material of claim 1 .