A carbon-based material developed at the University of Leeds could provide a solution to the growing problems of thermal management encountered in the electrical and electronic industries.
The use of ever-higher power density demands improvements to thermal management. Poor thermal management can cause processors to overheat, leading to reduced lifetime and unreliability.
The patented material exploits the high in-plane thermal conductivity of graphite and is composed of highly oriented mesophase-based graphite (HOMG) which is spun into tape and can be compressed into bulk material.
HOMG tape’s highly ordered graphitic structure makes it ideal for conducting heat along its length. The inventors in the University’s Department of Materials have shown that the specific thermal conductivity along its axis is at least ten times that of copper.
Bulk material is made by compacting the tapes prior to carbonisation. This produces a strongly bonded, almost pore-free monolithic graphitic body that can be easily machined.
The tape is first formed by spinning organic liquid crystalline pitch-based materials, followed by ‘stabilisation’ and heat treatment at temperatures up to 3000C. The highly ordered structure in the tape is created by carefully controlling the orientation of the liquid crystalline molecules during melt spinning.
After heat treatment at 1000C, the carbon tape is highly flexible and can easily be coiled with a radius of less than 20mm. It has a tensile strength of 1 Gpa and a Young modulus of 150 Gpa.
After graphitisation at 2700C, HOMG tapes exhibit rugged fracture surfaces indicating significant fracture toughness with a tensile strength of about 2Gpa. This underlines the possibility of HOMG tapes being used as structural materials.
Dr. Dick Gale
University of Leeds