陶瓷顆粒/石墨烯/PDMS複合之熱界面材料開發

Thermal interface materials (TIMs) are widely used for heat dissipation in IC packages and electronic products, which will play an important role in thermal management. The working principle is as follows: there are fine irregular gaps between the surface of the electronic component and the heat sink, the effective contact area ratio is only 10% of the heat sink surface, the rest are air gaps. However, the thermal conductivity of air is only 0.025 W/mK, which is a poor thermal conductor that seriously hinders the heat conduction and results in a poor performance of the heat sink. Using TIMs with high thermal conductivity instead of air gaps can significantly reduce the thermal resistance and make heat sink fully used. In this study, ceramic fillers with high thermal conductivity and polymer colloidal matrix will be pretreated and mixed. In addition, homemade emerging carbon materials with good thermal conductivity, graphene and carbon nanotube, also will be filled. The ceramic particles and graphene complex will create a synergetic effect to achieve the realization of thermal interface materials with high thermal conductivity. The overall execution points of this project include: 1. Ceramic filler treatment with atmospheric plasma: Atmospheric plasma treatment will be used for surface functionalization of alumina (Al2O3) or aluminum nitride (AlN). It will increase the adhesion between the ceramic particles and polydimethylsiloxane (PDMS) by changing the functional groups on the surface of the particles, thus decrease the thermal resistance of the interface. Based on the processing time, the powder blending ratio of different particle size or shape and other parameters, the performance of thermal conductivity will be assessed. 2. Preparation of few-layered graphene: We already have developed a novel and green energy process method, using carbonate as an environmentally friendly graphite intercalation material, combined with thermal shock treatment and ultrasonic agitation to increase the exfoliation effect, and does not require reduction procedure. This process has excellent properties like environmental friendliness, mass production and high quality graphene with good thermal conductivity. 3. Mixed evenly to form TIMs: The vacuum deaeration stirring will be used for uniformly mixing ceramic filler and PDMS. The viscosity is about 25-50 Pa·s (25 °C). Then add appropriate proportions of functionalized multi-wall carbon nanotubes and few-layer graphene. Tubular carbon nanotubes are mixed into the graphene sheets to prevent graphene restacked, thereby increasing the utilization ratio of the graphene surface area, expanding the heat dissipation pathway, forming a heat conductive bridge between the graphene sheets, hence improving the heat conductive performance. 4. Performance evaluation of TIMs: Preliminary qualitative measurements of multiple groups of samples will be carried out using an infrared thermal imager. The samples with good thermal conduction will be outsourced for thermal conductivity measurement based on the ASTM D5470 standard. In this way, the time and costs of R&D can be saved. It is expected that the bottleneck, thermal conductivity less than 10 W/mK, of current insulation typed TIMs (volume resistivity≧10^12 Ω-cm) can be broken through.