ABSTRACT
With the ultra-fast development of personal portable electronic devices, it is important to explore new die attach film (DAF) materials in the limited mounting area and height in order to meet the requirements of a high packaging density and a high operating speed. Graphene-based epoxy nanocomposites are becoming one of the most promising candidates for the next generation of DAFs combining the ultra-high thermal conductivity of graphene, and ultra-strong adhesion of epoxy polymers. However, poor dispersion and weak interfacial connections, due to the overly smooth surface of graphene nanosheets, are still pressing issues that limit their industrial applications. Additionally, pristine graphene nanosheets have only a small effect on improving the glass transition temperature (Tg) of epoxy composites to meet the requirements of DAFs. In this work, melamine-functionalized graphene is synthesized by using a nondestructive ball milling process, which results in greater dispersion and enhancement of the interfacial connections between graphene and epoxy resins demonstrated by both experimental and simulation results. In particular, the aromatic triazine rings of melamine increase Tg in the cured resin, thus improving the thermal stability of DAFs. The melamine-graphene (M-G) epoxy nanocomposites synthesized have a high Tg of 172 °C and an out-of-plane thermal conductivity of 1.08 W m-1 K-1 at 10 wt% loading. This is 6.4 multiples higher than that of neat epoxy. Moreover, M-G epoxy nanocomposites exhibit superb thermal stability, an effective low coefficient of thermal expansion (CTE), low moisture adsorption, and a useful high electrical resistivity. In the DAF performance test, involving experimentation and modeling, the samples present a better cooling capability and heat dissipation. This supports the idea that our findings have potential to be applied in the next generation of DAFs for high-power and high-density 3D packaging.
ABSTRACT
Thermal insulation materials are highly sought after for applications such as building envelopes, refrigerators, cryogenic fuel storage chambers, and water supply piping. However, current insulation materials either do not provide sufficient insulation or are costly. A new class of insulation materials, hollow silica particles, has attracted tremendous attention due to its potential to provide a very high degree of thermal insulation. However, current synthesis strategies provide hollow silica particles at very low yields and at high cost, thus, making the particles unsuitable for real-world applications. In the present work, a synthesis process that produces hollow silica particles at very high yields and at a lower cost is presented. The effect of an infrared heat absorber, carbon black, on the thermal conductivity of hollow silica particles is also investigated and it is inferred that a carbon black-hollow silica particle mixture can be a better insulating material than hollow silica particles alone.
ABSTRACT
The purification of conductive polymer (e.g., polyaniline) particles is a challenging task, especially when the particle size is small. Herein, we demonstrate a unique strategy (electrode-based) to purify polyaniline particles by exploiting the difference in surface charge between particles and surfactants, and compare the results with a commonly used purification strategy (washing).
