Functional Materials for Thermal Management Applications
Abstract
The inefficient dissipation of heat is a crucial problem that limits the reliability and
performance of all electronic systems. As electronic devices get smaller and more
powerful, and moving components of machinery operate at higher speeds, the need for
better thermal management strategies is becoming increasingly important. Heat removal
during the operation of electronic, electrochemical, and mechanical devices is facilitated
by high-performance thermal interface materials (TIMs), which are utilized to couple
devices to heat sinks. Herein, we report a new class of TIMs involving the chemical
integration of boron nitride nanosheets (BNNS), soft organic linkers, and a metal matrix -
which are prepared by chemisorption coupled electrodeposition approach. Thermal and
mechanical characterization of the copper-based hybrid nanocomposites involving
thiosemicarbazide demonstrates bulk thermal conductivities ranging from 211 to 277
W/(m.K), which are very high considering their relatively low elastic modulus values on
the order of 15 to 30 GPa. The synergistic combination of these properties leads to the
lowest measured total thermal resistivity to date for a TIM with a typical bondline
thickness of 30-50 μm: 0.38 to 0.56 mm^2.K/W. Moreover, its coefficient of thermal
expansion (CTE) is 11 ppm/K, forming a mediation zone with a low thermally-induced
axial stress due to its close proximity to the CTE of most coupling surfaces needing
thermal management. Furthermore, preliminary electrochemical tests revealed that the
presence of organic ligands and BNNS in the hybrid nanocomposite TIMs improves the
corrosion protection behavior of the TIMs by nearly 72%.
Further analysis of the hybrid nanocomposite TIMs included the replacement of
thiosemicarbazide with various organic ligands and the replacement of copper matrix with
silver. Compared to all the ligands that were used in copper-based hybrid nanocomposites,
the most promising thermal and mechanical test results were obtained from
thiosemicarbazide. On the other hand, the best silver-based nanocomposite TIM was
determined to be the one involving the ligand 2-mercapto-5-benzimidazolecarboxylic
acid, in which the thermal conductivity was near 360 W/m.K, and elastic modulus and
hardness were about 35 GPa and 0.25 GPa, respectively. The promising results indicate
that metal-inorganic-organic nanocomposite TIMs can be great alternatives to currently
used TIMs in the market.
Additionally, polystannane nanocomposite involving graphene nano particles as
fillers were synthesized, which showed thermal conductivities up to 40 W/m.K at 10 wt%
loading. Also, these composites were found to have higher stability in ambient conditions
towards humidity and light where the degradation kinetics of first order showed 10-fold
decrease in rate constant. These improvements in thermal properties and stability can
allow the polymeric metals in application towards thermal management.
Subject
Thermal interface materialsBoron nitride
Functionalization
Electrodeposition
Nanocomposites
Graphene
Polystannane
Citation
Nagabandi, Nirup (2017). Functional Materials for Thermal Management Applications. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /187288.