On Thermal Interface Materials With Polydisperse Fillers: Packing Algorithm and Effective Properties

2018 ◽  
Author(s):  
Piyas Chowdhury ◽  
Kamal Sikka ◽  
Anuja De Silva ◽  
Indira Seshadri
Keyword(s):  
Thermal Conductivity ◽  
Elastic Modulus ◽  
Volume Fraction ◽  
Effective Properties ◽  
Material Design ◽  
High Volume ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Packing Algorithm ◽  
Interface Materials

Thermal interface materials (TIMs), which transmit heat from semiconductor chips, are indispensable in today’s microelectronic devices. Designing superior TIMs for increasingly demanding integration requirements, especially for server-level hardware with high power density chips, remains a particularly coveted yet challenging objective. This is because achieving desired degrees of thermal-mechanical attributes (e.g. high thermal conductivity, low elastic modulus, low viscosity) poses contradictory challenges. For instance, embedding thermally conductive fillers (e.g. metallic particles) into a compliant yet considerably less conductive matrix (e.g. polymer) enhances heat transmission, however at the expense of overall compliance. This leads to extensive trial-and-error based empirical approaches for optimal material design. Specifically, high volume fraction filler loading, role of filler size distribution, mixing of various filler types are some outstanding issues that need further clarification. To that end, we first forward a generic packing algorithm with ability to simulate a variety of filler types and distributions. Secondly, by modeling the physics of heat/force flux, we predict effective thermal conductivity, elastic modulus and viscosity for various packing cases.

Rheological Study of Micro Particle Laden Polymeric Thermal Interface Materials: Part 1 — Experimental

2002 ◽  
Author(s):  
Ravi S. Prasher ◽  
Jim Shipley ◽  
Suzana Prstic ◽  
Paul Koning ◽  
Jin-Lin Wang
Keyword(s):  
Thermal Conductivity ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Electronics Cooling ◽  
Bond Line ◽  
Rheological Parameters ◽  
Thermal Interface Materials ◽  
Particle Volume ◽  
Thermal Interface ◽  
Interface Materials

Particle laden polymers are one of the most prominent thermal interface materials (TIM) used in electronics cooling. Most of the research groups have primarily dealt with the understanding of the thermal conductivity of these types of TIMs. Thermal resistance is not only dependent on the thermal conductivity but also on the bond line thickness (BLT) of these TIMs. It is not clear that which material property(s) of these particle laden TIMs affects the BLT. This paper discusses the experimental measurement of rheological parameters such as non-Newtonian strain rate dependent viscosity and yield stress for 3 different particle volume fraction and 3 different base polymer viscosity materials. These rheological and BLT measurements vs. pressure will be used to model the BLT of particle-laden systems for factors such as volume fraction.

Thermal Transport in Self-Assembled Conductive Networks for Thermal Interface Materials

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Lin Hu ◽  
William Evans ◽  
Pawel Keblinski
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Volume Fraction ◽  
Liquid Solution ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Rapid Formation ◽  
Dynamics Simulations ◽  
Solid Liquid ◽  
Interface Materials

We present a concept for development of high thermal conductivity thermal interface materials (TIMs) via a rapid formation of conductive network. In particular we use molecular dynamics simulations to demonstrate the possibility of a formation of a network of solid nanoparticles in liquid solution and establish wetting and volume fraction conditions required for a rapid formation of such network. Then, we use Monte-Carlo simulations to determine effective thermal conductivity of the solid/liquid composite material. The presence of a percolating network dramatically increases the effective thermal conductivity, as compared to values characterizing dispersed particle structures.

Bond Line Thickness of Thermal Interface Materials With Carbon Nanotubes

2005 ◽  
Author(s):  
Senthil A. G. Singaravelu ◽  
Xuejiao Hu ◽  
Kenneth E. Goodson
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Volume Fraction ◽  
Bond Line ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Line Thickness ◽  
Bond Line Thickness ◽  
The Impact ◽  
Interface Materials

Increasing power dissipation in today’s microprocessors demands thermal interface materials (TIMs) with lower thermal resistances. The TIM thermal resistance depends on the TIM thermal conductivity and the bond line thickness (BLT). Carbon Nanotubes (CNTs) have been proposed to improve the TIM thermal conductivity. However, the rheological properties of TIMs with CNT inclusions are not well understood. In this paper, the transient behavior of the BLT of the TIMs with CNT inclusions has been measured under controlled attachment pressures. The experimental results show that the impact of CNT inclusions on the BLT at low volume fractions (up to 2 vol%) is small; however, higher volume fraction of CNT inclusions (5 vol%) can cause huge increase in TIM thickness. Although thermal conductivities are higher for higher CNT fractions, a minimum TIM resistance exists at some optimum CNT fraction for a given attachment pressure.

Rheological Study of Micro Particle Laden Polymeric Thermal Interface Materials: Part 2 — Modeling

2002 ◽  
Author(s):  
Ravi S. Prasher ◽  
Jim Shipley ◽  
Suzana Prstic ◽  
Paul Koning ◽  
Jin-Lin Wang
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Yield Stress ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Thermal Interface Materials ◽  
Particle Volume ◽  
Thermal Interface ◽  
Complete Set ◽  
Interface Materials

Currently there are no models to predict the thickness or the bondline thickness (BLT) of particle laden polymeric thermal interface materials (TIM) for parameters such as particle volume fraction and pressure. TIMs are used to reduce the thermal resistance. Typically this is achieved by increasing the thermal conductivity of these TIMs by increasing the particle volume fraction, however increasing the particle volume fraction also increases the BLT. Therefore, increasing the particle volume fraction may lead to an increase in the thermal resistance after certain volume fraction. This paper introduces a model for the prediction of the BLT of these particle laden TIMs. Currently thermal conductivity is the only metric for differentiating one TIM formulation from another. The model developed in this paper introduces another metric: the yield stress of these TIMs. Thermal conductivity and the yield stress together constitute the complete set of material parameters needed to define the thermal performance of particle laden TIMs.

Thermal Resistance of Particle Laden Polymeric Thermal Interface Materials

2003 ◽  
Author(s):  
Ravi S. Prasher ◽  
Jim Shipley ◽  
Suzana Prstic ◽  
Paul Koning ◽  
Jin-Lin Wang
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Volume Fraction ◽  
Applied Pressure ◽  
Electronics Cooling ◽  
Thermal Design ◽  
Thermal Interface Materials ◽  
Particle Volume ◽  
Thermal Interface ◽  
Interface Materials

Particle laden polymers are one of the most prominent thermal interface materials (TIM) used in electronics cooling. Most of the research has primarily dealt with the understanding of the thermal conductivity of these types of TIMs. For thermal design, reduction of the thermal resistance is the end goal. Thermal resistance is not only dependent on the thermal conductivity, but also on the bond line thickness (BLT) of these TIMs. It is not clear which material property(s) of these particle laden TIMs affects the BLT and eventually the thermal resistance. This paper introduces a rheology based semi-empirical model for the prediction of the BLT of these TIMs. BLT depends on the yield stress of the particle laden polymer and the applied pressure. The BLT model combined with the thermal conductivity model can be used for modeling the thermal resistance of these TIMs for factors such as particle volume faction, particle shape, base polymer viscosity, etc. This paper shows that there exists an optimal filler volume fraction at which thermal resistance is minimum. Finally this paper develops design rules for the optimization of thermal resistance for particle laden TIMs.

Predicting Thermal Characteristics of Particle Laden Thermal Interface Materials

2009 ◽  
Author(s):  
Reza H. Khiabani ◽  
Yogendra Joshi ◽  
Cyrus Aidun
Keyword(s):  
Thermal Conductivity ◽  
Thermal Performance ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Thermal Characteristics ◽  
Thermal Conductivity Ratio ◽  
Thermal Interface Materials ◽  
Particle Volume ◽  
Thermal Interface ◽  
Interface Materials

Particle laden Thermal Interface Materials (TIMs) are used extensively in thermal packaging of electronic components to enhance the heat transfer between heat dissipating components and the thermal management layers. In this paper, the thermal performance of particle laden TIMs is studied numerically, using the Lattice Boltzmann method. The effect of particle volume fraction, particle size and the thermal conductivity ratio on the thermal performance of particle laden TIMs are examined. The results for the effective thermal conductivity of particle laden greases are in agreement with the existing analytical and experimental results reported in the literature.

Hierarchical Modeling and Trade-Off Studies in Design of Thermal Interface Materials

2005 ◽  
Author(s):  
X. Zhang ◽  
S. Kanuparthi ◽  
G. Subbarayan ◽  
B. Sammakia ◽  
S. Tonapi
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Thermal Interface Materials ◽  
Particle Volume ◽  
Heat Spreader ◽  
Thermal Interface ◽  
Volume Fractions ◽  
Interface Materials

Particle laden polymer composites are widely used as thermal interface materials in the electronics cooling industry. The projected small chip-sizes and high power applications in the near future demand higher values of effective thermal conductivity of the thermal interface materials (TIMs) used between the chip and the heat-spreader and the heat-spreader and heat-sink. However, over two decades of research has not yielded materials with significantly improved effective thermal conductivities. A critical need in developing these TIMs is apriori modeling using fundamental physical principles to predict the effect of particle volume fraction and arrangements on effective behavior. Such a model will enable one to optimize the structure and arrangement of the material. The existing analytical descriptions of thermal transport in particulate systems under predict (as compared to the experimentally observed values) the effective thermal conductivity since these models do not accurately account for the effect of inter-particle interactions, especially when particle volume fractions approach the percolation limits of approximately 60%. Most existing theories are observed to be accurate when filler material volume fractions are less than 30–35%. In this paper, we present a hierarchical, meshless, computational procedure for creating complex microstructures, explicitly analyzing their effective thermal behavior, and mathematically optimizing particle sizes and arrangements. A newly developed object-oriented symbolic, java language framework termed jNURBS implementing the developed procedure is used to generate and analyze representative random microstructures of the TIMs.

Thermal Resistance of Particle Laden Polymeric Thermal Interface Materials

2003 ◽  
Vol 125 (6) ◽  
pp. 1170-1177 ◽  
Author(s):  
Ravi S. Prasher ◽  
Jim Shipley ◽  
Suzana Prstic ◽  
Paul Koning ◽  
Jin-lin Wang
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Volume Fraction ◽  
Applied Pressure ◽  
Electronics Cooling ◽  
Thermal Design ◽  
Thermal Interface Materials ◽  
Semiempirical Model ◽  
Thermal Interface ◽  
Interface Materials

Particle laden polymers are one of the most prominent thermal interface materials (TIM) used in electronics cooling. Most of the research has primarily dealt with the understanding of the thermal conductivity of these types of TIMs. For thermal design, reduction of the thermal resistance is the end goal. Thermal resistance is not only dependent on the thermal conductivity, but also on the bond line thickness (BLT) of these TIMs. It is not clear which material property(s) of these particle laden TIMs affects the BLT and eventually the thermal resistance. This paper introduces a rheology based semiempirical model for the prediction of the BLT of these TIMs. BLT depends on the yield stress of the particle laden polymer and the applied pressure. The BLT model combined with the thermal conductivity model can be used for modeling the thermal resistance of these TIMs for factors such as particle volume faction, particle shape, base polymer viscosity, etc. This paper shows that there exists an optimal filler volume fraction at which thermal resistance is minimum. Finally this paper develops design rules for the optimization of thermal resistance for particle laden TIMs.

Hybrid Nanocomposite Thermal Interface Materials: The Thermal Conductivity and the Packing Density

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Tingting Zhang ◽  
Bahgat G. Sammakia ◽  
Zhihao Yang ◽  
Howard Wang
Keyword(s):  
Thermal Conductivity ◽  
Packing Density ◽  
Volume Fraction ◽  
Thermal Interface Material ◽  
Thermal Interface Materials ◽  
Hybrid Nanocomposite ◽  
Thermal Interface ◽  
Mechanical Performances ◽  
Interface Materials ◽  
Network Form

We have investigated a novel hybrid nanocomposite thermal interface material (TIM) that consists of silver nanoparticles (AgNPs), silver nanoflakes (AgNFs), and copper microparticles (CuMPs). Continuous metallic network form while AgNPs and AgNFs fuse to join bigger CuMPs upon hot compression, resulting in superior thermal and mechanical performances. The assembly temperature is as low as 125 °C due to the size effect of silver nanoparticulates. The thermal conductivity, k, of the hybrid nanocomposite TIMs is found to be in the range of 15–140 W/mK, exceeding best-performing commercial thermal greases, while comparable to high-end solder TIMs. The dependence of k on the solid packing density and the volume fraction of voids is discussed through comparing to model predictions.

Characterizing Bulk Thermal Conductivity and Interface Contact Resistance Effects of Thermal Interface Materials in Electronic Cooling Applications

2003 ◽  
Author(s):  
Vadim Gektin ◽  
Sai Ankireddi ◽  
Jim Jones ◽  
Stan Pecavar ◽  
Paul Hundt
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Contact Resistance ◽  
Thermal Performance ◽  
Electronic Cooling ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Interface Contact ◽  
Interface Materials ◽  
Bulk Thermal Conductivity

Thermal Interface Materials (TIMs) are used as thermally conducting media to carry away the heat dissipated by an energy source (e.g. active circuitry on a silicon die). Thermal properties of these interface materials, specified on vendor datasheets, are obtained under conditions that rarely, if at all, represent real life environment. As such, they do not accurately portray the material thermal performance during a field operation. Furthermore, a thermal engineer has no a priori knowledge of how large, in addition to the bulk thermal resistance, the interface contact resistances are, and, hence, how much each influences the cooling strategy. In view of these issues, there exists a need for these materials/interfaces to be characterized experimentally through a series of controlled tests before starting on a thermal design. In this study we present one such characterization for a candidate thermal interface material used in an electronic cooling application. In a controlled test environment, package junction-to-case, Rjc, resistance measurements were obtained for various bondline thicknesses (BLTs) of an interface material over a range of die sizes. These measurements were then curve-fitted to obtain numerical models for the measured thermal resistance for a given die size. Based on the BLT and the associated thermal resistance, the bulk thermal conductivity of the TIM and the interface contact resistance were determined, using the approach described in the paper. The results of this study permit sensitivity analyses of BLT and its effect on thermal performance for future applications, and provide the ability to extrapolate the results obtained for the given die size to a different die size. The suggested methodology presents a readily adaptable approach for the characterization of TIMs and interface/contact resistances in the industry.

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