Effects of surface roughness, temperature and pressure on interface thermal resistance of thermal interface materials

2019 ◽  
Vol 140 ◽  
pp. 705-716 ◽  
Author(s):  
Jian-Wei Zhao ◽  
Rui Zhao ◽  
Yan-Kai Huo ◽  
Wen-Long Cheng
Keyword(s):  
Surface Roughness ◽  
Thermal Resistance ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Interface Thermal Resistance ◽  
Temperature And Pressure ◽  
Interface Materials

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.

Development of a Compliant Nanothermal Interface Material

2011 ◽  
Author(s):  
David Shaddock ◽  
Stanton Weaver ◽  
Ioannis Chasiotis ◽  
Binoy Shah ◽  
Dalong Zhong
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Thermal Stresses ◽  
Performance Testing ◽  
High Thermal Conductivity ◽  
Thermal Interface Material ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Bondline Thickness ◽  
Interface Materials

The power density requirements continue to increase and the ability of thermal interface materials has not kept pace. Increasing effective thermal conductivity and reducing bondline thickness reduce thermal resistance. High thermal conductivity materials, such as solders, have been used as thermal interface materials. However, there is a limit to minimum bondline thickness in reducing resistance due to increased fatigue stress. A compliant thermal interface material is proposed that allows for thin solder bondlines using a compliant structure within the bondline to achieve thermal resistance <0.01 cm2C/W. The structure uses an array of nanosprings sandwiched between two plates of materials to match thermal expansion of their respective interface materials (ex. silicon and copper). Thin solder bondlines between these mating surfaces and high thermal conductivity of the nanospring layer results in thermal resistance of 0.01 cm2C/W. The compliance of the nanospring layer is two orders of magnitude more compliant than the solder layers so thermal stresses are carried by the nanosprings rather than the solder layers. The fabrication process and performance testing performed on the material is presented.

Advanced Thermal Interface Materials

2006 ◽  
Vol 968 ◽  
Author(s):  
Yimin Zhang ◽  
Allison Xiao ◽  
Jeff McVey
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Thermal Energy ◽  
Heat Sink ◽  
Electronic Device ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Current State ◽  
Interface Materials ◽  
State Of Art

ABSTRACTThermal interface materials (TIMs) are used to dissipate thermal energy from a heat-generating device to a heat sink via conduction. The growing power density of the electronic device demands next-generation high thermal conductivity and/or low thermal resistance TIMs. This paper discusses the current state-of-art TIM solutions, particularly fusible particles for improved thermal conductivity. The paper will address the benefits and limitations of this approach, and describe a system with unique filler morphology. Thermal resistance and diffusivity/conductivity characterization techniques are also discussed.

Thermal Resistance of Bond-Lines Formed With Composite Thermal Interface Materials

2005 ◽  
Author(s):  
Gary Lehmann ◽  
Hao Zhang ◽  
Arun Gowda ◽  
David Esler
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Thermal Resistance ◽  
Bond Line ◽  
Surface Conductance ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Bond Line Thickness ◽  
Matrix Surface ◽  
Interface Materials

Measurements and modeling of the thermal resistance of thin (< 100 microns) bond-lines are reported for composite thermal interface materials (TIMs). The composite TIMs consist of alumina particles dispersed in a polymer matrix to form six different adhesive materials. These model TIMs have a common matrix material and are distinguished by their particle size distributions. Bond-lines are formed in a three-layer assembly consisting of a substrate-TIM-substrate structure. The thermal resistance of the bond-line is measured, as a function of bond-line thickness, using the laser flash-technique. A linear variation of resistance with bond-line thickness is observed; Rbl = β · Lbl + Ro. A model is presented that predicts the effective thermal conductivity of the composite as a function of the particle and matrix conductivity, the particle-matrix surface conductance, the particle volume fraction and the particle size distribution. Specifically a method is introduced to account for a broad, continuous size distribution. A particle-matrix surface conductance value of ∼10W/mm2K is found to give good agreement between the measured and predicted effective thermal conductivity values of the composite TIMs.

Double-Sided Transferred Carbon Nanotube Arrays for Improved Thermal Interface Materials

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Andrew J. McNamara ◽  
Yogendra Joshi ◽  
Zhuomin Zhang ◽  
Kyoung-sik Moon ◽  
Ziyin Lin ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Thermal Resistance ◽  
Prolonged Exposure ◽  
Silicon Substrates ◽  
Thermal Interface Materials ◽  
Total Thermal Resistance ◽  
Thermal Interface ◽  
Ir Microscopy ◽  
Vertically Aligned ◽  
Interface Materials

Recently, much attention has been given to reducing the thermal resistance attributed to thermal interface materials (TIMs) in electronic devices, which contribute significantly to the overall package thermal resistance. Thermal transport measured experimentally through several vertically aligned carbon nanotube (VACNT) array TIMs anchored to copper and silicon substrates is considered. A steady-state infrared (IR) microscopy experimental setup was designed and utilized to measure the cross-plane total thermal resistance of VACNT TIMs. Overall thermal resistance for the anchored arrays ranged from 4 to 50 mm2 KW-1. These values are comparable to the best current TIMs used for microelectronic packaging. Furthermore, thermal stability after prolonged exposure to a high-temperature environment and thermal cycling tests shows limited deterioration for an array anchored using a silver-loaded thermal conductive adhesive (TCA).

Silicone Phase Change Thermal Interface Materials: Properties and Applications

2003 ◽  
Author(s):  
S. Mark Zhang ◽  
Diane Swarthout ◽  
Thomas Noll ◽  
Susan Gelderbloom ◽  
Douglas Houtman ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Mechanical Strength ◽  
Phase Change ◽  
Bond Line ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Interface Materials ◽  
Change Material ◽  
Aluminum Mesh

Thermal interface materials (TIM) play a very important role in effectively dissipating unwanted heat generated in electronic devices. This requires that the TIM should have a high bulk thermal conductivity, intimate contact with the substrate surfaces, and the capability to form a thin bond line. In designing new TIMs to meet these industry needs, alkyl methyl siloxane (AMS) waxes have been studied as phase change matrices. AMS waxes are synthesized by grafting long chain alpha-olefins on siloxane polymers. The melting point range of the silicone wax is determined by the hydrocarbon chain length and the siloxane structure. When the AMS wax is mixed with thermally conductive fillers such as alumina, a phase change compound is created. The bulk thermal conductivities of the phase change material (PCM) are reduced as they go through the phase change transition from solid to liquid. By coating the PCM onto an aluminum mesh, both the mechanical strength and the thermal conductivity are drastically improved. The thermal conductivity increases from 4.5 W/mK for the PCM without aluminum support to 7.5 W/mK with the supporting mesh. The thermal resistance of the aluminum-supported sheet at a bond line thickness of 115 microns has been found to be ∼0.24 cm2-C/W. Applying pressure at the time of application has a positive effect on the thermal performance of the PCM. Between contact pressures of 5–80 psi, the thermal resistance decreases as the pressure increases. The weak mechanical strength of the phase change material turns out to be a benefit when ease of rework and the effects of shock and vibration during shipping and handling are considered. A stud pull test of the aluminum mesh-supported PCM shows an average of 13 psi stress at the peak of the break.

Thermal Performance Measurements of Thermal Interface Materials Using the Laser Flash Method

2007 ◽  
Author(s):  
Vinh Khuu ◽  
Michael Osterman ◽  
Avram Bar-Cohen ◽  
Michael Pecht
Keyword(s):  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Composite Structures ◽  
Laser Flash ◽  
Flash Method ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Layer Composite ◽  
Interface Materials

Thermal interface materials are used to reduce the interfacial thermal resistance between contacting surfaces inside electronic packages, such as at the die-heat sink or heat spreader-heat sink interfaces. In this study, the change in thermal performance was measured for elastomeric gap pads, gap fillers, and an adhesive throughout reliability tests. Three-layer composite structures were used to simulate loading conditions encountered by thermal interface materials in actual applications. The thermal resistance of the thermal interface material, including contact and bulk resistance, was calculated using the Lee algorithm, an iterative method that uses properties of the single layers and the 3-layer composite structures, measured using the laser flash method. Test samples were subjected to thermal cycling tests, which induced thermomechanical stresses due to the mismatch in the coefficients of thermal expansion of the dissimilar coupon materials. The thermal resistance measurements from the laser flash showed little change or slight improvement in the thermal performance over the course of temperature cycling. Scanning acoustic microscope images revealed delamination in one group of gap pad samples and cracking in the putty samples.

scholarly journals Prediction of the contact thermal resistance of vertical carbon nanotube arrays

2020 ◽  
Vol 24 (2 Part A) ◽  
pp. 745-756
Author(s):  
Bo Shi ◽  
Han Zhang ◽  
Jin Zhang
Keyword(s):  
Experimental Data ◽  
Surface Roughness ◽  
Carbon Nanotube ◽  
Thermal Resistance ◽  
Interfacial Thermal Resistance ◽  
Nanotube Arrays ◽  
Thermal Interface Materials ◽  
Contact Thermal Resistance ◽  
Carbon Nanotube Arrays ◽  
Interface Materials

The vertical carbon nanotube arrays (VACNT), as a result of its flexibility and axial high thermal conductivity, exert a huge potential and play an increasingly important role in thermal interface materials. This paper proposed a model which can predict the contact thermal resistance of VACNT. The contact thermal resistance of VACNT under different pressures is calculated and compared with the experimental data. Also, the effect of variations in the surface roughness and VACNT parameters on the contact thermal resistance is investigated. Results show that the theoretical results are in good agreement with the experimental data. The contact thermal resistance is composed of interfacial thermal resistance, constriction thermal resistance, and VACNT resistance. Among which the interfacial thermal resistance is the major thermal resistance. The variations in VACNT length and diameter can change the bending degree of VACNT under the same pressure, which presents important implications on contact thermal resistance and can be used to optimize the contact thermal resistance of VACNT. The surface roughness exerts little effect on contact thermal resistance.

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