A Stepped-Bar Apparatus for Thermal Resistance Measurements

Thompson, Dakotah; Rao, Sameer R.; Cola, Baratunde A.

doi:10.1115/1.4025116

Cited by 33 publications

(18 citation statements)

References 12 publications

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“…With a temperature measurement location uncertainty of only 20 p, m (when considering the uncertainty in the hole diameter alone), the authors find that the maximum possible resolu tion for the device (with 10 % engineering uncertainty) is rv 5·1O-6 m 2 ·KIW. A similar approach has been taken in previous work [26].…”

Section: Introductionmentioning

confidence: 88%

“…Despite these promising results, there has been some debate about the true rigor of the methods used to calculate the uncertainty of llTinter face [13], [14], [26]. For instance, the authors of the present work are aware of only one study that attempts to determine the uncertainty of II Tinter f ace as a function of the number of thermocouples that are embedded within each heat meter bar [26].…”

Section: Introductionmentioning

confidence: 90%

“…?, it can be substantially more accurate to use as many thermocouples as possible to project the temperature at each interface by evaluating the slope of a linear regression through the ensuing temperature/position distribution on each heat meter bar (assuming that heat flow is strictly one-dimensional and that the thermocouples are evenly spaced). A few groups have already used this method to calculate both the thermal resistance across the interface and the uncertainty in this calculation [21], [26], while others have either used this method to calculate the temperature difference across the interface, but not the uncertainty in their calculation of �Tinter j ace [14], [30] or have favored the ASTM methodology altogether [31]- [34]. While it is likely that the linear regression methodology used in [21], [26], [30] is likely to be more accurate, the relative uncertainty for each methodolgy at different values of Rc has not been compared.…”

Section: B Comparison Of Astm Methodology With Linear Regression Anamentioning

confidence: 99%

“…Alternatively, several groups utilize a slightly different approach to determine Tel and Tc2 [26]. In this alternative approach, the temperature at each side of the interface is determined by utilizing a linear regression that passes through each temperature measurement location.…”

Section: A Calculation Of Inteifacial Thermal Resistancementioning

confidence: 99%

“…For instance, the authors of the present work are aware of only one study that attempts to determine the uncertainty of II Tinter f ace as a function of the number of thermocouples that are embedded within each heat meter bar [26]. In their work, Kempers et al [14] only consider the uncertainty in the location of each temperature measurement as it relates to the first and last thermal probe in each heat meter bar (Eqns.…”

Section: Introductionmentioning

confidence: 99%

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Improved methodology for calculating interfacial thermal resistance and uncertainty for steady-state TIM testers with embedded probes

Warzoha

Smith

Harris

2016

2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)

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Abstract-Efforts to miniaturize electronic components within the semiconductor industry continue to intensify stresses on the primary thermal pathways that are used for heat dissipation in electronics packaging equipment. This is particularly true for heat flow pathways that traverse interfaces. Consequently, an increasing priority for thermal engineers is to design materi als that are capable of reducing the impedance to heat flow acrosss device junctions. However, the equipment most often used to measure the resistance to heat flow across interfaces (ASTM D5470) is becoming increasingly insufficient for the characterization of next-generation thermal interface materials (TIMs) , as evidenced by the wide variability in the reported results for current state-of-the-art TIMs. Through the use of statistical analyses, we show that one possible reason for these discrepancies is the method by which the temperature difference across the interface is calculated. Additionally, we find that there exists a lack of consideration for many potential sources of positional uncertainty that exist within the measurement system, including: 1) the thermal conductivity mismatch between the thermal probes, the heat meter bars and any interstitial filler material used to increase contact conductance between them, 2) drill drift during manufacturing, 3) the temperature and positional uncertainties of each probe along the length of the heat meter bars, 4) the tolerance associated with the location of each thermal probe's junction and 5) the number of thermal probes that are used to determine the temperature difference across the interface. We find that these factors result in an unavoidably large uncertainty in the position of the thermal probes, which produces a significant measurement uncertainty when RT is on the order of 1.10-5 m 2 ·KJW or lower, regardless of the temperature measurement accuracy that can be achieved with the probes. Using numerical simulations, we conduct a parametric study to determine the magnitude of these effects on positional uncertainty. Results suggest that the lowest positional uncertainty is achieved when the thermal probe is significantly less thermally conductive than its surrounding filler, and that drill drift and the uncertainty associated with the location of the actual thermal probe junction account for a significant increase in the overall uncertainty of the measurement. It is expected that these results will allow for the development of steady-state TIM characterization instruments with improved measurement resolutions and for greater consistency between the results of different groups that use thermal probe-based TIM testers.

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Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 90%

Section: B Comparison Of Astm Methodology With Linear Regression Anamentioning

confidence: 99%

Section: A Calculation Of Inteifacial Thermal Resistancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Improved methodology for calculating interfacial thermal resistance and uncertainty for steady-state TIM testers with embedded probes

Warzoha

Smith

Harris

2016

2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)

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Thermal Conductivity Enhancement of Soft Polymer Composites through Magnetically Induced Percolation and Particle–Particle Contact Engineering

Ralphs

Kong

Wang

et al. 2019

Adv Materials Inter

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Despite major advancements in the performance of thermal interface materials (TIMs), contact resistance between components persists as a major thermal bottleneck in electronics packaging. In this work, the thermal performance of composite TIMs is enhanced through a synergistic coupling of magnetic alignment and engineered particle coatings that reduce the thermal resistance between particles. By itself, magnetically induced percolation of nickel particles within a cross‐linked silicone matrix doubles the thermal conductivity of the composite. This process significantly increases contact between particles, making the interfacial particle–particle resistance a major contributor to the composites thermal performance. The resistance at these interfaces can be reduced by introducing soft metal (silver) or liquid metal coatings onto the nickel particles. Compressing powder beds of these hybrid particles reveals that, dependent on coating thickness, the contact engineering approach provides multifold increases in thermal conductivity at mild pressures. When dispersed in a polymer matrix and magnetically aligned, the coated particles provide a threefold increase in composite thermal conductivity, as compared to unaligned samples (up to nearly 6 W m−1 K−1 with volumetric fill fraction of 0.5). For equivalent coating thicknesses, silver coatings achieve better performance than liquid metal coatings.

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Precuring Matrix Viscosity Controls Thermal Conductivity of Elastomeric Composites with Compression‐Activated Liquid and Solid Metallic Filler Networks

Uppal

Kong

Rana

et al. 2023

Adv Materials Inter

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high-performance electronic devices, soft robotics, and flexible electronics. These materials ensure that devices reliably function by reducing thermal resistance between the heat-generating components and the cooling solutions. [1][2][3][4][5] Specifically, the inherent microroughness and imperfect contact at component interfaces leads to large thermal resistances. In order to function, TIMs need high thermal conductivity and good wettability to remove heat. TIMs also need to be mechanically compliant to overcome dynamic warpage of the mating surfaces. [6,7] This dynamic warpage arises due to the combined effects of thermal cycling and mismatches in thermal expansion of adjacent components. This temperature-induced dynamic warpage causes fluid-phase TIMs (e.g., silicone greases), to pump out of the interface, which in turn leads to a high thermal resistance and overheating. The inability to pump out of an interface is one of the advantages of solid-phase TIMs. Crosslinked polymers offer appropriate mechanical properties for solid-phase TIMs, but have a low thermal conductivity of 0.2-0.3 W m −1 K −1 . [8][9][10] To overcome this problem, high thermal conductivity rigid filler materials (alumina, copper, graphene, boron nitride, etc.) [11][12][13][14][15][16] are incorporated into the precursor polymer solution prior to crosslinking. A curing process is then used to crosslink the precursor polymer solution and create a solid polymer composite TIM pad. A high volume fraction of rigid filler particles substantially enhances the composite thermal conductivity by creating multiple percolation paths, but also causes detrimental stiffening of the polymer. [7] In addition, curing polymers with very high solid additive content results in pads that "crumble" and are not suitable for TIM applications. [6,17,18] In contrast, liquid fillers can be incorporated into polymer composites as microdroplets at high volume fractions without degrading the mechanical properties. [19][20][21] Liquid metals (LMs) based on Ga (e.g., elemental Ga, eutectic GaIn, and eutectic GaInSn) have sufficient thermal conductivity and mechanical compliance to function as TIMs, but present other challenges due to their reactive/corrosive properties. Consequently, LMs are typically used as fillers within polymer composites such that the polymer functions as a physical barrier that prevents corrosion between the TIM and Polymer matrix composites with liquid metal droplet and solid particle fillers are promising candidates for thermal interface materials (TIMs) used in electronics thermal management. To achieve good thermal transport, the particle and droplet fillers must be interconnected to form thermally conductive percolation pathways in the polymer matrix. This in turn requires displacement of the polymer between fillers as well as rupture of the oxide shell on the liquid metal droplets. This study demonstrates a multipronged strategy to achieve extensive filler bridging and a high thermal conductivity polymer TIM pad. The strategy synergistically e...

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A Stepped-Bar Apparatus for Thermal Resistance Measurements

Cited by 33 publications

References 12 publications

Improved methodology for calculating interfacial thermal resistance and uncertainty for steady-state TIM testers with embedded probes

Improved methodology for calculating interfacial thermal resistance and uncertainty for steady-state TIM testers with embedded probes

Thermal Conductivity Enhancement of Soft Polymer Composites through Magnetically Induced Percolation and Particle–Particle Contact Engineering

Precuring Matrix Viscosity Controls Thermal Conductivity of Elastomeric Composites with Compression‐Activated Liquid and Solid Metallic Filler Networks

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