scholarly journals Effect of Gamma-Ray Irradiation on the Thermal Contact Conductance of Carbon Nanotube Thermal Interface Materials

2013 ◽  
Author(s):  
Stephen L. Hodson ◽  
Robert A. Sayer ◽  
Timothy P. Koehler ◽  
Justin R. Serrano ◽  
Scott M. Dalton ◽  
...  
Keyword(s):  
Adverse Effects ◽  
Thermal Performance ◽  
Gamma Ray ◽  
Thermal Contact Conductance ◽  
Thermal Interface Materials ◽  
Intrinsic Resistance ◽  
Space Applications ◽  
Thermal Interface ◽  
Gamma Ray Irradiation ◽  
Interface Materials

Thermal interface materials (TIMs) serve a critical role in the thermal management of electronic systems by enhancing the flow of heat from source to sink. Nanostructured materials, such as arrays of carbon nanotubes (CNTs) have been shown to outperform many commercially available TIMs due to their low intrinsic resistance and large compliance that enables them to conform to rough surfaces. These characteristics, combined with their low density and ability to withstand vacuum environments and extreme temperatures, make CNT-based TIMs very suitable for space applications. In space, materials are exposed to high doses of gamma radiation due to the lack of an atmosphere to serve as an absorbing medium. With typical design lifetimes of 5 to 10 years or even more, total radiation exposure can be significant and can affect the structure and performance of the TIM. In this work, the potentially adverse effects on the thermal performance of CNT TIMs of gamma-ray irradiation is reported. CNT TIMs were irradiated in a gamma cell at a rate of 250 rad/s to total doses of 50 and 100 Mrad. The thermal interface resistance was measured before and after gamma-ray irradiation using a transient photoacoustic (PA) method at room temperature and a contact pressure of 134 kPa and indicated no adverse effects of gamma-ray exposure on thermal performance.

scholarly journals Thermal Contact Conductance of Radiation-Aged Thermal Interface Materials for Space Applications

2013 ◽  
Author(s):  
Robert A. Sayer ◽  
Timothy P. Koehler ◽  
Scott M. Dalton ◽  
Thomas W. Grasser ◽  
Ronald L. Akau
Keyword(s):  
Gamma Ray ◽  
Thermal Contact ◽  
Critical Role ◽  
Space Mission ◽  
Thermal Contact Conductance ◽  
Thermal Interface Materials ◽  
Space Applications ◽  
Thermal Interface ◽  
Satellite Systems ◽  
Interface Materials

Thermal interface materials (TIMs) serve a critical role in thermal management by enhancing heat transfer across contact interfaces. Specifically, they are most commonly used in electronics to enhance the flow of heat from source to sink by decreasing the overall thermal resistance of the system. In space, these materials are exposed to high doses of Gamma radiation due to the lack of an atmosphere to serve as an absorbing medium. With typical design lifetimes of 5 to 10 years, total radiation exposure can be significant and can adversely affect the thermal contact resistance (TCR) of the TIM. In this manuscript, we report the effect of radiation-aging on the TCC of several commercially available electrically insulating, thermally conductive interface materials that are commonly used in satellite systems. Although radiation dose levels can vary significantly during the course of a space mission, a dosing of 10 Mrad per year for TIMs is a reasonable estimate. The TIMs were aged in a Gamma cell at a rate of 250 rad/s to total doses of 50 and 100 Mrad to simulate mission lengths of 5 and 10 years, respectively. The TCR of each radiation-aged sample, as well as un-aged samples, were measured under vacuum (less than 3 × 10−4 Pa). Radiation-aging of the TIMs led to a significant increase in the TCR of the tested samples. For example, the pressure-dependent TCR was shown to increase 20–150% for Cho-Therm 1671 and 50–250% for ThermaCool R10404 samples subjected to 50 Mrad of gamma-ray irradiation. These results show that radiation-aging of TIMs cannot be ignored in the design and simulation of space systems.

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.

Mechanical Insertion and Reliability Testing of Thermal Interface Materials for Semiconductor Test and Burn-in Applications

2018 ◽  
Vol 2018 (1) ◽  
pp. 000613-000618
Author(s):  
Dave Saums ◽  
Tim Jensen ◽  
Carol Gowans ◽  
Seth Homer ◽  
Ron Hunadi
Keyword(s):  
Thermal Performance ◽  
Mechanical Performance ◽  
Device Under Test ◽  
Thermal Interface Materials ◽  
Reliability Testing ◽  
Mechanical Reliability ◽  
Thermal Interface ◽  
Cycling Test ◽  
Semiconductor Test ◽  
Interface Materials

Abstract Semiconductor test and burn-in requirements for thermal interface materials (TIMs) are challenging, with difficult mechanical reliability requirements that are not found in other types of applications for these materials. To demonstrate the ability of certain newly-developed TIMs to not only provide suitable thermal performance for the device under test and meet these mechanical requirements, a contact cycling test has been devised in three phases for evaluating TIM mechanical performance and durability.

Thermal and Mechanical Properties of Silicone Thermal Interface Materials With Varying Cross-Link Densities

2005 ◽  
Author(s):  
Arun Gowda ◽  
Annita Zhong ◽  
Sandeep Tonapi ◽  
Kaustubh Nagarkar ◽  
K. Srihari
Keyword(s):  
Mechanical Properties ◽  
Thermal Performance ◽  
Cross Linking ◽  
Thermal Interface Materials ◽  
Material System ◽  
Thermal And Mechanical Properties ◽  
Thermal Impedance ◽  
Operating Life ◽  
Thermal Interface ◽  
Interface Materials

Thermal Interface Materials (TIMs) play a key role in the thermal management of microelectronics by providing a path of low thermal impedance between the heat generating devices and the heat dissipating components (heat spreader/sink). In addition, TIMs need to reliably maintain this low thermal resistance path throughout the operating life of the device. Currently, several different TIM material solutions are employed to dissipate heat away from semiconductor devices. Thermal greases, adhesives, gels, pads, and phase change materials are among these material solutions. Each material system has its own advantages and associated application space. While thermal greases offer excellent thermal performance, their uncured state makes them susceptible to pump-out and other degradation mechanisms. On the other hand, adhesives offer structural support but offer a higher heat resistance path. Gels are designed to provide a level of cross-linking to allow the thermal performance of greases and prevent premature degradation. However, the degree of crosslinking can have a significant effect of the behavior of gels. In this research, TIMs with varying cross-linking densities are studied and their thermal and mechanical properties reported. The base resin systems and fillers were maintained constant, while slight compositional alternations were made to induce different degrees of cross-linking.

Durability of Low Melt Alloys as Thermal Interface Materials

2016 ◽  
Vol 138 (1) ◽  
Author(s):  
Chandan K. Roy ◽  
Sushil Bhavnani ◽  
Michael C. Hamilton ◽  
R. Wayne Johnson ◽  
Roy W. Knight ◽  
...  
Keyword(s):  
Thermal Performance ◽  
Performance Testing ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
High Performing ◽  
Accelerated Life ◽  
Significant Performance ◽  
Interface Materials ◽  
Temperature Aging

This study investigates the reliability of low melt alloys (LMAs) containing gallium (Ga), indium (In), bismuth (Bi), and tin (Sn) for the application as Thermal interface materials (TIMs). The analysis described herein involved the in situ thermal performance of the LMAs as well as performance evaluation after accelerated life cycle testing, which included high temperature aging at 130 °C and thermal cycling from −40 °C to 80 °C. Three alloys (75.5Ga & 24.5In, 100Ga, and 51In, 32.5Bi & 16.5Sn) were chosen for testing the thermal performance. Testing methodologies used follow ASTM D5470 protocols and the performance of LMAs is compared with some high-performing commercially available TIMs. Results show that LMAs can offer extremely low (<0.01 cm2 °C/W) thermal resistance compared to any commercial TIMs. The LMA–substrate interactions were explored using different surface treatments (copper and tungsten). Measurements show that depending on the substrate–alloy combinations, the proposed alloys survive 1500 hrs of aging at 130 °C and 1000 cycles from −40 °C to 80 °C without significant performance degradation. The obtained results indicate the LMAs are very efficient as TIMs.

Thermomechanical Degradation of Thermal Interface Materials: Accelerated Test Development and Reliability Analysis

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Hayden Carlton ◽  
Dustin Pense ◽  
David Huitink
Keyword(s):  
Thermal Performance ◽  
Structural Integrity ◽  
Void Formation ◽  
Conductivity Measurement ◽  
Cyclic Stress ◽  
Thermal Interface Materials ◽  
Interfacial Resistance ◽  
Thermal Interface ◽  
Mechanical Cycling ◽  
Interface Materials

Abstract Due to the inherently low adhesive strength and structural integrity of polymer thermal interface materials (TIMs), they present a likely point of failure when succumbed to thermomechanical stresses in electronics packaging. Herein, we present a methodology to quantify TIM degradation through an accelerated and repeatable mechanical cycling technique. The testing apparatus incorporated a steady-state thermal conductivity measurement system, consistent with ASTM 5470-06, with added displacement actuation and force sensing to provide controlled cyclic loading between −20 N and 20 N. Additionally, a novel optical technique was utilized to observe void formation, pump-out, and dry-out behavior during cycling, in order to correlate the thermal performance with physical behaviors of different TIMs under cyclic stress. Of the two different pastes analyzed, cyclic testing was found to degrade the thermal performance of the less viscous TIM by increasing its interfacial resistance. Optical qualitative measurements revealed the breakdown of the TIM structure at the interface, which indicated the formation of voids due to TIM degradation. Applying this testing method for future TIM development could help in optimizing TIM structure for particular package applications.

Thermo-Mechanical Degradation of Thermal Interface Materials: Accelerated Test Development and Reliability Analysis

2019 ◽  
Author(s):  
Dustin Pense ◽  
Hayden Carlton ◽  
David Huitink
Keyword(s):  
Thermal Performance ◽  
Structural Integrity ◽  
Mechanical Degradation ◽  
Thermal Interface Materials ◽  
Interfacial Resistance ◽  
Thermal Reliability ◽  
Thermal Interface ◽  
Static Test ◽  
Mechanical Cycling ◽  
Interface Materials

Abstract Thermal interface materials (TIMs) comprise an important role in the thermal management of a myriad of electronic devices, and their ability to ensure both enhanced thermal conductance and reliable adhesion at thermal interfaces is paramount to the reliability of electronics packaging. Like most aspects of a typical electronics package, on/off cycles undergone during a device’s operation induce thermo-mechanical stresses that can negatively affect the integrity of the package. Due to the inherently low adhesive strength and structural integrity of polymer TIMs, they present a likely point of failure when succumbed to these interfacial stresses. Methods for quantifying TIM degradation during mechanical cycling have been quite infrequent in literature; an accelerated and repeatable method for measuring the thermal reliability of TIMs would prove to be beneficial. Herein, we present a methodology to quantify the thermal reliability of TIMs during mechanical cycling using a custom-built steady-state thermal conductivity tester. Additionally, an optical technique was utilized to observe void formation, pump-out, and dry-out behavior during cycling, in order to correlate the thermal performance with physical behaviors of the TIM under cyclic stress. After an initial long-term static test, cyclic testing was found to degrade the thermal performance of the TIM through increasing its interfacial resistance. Optical qualitative measurements revealed the breakdown of the TIM structure at the interface, which indicated the formation of voids due to TIM degradation. Applying this testing method for future TIM development could help in optimizing TIM structure for particular package applications.

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