Development of a high-accuracy thermal interface material tester

Abstract

An experimental apparatus has been designed and constructed to accurately measure the next generation of high-performance thermal interface materials with unprecedented precision and accuracy.The apparatus is based on a common implementation of ASTM D5470 using meter bars. However, the apparatus in the present study is unique in that it utilizes small thermistors to make precise thermal measurements (±0.003 K). These measurements are used to calculate the thermal impedance at the interface of two conducting bodies while keeping input power at a minimum. Furthermore, a robust and conservative uncertainty analysis is employed to calculate how the measured uncertainties contribute to the calculated quantities of thermal impedance and effective thermal conductivity.Baseline tests are performed to demonstrate the sensitivity and uncertainty of the apparatus by measuring the contact resistance of the meter bars in contact with each other as a representative low-thermal-impedance case. A contact thermal impedance as low as 2.81E-5 m 2 ·K/W was measured with a calculated absolute uncertainty of approximately 2%. The effective thermal conductivity of a gap pad was also measured to further validate the apparatus.

Characterization of Metallically Bonded Carbon Nanotube-Based Thermal Interface Materials Using a High Accuracy 1D Steady-State Technique

“…A thorough but conservative uncertainty analysis similar to Ref. [21] using the Brown, Coleman, and Steele methodology [23] predicts a measurement uncertainty of 15% or lower for thermal resistances as low as 4 mm 2 K/W. The main drivers of experimental uncertainty are thermistor hole location measurements along the length of the meter bars and float of the thermistors in their holes due to diametric clearance.…”

“…Facility. Because carbon nanotube-based thermal interface materials have the potential to provide thermal resistances an order of magnitude lower than current commercially available solutions, their characterization requires an innovative testing approach, with precision similar to those approaches utilized by others measuring very low resistance materials [20,21]. Our solution involved the design of a test facility tailored to the characterization of these new nTIMs, allowing the accurate measurement of thermal resistances down to 4 mm 2 K/W or better and capturing the interface physics resulting from CTE-mismatched semiconductors and packaging materials.…”

Thermal management: Enabling enhanced functionality and reduced carbon footprint

“…The measurement sensitivity of the TIMs test apparatus was evaluated using self-contact resistance tests and showed the ability to accurately measure very low thermal contact resistances (6e-5 m 2 K/W) with better than 2 percent uncertainty and low input power levels of 10 W. These baseline measurements showed a degree of precision and sensitivity heretofore not achieved in previous test setups, and clearly demonstrated the ability of the apparatus to test even the thinnest, most conductive TIMs with good confidence [6]. Figure 6 illustrates the performance comparison between commercially available graphite pads and novel metallic micro-textured TIMs.…”

Degradation characterization of thermal interface greases

“…Their use of a symmetrical design, heater cartridges and a cold plate with Peltier cells, allowed for the capability of reversing the heat flow through the sample. Kempers et al quantified the uncertainty of each measured quantity within their D5470 test setup and used thermistors for thermal measurement [12]. Xu and Fisher used the technique to quantify the thermal contact conductance enhancement by the use of carbon nanotube (CNT) arrays [13].…”