Session: IMECE Undergraduate Research and Design Exposition

Paper Number: 113881

113881 - Methods to Characterizing Thermal Properties of Microchip Packaging Materials: Quantitative Analysis of Niobium, Copper, Sapphire and Silicon Nitride Using Cryogenic Cycling 

Low temperature behavior has been evaluated for a limited set of materials including copper (Cu) and aluminum (Al); however, some materials such as niobium (Nb) have low property data. With newer microchip circuit materials, there is a scarcity of precise thermal property data in the specified cryogenic temperature range of 77K to 4K. Dependable cryogenic temperature thermal property data are critical in material selection and thermal design of engineered systems in the microelectronics sector. Microchip circuitry is a system of linked materials that include the chip, substrate, and printed circuit board (PCB). These circuits frequently undergo substantial temperature cycling that induce thermo-mechanical stresses among material boundary layers, resulting in critical fatigue and premature failure. The effects of cryogenic temperatures on thermal expansion, thermal conductivity, electrical resistivity, residual resistance ratio (RRR), and superconducting transition temperature for microchip packaging materials are investigated experimentally in this study.

This study experimentally validates the effects of cryogenic thermal cycling ranging from room temperature to 4K, on electronic packaging materials, niobium and copper. With niobium having the highest superconducting transition temperature, 9.32 K, of all pure metals, it may be able to withstand the consistent changes in temperature as it is thermally stable. For our experiment, we used the cutbar method which sandwiches the unknown material, niobium, between known materials, copper and aluminum, as well as using liquid nitrogen as our cryogen to cycle the temperature down 4K. Furthermore, the DAC, a digital to analog converter which includes the temperature controller, gives information about the entire system’s temperature which can be then translated to MATLAB. The three temperatures obtained from the cut bar system as shown in Figure 2, the temperature of the surface near the heater (T1), the temperature near the cold mount, copper, (T2), and the temperature between the known and the unknown (T3).

Using the information about temperature recorded from MATLAB, Fourier’s Law, we are able to plug in the watts of the system, length of the material, and area in order to find the thermal conductivity. The three temperature sensors give data for the temperature and the DAC collects the data about the local heat flux density. In testing, when there was a temperature decrease of 1.5 degrees Celsius, the thermal conductivity of Niobium was recorded to be 393.7007874 W/m·K. A temperature decrease of 2.8 degrees Celcius was recorded to produce a thermal conductivity of 175.7592801 W/m·K. Our findings suggest that with an increase in temperature change, there is an increase in thermal conductivity. Our continuous flow cryostat system and associated measurement methods will provide an accurate means of monitoring the thermal characteristics of these substrates and sample materials.

Presenting Author: Sadiyah Anderson Howard University

Presenting Author Biography: Sadiyah Anderson is an undergraduate research assistant at the Applied Fluids Thermal Research Laboratory (@FTERLab). Currently, she is majoring in biology and minoring in chemistry.

Authors:

Sonya Smith Howard University
Sadiyah Anderson Howard University