Thermal Transport and Mechanical Stress Mapping of a Compression Bonded GaN/Diamond Interface for Vertical Power Devices.

Bonding diamond to the back side of gallium nitride (GaN) electronics has been shown to improve thermal management in lateral devices; however, engineering challenges remain with the bonding process and characterizing the bond quality for vertical device architectures. Here, integration of these two materials is achieved by room-temperature compression bonding centimeter-scale GaN and a diamond die via an intermetallic bonding layer of Ti/Au. Recent attempts at GaN/diamond bonding have utilized a modified surface activation bonding (SAB) method, which requires Ar fast atom bombardment immediately followed by bonding within the same tool under ultrahigh vacuum (UHV) conditions.

Inversion for Thermal Properties with Frequency Domain Thermoreflectance.

3D integration of multiple microelectronic devices improves size, weight, and power while increasing the number of interconnections between components. One integration method involves the use of metal bump bonds to connect devices and components on a common interposer platform. Significant variations in the coefficient of thermal expansion in such systems lead to stresses that can cause thermomechanical and electrical failures.

A multi-frequency 3ω method for tracking moving phase boundaries.

A technique has been developed to track a moving phase front using the electrothermal 3ω method and demonstrated by tracking the location of the phase boundary between air and dielectric oil. A fine wire 3ω sensor (diameter 10 µm, length 30 mm) is suspended in oil and excited at four frequencies simultaneously to gain more thermal information than a single-frequency approach. Measurements of the phase boundary location are compared to camera images to verify their accuracy.

A Micro-Thermal Sensor for Focal Therapy Applications.

There is an urgent need for sensors deployed during focal therapies to inform treatment planning and in vivo monitoring in thin tissues. Specifically, the measurement of thermal properties, cooling surface contact, tissue thickness, blood flow and phase change with mm to sub mm accuracy are needed. As a proof of principle, we demonstrate that a micro-thermal sensor based on the supported "3ω" technique can achieve this in vitro under idealized conditions in 0.