Time Domain Thermoreflectance (TDTR) Testing
TDTR testing is a non-contact, laser-based technique that measures the thermal conductivity of materials (particularly thin films). This method can be applied to materials with smooth surfaces and thin films with a thickness range from nanometers to microns.
The idea behind this technique is that a pump laser pulse heats the surface of a material and a subsequent probe laser pulse measures a change in optical reflectivity that is created by the temperature excursion generated by the pump laser pulse. The reflectivity signal is measured as a function of time and the data are analyzed using a heat diffusion model to extract the thermal conductivity .
TDTR testing can be performed over the temperature range from 296 K to 623 K (23 °C to 350 °C).
The requirements for this test are as follows:
- Specimens must have optically smooth surfaces (Mirror-like, ≤15 nm RMS roughness)
- The volumetric heat capacity must be provided for each specimen
Dr. Cahill has partnered with PMIC to offer this testing to customers and performs testing as a subcontractor. David Cahill [at the University of Illinois at Urbana-Champaign] is the Willett Professor of Engineering and Professor of Materials Science and Engineering (MatSE) . He received his Ph.D. in condensed matter physics from Cornell University, and worked as a postdoctoral research associate at the IBM Watson Research Center” .
Figure 1: Time Domain Thermoreflectance (TDTR) Test System .
 D. G. Cahill, “Thermal-conductivity measurement by time-domain thermoreflectance,” MRS Bulletin, vol. 43, no. 10, pp. 782–789, Oct. 2018, doi: 10.1557/mrs.2018.209.
 “Cahill Research Group.” https://cahill.matse.illinois.edu/ (accessed Aug. 24, 2020).
 “David G. Cahill – Cahill Research Group.” https://cahill.matse.illinois.edu/david-cahill/ (accessed Aug. 25, 2020).
 “cahill.thermal,” cahill.thermal. https://cahill-thermal.com/ (accessed Aug. 24, 2020).