Thermal characterization of liquid and solid samples using a measurement platform for the bidirectional 3-omega method

Measuring the thermal conductivity can be challenging, especially for liquids or pastes of small volumes. We developed a measurement chip which is suitable for a rapid, accurate and convenient determination of the thermal conductivity and diffusivity of droplet size specimens [1]. The measurement method is based on an extension of the 3-omega measurement technique, the so-called bidirectional 3-omega method [1,2]. We designed and fabricated a characterization chip with through-glass vias allowing for the measurement of small samples, a convenient sample positioning and optical inspection of the sample during measurement. A very thin passivation layer, fabricated by atomic layer deposition, enables measuring electrically conductive samples while maintaining good thermal transport through the passivation layer. Sample volumes down to 0.02 mm³ are sufficient for accurate measurements. The measurements can be performed within few minutes. Measurements of the thermal conductivity of different thermal interface materials, for example, pastes and pads, and several liquids and polymers, were performed and the results are compared to those obtained using a standard steady-state technique and literature values. The results obtained with both methods agree well showing that the bidirectional 3-omega method is suitable for the thermal characterization of such samples.