Thermal conductivity characterization of an in-house formulated thermal insulating xerogel - epoxy composite adhesive for electronics applications

The thermal conductivity data provided by the manufacture are not always sufficiently accurate, and not available for newly formulated materials . However, it is crucial to obtain precise data of the thermal conductivity for low (less as 0.2 W m-1 K-1) thermal conductivity materials where measurement errors have significant impact. There are several experimental methods to measure the thermal conductivity of insulating materials. These methods can be generally divided in two broad groups: steady-state and transient methods. In our work, we compared the results of thermal conductivity obtained by 3 different methods for the in-house formulated thermally insulating xerogel - epoxy composite adhesive. We performed the steady-state thermal conductivity measurements in vacuum chamber with low pressure of 7 10-9 mbar to suppress the conduction and convection losses. The results obtained by that method were compared with data obtained using two transient methods, a laser flash analysis (LFA) and an infrared (IR) thermography method. The LFA and IR thermography are indirect methods and require at least three independent measurements to obtain the thermal conductivity. The measurements error is larger than for the steady-state method. Additionally, to that, the IR thermography method exhibits several practical complications to realize necessary conditions of thermal transfer. That results in possible measurements errors and makes it not possible to obtain the thermal conductivity accurately. The steady-state and LFA methods can be used for the characterization of the thermal conductivity for low thermal conductivity materials such xerogel-epoxy composites