Abstract
Polymer films are playing an important role in the development of fast integrated circuits, novel micromachined sensors and actuators, organic optoelectronic devices, and advanced packaging and underfill structures. The low thermal conductivities of polymer layers yield large temperature rises and temperature gradient magnitudes that strongly influence performance and reliability. This work develops three experimental techniques for measuring both the in-plane and out-of-plane thermal conductivities of spin-coated polyimide films of thicknesses between 0.5 and 2.5 μm and at temperatures between 260 and 360 K. Two of the techniques use transient electrical heating and thermometry in micromachined structrures to isolate the in-plane and out-of-plane components. These techniques are used to establish confidence in a third, simpler technique, which is fully IC compatible micromachining and measures both components independently. The data illustrate anisotropy in the thermal conductivity of the polymide films investigated here, with the in-plane conductivity larger by a factor between 4 and 8 depending on thickness and temperature.
