High Thermal Conductive Adhesive Sheet with Low Dielectric Constant

High thermal conductive adhesive sheet whose dielectric constant (Dk) is 5.0 was developed. To obtain low Dk. low Dk matrix polyimide resin whose Dk is 2.6 was designed to decrease Dk as much as possible. To obtain high thermal conductivity, h-BN sphere shaped filler was used as a main heat thermal conductive filler. The h-BN sphere shaped filler shows high thermal conductivity (40W/mK) as bulk filler and low Dk (4.0). High thermal conductive adhesive was obtained by mixing the h-BN cohesive filler into the low Dk polyimide matrix resinIn addition, to make heat path in the high thermal conductive adhesive to z-direction, AlN whisker was oriented to z-direction in the thermal conductive adhesive. We successfully developed novel method to disperse AlN whiskers to z-direction preferably. By utilizing the alignment method, thermal conductivity of the materials increased drastically.As a result, the heat conductive sheet shows the heat conductivity of 15W/mK with low dielectric constant. In addition, the sheet shows excellent break down voltage. The adhesive sheet is suitable for Thermal Interface Material (TIM) for high voltage power modules.