Improving heat transfer performance of printed circuit boards

There is a trend continuing in the electronics industry where high reliability electronic packages are using standard epoxy glass and polyimide substrates over ceramic based substrates. This is a result of improved fabrication accuracy and consistent raw material properties. Increased processing power is resulting in increased heat generation. Printed circuit boards are becoming very dense as a result of improved fabrication processes that allow smaller vias, smaller trace line width/spaces and pad size. This is combined with designs that have multiple internal conductive layers that routinely reach 20 to 25 layers. This increased processing power is affecting printed circuit board designs for space electronic applications. The additional heat must be conducted from a microprocessor or power device through the printed circuit board to the board frame or chassis. This has been achievable for processing devices by utilizing thick copper layers and thermal vias to transfer the resultant heat. The result of increasing the copper thickness is an increase in mass which is an undesirable condition where the goal for electronics is a smaller and lighter electronic package.