Printed circuit board with feedback controlled internal water cooling

When integrating a micro cooling system into an electronic device there are two basic options for assembly of cooling system and PCB: external attachment of the cooling system onto a component-free PCB side; and complete integration into the PCB interior. The first option may be suitable for first tests but has serious drawbacks as a final solution (e.g. one PCB side is lost for component allocation). The second option is considered optimal since its advantage of a heavily improved heat balance control offers immediately a higher (double sided) component density. The first crucial point of our activities aimed at the generation of defined cavities within the interior of a multi layer PCB. The second crucial point is the minimization of the heat-transmission resistance between PCB surface and channel system. The third crucial point is the investigation of different options of drives for the coolant. The starting point for systematic construction of cavities within PCBs is a three-layer structure. An extremely thick copper layer is used as an internal heat sink. For that purpose a double-sided base laminate with 400 /spl mu/m copper is made as an internal heat sink which is joined later with a prepreg and a copper foil to form a 3-layer structure.