Computer aided optimization of advanced materials for liquid cooled printed circuit boards and their use in telecommunications

Due to the demand for short signal running times the HF-technology requires high integration densities of active components. This results in considerable thermal problems additionally enlarged by the steady rising tact frequencies (up to 80 Gbits/s). Thus usual layouts for telecommunication purposes show hot spots with high temperature gradients. A consequence of local temperature elevations is a drastically reduced component life time. Thermally induced stresses caused by the high temperature gradients are a further failure source. In combination with more thermal cycles per time unit these mechanical strains and stresses cause a considerable reduction of life time, too. Numerical parameter studies of various board materials have shown, that a properly heat conducting and efficiently cooled board is a promising measure to reduce the component stresses by decreasing and equalizing the component temperatures. Using aluminium as the board material under the same conditions a lower operation temperature can be achieved with the effect of increasing the life time. Otherwise, the integration density can be increased to get better HF-properties. The dielectric is an anodic oxide (Eloxal). The thickness ratio between it and the aluminium substrate has been optimized numerically. The presentation deals with the choice of the new board material from thermal, thermomechanical and environmental viewpoints. A first demonstrator for the interconnection technology on anodically oxidized aluminium already exists and is presented.