Torsten Mehlhorn

Intelligent microcooling systems on electronic printed circuit boards

The rapidly rising integration density and clock frequencies of the electronic components and the constantly growing number of functions leads to a integration density and cooling problem in the components on the electronic printed circuit board. This is demonstrated here with the example of transmission techniques in telecommunications. The development of bit rate through glass fiber cables has currently reached the range from 140 Mbit/s to 2.5 Gbit/s and now to 160 Gbit/s. In the solutions applied today, of integration density are exhausted and mechanically complicated. The difficulty of introducing and applying key components quickly, inexpensively, and without the limitations of functionality requires an intelligent and flexible integration method and a new cooling concept like that which is described here.

Flexible and intelligent microcooling systems on electronic printed circuit boards

The rapidly rising integration density and clock frequencies of the electronic components and the constantly growing number of functions leads to an integration density and cooling problem in the components on electronic printed circuit boards. This is demonstrated here with the example of transmission techniques in telecommunications. In the solutions applied today, those of integration density are exhausted and mechanically complicated. The difficulty of introducing and applying key components quickly, inexpensively and without the limitations of functionality requires an intelligent and flexible integration method and a new cooling concept like that which is described here.

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.