The characteristics of ultra-thin multilayers (UTM) are laminates or prepregs with a thickness of just 50µm or less. For the processing of such materials a special technology is needed, offered only from a small number of expert firms. Besides its minimum thickness, UTM offers the advantage of excellent EMC qualities. The very low distance between single layers, and therefore the capacitive property of the power planes, leads to improved wideband decoupling. For impedance-controlled multilayers, a differentiated capacity between VCC and GND can be achieved by intelligent layer selection. This provides for the designer, especially in case of high-speed circuits, the opportunity of variations in the definition of line spacing and size to accomplish rated impedance. The design of UTMs with 8 or 10 layers does not only allow for the realization of micro striplines, but also of dual striplines, and UTM complies fully with the ongoing trend of miniaturization. This can be an advantage in mobile appliances, for stacked assembly of MCMs or in case of extremely tight housing issues. ILFA, one of the leading UMTS protagonists, has not only high expertise as manufacturer of such PCBs, but also provides comprehensive information about CAD design rules for free-of-charge download.
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