The present invention relates to circuit boards and, more specifically, circuit boards with vias exhibiting reduced via capacitance.
A via is a common structure in a circuit board used to connect transmission traces, such as strip-line or micro-strip traces, formed on different layers of the circuit board. A via is typically realized by drilling a hole through the traces to be connected, and plating the via with electrically conductive material such as copper. The width of the traces, for example between 4 micro inches (MIL) and 7 MIL, is smaller than the width of the electrically conductive material on the via. The example numerical range provided for the width of the traces is an approximate numerical range only, and the present invention is not limited to traces with a width within this numerical range. Because of this difference in physical dimension, the via is plated with more electrically conductive material than the traces it interconnects. The excess electrically conductive material on the via tends to create excessive capacitance, resulting in impedance discontinuity in signal transmissions between traces interconnected using the via.