| 摘要 |
ESD events on a hybrid circuit are suppressed with a high performance spark gap cut in a metal trace with a suitable laser micro machining technique. The trace can be carried by a conventional printed circuit board (using FR4), or a ceramic substrate. Gap size is reduced by flushing the cut with a flow of gas that removes the vaporized copper and prevents it from re-depositing upon the cut surfaces and bridging them. The gap can be as narrow as 0.4 mils (0.0004 inches) and can have very well defined features that include sharp corners that assist in lowering the breakdown voltage. In addition, dielectric material below and off to either side of the trace that would otherwise adjoin the metallic gap can also be removed, which lowers breakdown voltage and decreases capacitance across the gap. Breakdown voltages as low as 300 V can be achieved. Such a spark gap is used at the probe tip of an active oscilloscope probe to protect the delicate circuitry therein.
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