Micro gap method and ESD protection device

Abstract

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.

Description

technical field [0001] The invention relates to a micro-gap method and an electrostatic discharge protection device. Background technique [0002] Active probe assemblies for high-frequency oscilloscopes require a small form factor, for reasons such as the wavelength of the highest frequency in the "oscilloscope's" bandwidth. Therefore, the coupling and matching network that connects the tip(s) of the actual probe to the input(s) of the preamplifier often has a low profile. The resistive elements in these coupling and matching networks are considerably limited in their ability to dissipate energy and, in addition to thermal effects, can experience significant permanent changes in value due to exposure to electrostatic stress. [0003] In addition, the active devices in this probe assembly are typically found in integrated semiconductor amplifier assemblies, which are often susceptible to damage and destruction from ESD, or electrostatic discharge (i.e., they can be "zapped"...

AI Technical Summary

Problems solved by technology

But the trick will be to be able to reliably make such small spark gaps in product tuning

[0010] The typical breakdown voltage of 1.5KV to 2KV currently used for conventional spark gaps often does not provide adequate protection

In addition, the tight tolerances required to fabricate smaller gaps are difficult or impossible to maintain with photolithography, and various problems have plagued laser technology to date, preventing the economical use of cutting smaller gaps in metal traces. of commercial products

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