High-frequency signals on ground is never good news - it interferes with normal operation of equipment and causes electrical overstress (EOS). However it is easy to block propagation of EMI on ground by installing highly-effective ground EMI filters in ground lines. Our unique patented ground EMI filters provide very low impedance for DC and mains' power while effectively blocking propagation of high-frequency currents throughout facility or equipment ground. Ground filters meet safety standards, as well as SEMI E176, ANSI/ESD S6.1 and ANSI/ESD S20.20.
OnFILTER offers ground EMI filters for the facility and for grounding inside the equipment, providing universal protection against propagation of EMI. Select below the category of ground EMI filters of your interest for more details.
Installs in-line with ESD grounding
inside equipment to block EMI
propagation throughout the tool
Any electrical equipment generates unwanted high-frequency voltages and currents in a course of its normal operation. This electrical noise is often called EMI -Electromagnetic Interference. It resides on power lines and ground. Typical frequency spectrum of this type of noise is between ~40kHz and10MHz. High frequency signals propagate quite differently from DC and 50/60Hz low frequencies. A regular grounding wire that provides near-zero resistance for DC, becomes an inductor at high frequencies which together with parasitic capacitance to other metal parts causes resonances. The result is that high-frequency voltage in one location on the tool may be quite different from any other place. Both parts are properly ESD-grounded. Yet, the voltage between them can be magnitudes higher than is specified in the standards. ESD grounding is no guarantee of equipotential situation at high frequencies. The only practical way of assuring equipotential environment on ground at high frequencies is to block propagation of high-frequency currents in the tool. OnFILTER designed special miniature ground EMI filtersGLE04-01 that connect in line with regular ESD grounding.
Grounding in the facility connects all equipment - electrical noise generated by one tool propagates throughout the entire facility. Unlike radiated emission electrical noise on wires (called conducted emission) does not drop off as quickly with the distance and can reach far. The main purpose of grounding is safety, secondary purpose in some facilities (mostly electronic manufacturing) is reduction of ESD risk. Many factories employ both types of grounding - via power line ground and a separate ESD ground. Not discussing merits of this approach, it adds a parallel grounding network and creates ground loops which exacerbate EMI situation. Grounding is a common electrical connection between every piece of equipment in the facility. If any of the tools is electrically noisy it supplies this high-frequency signal to its ground which then propagates to other equipment GLE30-1 present very high impedance for EMI while retaining very low safety-compliant impedance for 50/60Hz mains' power and DC. Properly connected, ground line filters GLE30-1 break the flow of high-frequency signals on ground and confine them only to the noise source providing the rest of the equipment in the facility with clean noise-free grounding.