Static problem solving method

Issue Time:2019-05-15
To solve the ESD problem, you need to classify the devices to handle different types of devices:

A type of equipment: metal structure equipment, metal casing connected to the earth. Including two situations:

One is to connect to the earth through the system ground wire, and the other is to connect to the earth through the PE wire in the power supply.

The second type of equipment: metal structure equipment, the outer casing is not connected to the earth. Such as MP3 players.

Three types of equipment: plastic structural equipment.

One type of equipment electrostatic problem handling

The principle of solving such EsD problems: rapid discharge of static current, the electrostatic test of such equipment is mainly for the outer casing of the equipment, the outer casing of the connector, the indicator light, the reset button, the dial switch, the power switch, etc., so These areas should be treated when static problems occur.

Current path determination for case discharge problem

Determine the electrostatic discharge path by laying the outer casing of the device and drawing a straight line along the discharge point to the grounding point of the device. Generally speaking, this straight line is the way to discharge static electricity.

Check if there is a structural hole in one of the paths that is “unobstructed”, causing the field generated by static electricity to radiate through the hole to the inside of the device.

Solution: Use copper foil, aluminum foil or conductive cloth to "electrically block" the hole seam for comparison test.

Check if this path is "clear"

If the discharge point and the grounding point are in different structural parts of the device (ie, the two points are not on a complete metal body), check whether the electrical overlap between the two metal parts is good. Generally, attention needs to be paid. Whether the lap joint is in contact with a large area, no spray varnish is sprayed.

Is there an internal cable near the bleed path?

Whether there is a device internal wiring near the electrostatic current discharge path, especially when there is a structural gap on the discharge path, there is a signal line near the gap.

Solution: Change the wiring of this cable, away from the hole in the discharge path or discharge path; add a magnetic ring on the signal line to cut off the common-mode current of the static induction.

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