Why can static electricity break down the MOS tube? how to respond?

The MOS tube is an ESD sensitive device with high input resistance and very small capacitance between the gate and the source, so it is easily charged by the induction of external electromagnetic fields or static electricity, and it is difficult to discharge the charge in the case of strong static electricity. Cause electrostatic breakdown.

There are two ways of electrostatic breakdown:

Voltage type: the thin oxide layer of the gate is broken down to form a pinhole, which short-circuits the gate and the source, or short-circuits the gate and the drain;

Power type: that is, the metalized film aluminum strip is blown, resulting in an open gate or an open source.

The basic physical characteristics of static electricity are:

1. Have the power to attract or repel;

2. There is an electric field, and there is a potential difference with the earth;

3. Will produce discharge current.

These three situations, namely ESD, will generally affect the following three situations on the MOS tube:

1) The component absorbs dust, changes the impedance between the lines, and affects the function and life of the component;

2) Due to the electric field or current destroying the insulation layer and conductor of the component, the component cannot work (complete destruction);

3) Due to the instantaneous electric field soft breakdown or the overheating of the current, the component is injured. Although it can still work, the service life is impaired.

Therefore, the damage of ESD to the MOS tube may be one or three cases, and it is not necessarily the second case every time.

In the above three cases, if the component is completely destroyed, it can be detected and eliminated during production and quality testing, with less impact.

If the component is slightly damaged, it is not easy to be found in the normal test. In this case, the damage is often found only when it has been processed many times or even when it is in use. Not only is it difficult to check, but the loss is also difficult to predict. The damage caused by static electricity to electronic components is no less than the damage caused by serious fire and explosion accidents.

Under what circumstances will MOS tubes and products suffer electrostatic damage?

It can be said that the whole process of electronic products from production to use is threatened by static electricity. From device manufacturing to plug-in assembly and welding, complete machine assembly, packaging and transportation to product application, all are under the threat of static electricity.

In the entire production process of electronic products, at every small step in each stage, electrostatic sensitive components may be affected or damaged by static electricity. In fact, the main and easily neglected point is the transmission and transportation of the components. process.

In this process, transportation is damaged due to static electricity generated by the movement easily exposed to external electric fields (such as passing near high-voltage equipment, frequent movement of workers, rapid movement of vehicles, etc.), so special attention should be paid to the transmission and transportation process to reduce losses and avoid indifference Disputes.