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Why can static electricity break through the MOS tube?After reading this article to teach you how to deal with it easily!

In fact, an ESD sensitive device is tube. Its input resistance of itself is very high, and the barricine-Yuanji capacitor is very small, so it is very easy to be charged by the inductive induction of the external electromagnetic field or static electricity.Putting charge is easy to cause static breakdown.

There are two ways to static breakdown:

The first is the voltage type, that is, the thin oxidation layer of the gate occurs, forming a pinhole to make the gate and the source short circuit, or make the grid and the drain short circuit;

The second is the power type, that is, the metallic film aluminum strip is fused, causing the gate to open the road or the source opening.

The basic physical characteristics of static electricity are:

1) There is a power to attract or exclude;

2) There is an electric field, which has a potential difference with the earth;

3) The discharge current will be generated.

These three situations, that is, ESD generally affect the following three situations on electronic components:

Influence

1) Component adsorption dust, change the impedance between the line, and affect the function and life of the component;

2) Due to electric field or current damage component insulation layer and conductor, the component cannot work (completely damaged);

3) Due to the soft breakdown or current of the instantaneous electric field, the element is injured. Although it can still work, the life span is damaged.

Therefore, the damage of ESD to MOS pipes may be one, three or two, and not necessarily the second case every time.

In these three cases above, if the component is completely damaged, it will be eliminated in production and quality testing, with less impact.

If the component is slightly damaged, it is not easy to be found in normal testing. In this case, it will often be found to be destroyed due to multiple processing and even use it. Not only is it difficult to check, but the loss is difficult to predict.The harm of static electricity to electronic components is no less than the loss of severe fire and explosion accidents.

Under what circumstances will electronic components and products be damaged by static electricity?

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

During the production process of the entire electronic product, every small step in each stage, static sensitive components may be affected or damaged by static electricity. In fact, the most important and easily negligent point is that in the transmission and transportation of componentsthe process of.

In this process, transportation is easily damaged by electrical electricity (such as nearly high -voltage equipment, frequent mobility of workers, and rapid vehicle movement, etc.).Disputes.In the case of protection, Gazina's voltage stabilization tube protection.

The current MOS tube is not so easy to break, especially the high -power VMOS, mainly because many of them have diode protection.

VMOS gate capacitance is large, and the induction does not have high voltage.Unlike the dry north, the dampness of the south is not easy to generate static electricity.There is now that most CMOS devices have added IO port protection inside.However, it is not a good habit to directly contact the CMOS device to tube feet.At least the weldability of the tube feet is worse.

The reasons and solutions of the MOS tube's breakdown

First, the input resistance of the MOS tube itself is very high, and the pole capacitance of the gate is very small, so it is very vulnerable to the induction of the external electromagnetic field or electrostatic induction, and a small amount of charge can form a quite high voltage on the polar capacitor.(U = q/c) damage the tube.

Although the MOS input terminal has anti -static protection measures, it is still necessary to treat it carefully. It is best to pack it with metal containers or conductive materials in storage and transportation. Do not place it in chemical materials or chemical fiber fabrics that are prone to electrostatic high -voltage.

During assembly and debugging, the tools, instruments, and workbenchs should be well grounded.To prevent damage caused by electrostatic interference of operators, if you should not wear nylon and chemical fiber clothes, it is best to connect the hand or tool before the contact set.When the device lead is straight or artificially welded, the equipment used must be well grounded.

Second, the protection diode of the MOS circuit input terminal is generally 1mA. When a large transient input current (exceeding 10mA) may occur, the input protection resistance shall be connected in series.The protection resistance is not added during the initial design, so this is why the MOS pipe may be penetrated, and the MOS tube with a protective resistance inside should prevent this failure.

In addition, due to the limited energy of the protection circuit's absorption, too large momentum signals and excessive electrostatic voltage will lose the protective circuit.Therefore, when welding, the electric soldering iron must be reliable to prevent the input terminal of the leakage of the electrical breakdown device. Generally, it can be used for welding after power off.

MOS is a voltage drive element, which is very sensitive to voltage. The suspended G is easy to accept external interference to drive MOS. The external interference signal is charged to the G-S knot capacitor. This tiny charge can be stored for a long time.

In the experiment, G hanging is very dangerous. Many of them are because of such explosive tube. G connected to the pull -down resistance to the ground.

This resistance is called a gate resistance, which is function 1: provides offset voltage for field effect tube; function 2: play the role of laxative resistance (protecting the gate G ~ source polar S).

The first role is easy to understand.Here is the principle of the second role: protecting the G-S pole of the field effect tube of the G-S pole that protects the G-S of the G-S: so as long as a small amount of electrostaticEnd of the effect capacity generate high voltage.

If these small amounts of electrostatic diarrhea are not released in time, the high voltage at both ends may cause misunderstanding of the field effect tube, or even break through its G-S pole; at this timeThe above -mentioned static diarrhea is released, which plays a role in protecting the field effect tube.