How to judge the damage of the electrostatic diode

How to judge the damage of the electrostatic diode

ESD diodes are a critical protective element used to prevent damage to electronic devices caused by electrostatic discharge (ESD). It plays an important role in semiconductor devices, especially in sensitive integrated circuits. However, although ESD diodes are designed to resist short-term high-voltage shocks, in some cases, they can be damaged

How electrostatic diodes work

The main function of an electrostatic diode is to direct an excessively high voltage to ground, thus protecting the circuit from electrostatic discharge. When the voltage exceeds its breakdown voltage, the ESD diode quickly turns on, allowing the overvoltage to bleed through the diode to ground, preventing damage to sensitive circuit components. When the voltage returns to a safe level, the diode returns to a high-impedance state.

Causes of electrostatic diode damage

Damage to electrostatic diodes is usually caused by several reasons:

Excessive electrostatic discharge: If the energy of the electrostatic discharge exceeds the capacity of the diode, it can cause the diode to overheat and be permanently damaged. This damage is usually caused by the frequent occurrence of electrostatic events or a severe electrostatic shock.

Overvoltage or overcurrent: Although electrostatic diodes are designed to withstand transient high voltages, if they are exposed to overvoltage or overcurrent for a long time, it may cause their breakdown voltage to drop or their internal structure to be damaged, and eventually lose their protective function.

Environmental factors: Environmental factors such as high temperatures, humidity, and corrosive gases can also cause aging and damage to ESD diodes. These factors can accelerate the deterioration of the material, causing the diode to gradually degrade until it fails.

Symptoms of electrostatic diode damage

When an electrostatic diode is damaged, the following symptoms may occur:

Unstable circuits: If a circuit exhibits instability after being subjected to a minor electrostatic shock, or if there is a sudden unexplained fault, this can be a sign of ESD diode failure. At this point, other sensitive components may be exposed to an unprotected state.

Abnormal resistance: Normally, ESD diodes exhibit high impedance when reverse biased. When a diode is damaged, it may manifest as a low impedance (short circuit) or an open circuit. When measuring with a multimeter, if the reverse resistance is found to be close to zero, the diode may be short-circuited; If the resistance is infinite, it may indicate open circuit damage.

Physical damage: Although uncommon, severe electrostatic shocks can cause damage to the diode's appearance, such as cracks, burning, or discoloration. This condition is usually accompanied by a complete failure of the diode.

How to test electrostatic diodes

In order to accurately determine whether an electrostatic diode is damaged, the following test methods can be used:

Forward and Reverse Resistance Test: Use a multimeter to test the forward and reverse resistance of the diode. Under normal circumstances, the forward resistance is small, and the reverse resistance should be very large. If the reverse resistance is abnormally low, the diode may be short-circuited; If both forward and reverse resistance are abnormally high, the diode may be open.

Clamping Voltage Testing: Observing whether an ESD diode can effectively clamp the voltage by simulating electrostatic events in the circuit. A transient voltage is applied to the diode and the clamping voltage is observed to see if it is within the normal range. If the clamping voltage fails, the diode may be damaged.

Curve Trace Test: The V-I characteristic curve of an ESD diode can be visualized using a curve tracker. A normal diode should exhibit a sharp current rise when the breakdown voltage is exceeded. If the curve is not normal, such as turning on at low voltages, or not turning on at high voltages, the diode may be damaged.