esd tester is actually an electrostatic discharge generator. static electricity is caused by the mutual friction of two different substances, and high voltage is formed by the accumulation of positive and negative charges in two objects that rub each other. man made fibers and plastics are common friction electrification materials. when friction generates voltage, esd problems will occur. for electronic components, electrostatic energy can not be ignored. it can puncture semiconductor components and destroy electronic circuits.
generally, esd testers generate emc problems in two main ways: conduction and radiation interference.
(1) conduction mode. electrostatic discharge current flows directly through the circuit, because esd generates a high voltage. if it enters the semiconductor, misoperation may occur, and it is easy to damage the semiconductor devices. the internal insulation of modern semiconductor components often breaks down under dozens of volts and is permanently short circuited. this is a very serious esd problem, which is common in daily life.
(2) radiated interference. in case of electrostatic discharge (simulated test with electrostatic discharge tester), the generated spark voltage will generate radiated magnetic field and electric field. the magnetic field can induce noise voltage in each signal loop of the nearby circuit. due to the large electrostatic current generated in a very short time, the noise voltage generated in the signal loop may exceed the threshold level of logic components, causing false triggering of components.
in the circuit, the esd problem caused by human static electricity is the most common. in dry climate, human esd voltage is easy to exceed 8kv, 15kv or even 20kv, so we need to pay attention to the impact of such electrostatic voltage on pcb and components, and take corresponding measures to prevent esd problems.