Use Case for Suppression of Electrostatic Discharge and Its Effectiveness

In mobile devices such as smartphones, protection devices such as chip varistors are used to prevent malfunction or damage to the circuit due to electrostatic discharge (ESD), but the noise suppression sheet from TDK known as "Flexield" IFL series (abbreviated simply to "Flexield" below) is a product which is also effective in suppression of electrostatic discharge. Use case and its effectiveness are presented below.

Figure 1 is a schematic diagram showing a test example of the application of electrostatic discharge to the wiring of a printed circuit board mounted with a SoC. The strong electrical field and magnetic field produced around the wiring are the causes of noise. 

Flexield has the characteristic of absorbing magnetic noise and converting it into heat. Because of this characteristic, Flexield functions as an absorber of surge noise such as electrostatic discharge.

Figure 1: ESD (Electrostatic discharge) application test example (Schematic diagram)

Electrostatic discharge contains noise components over a wide frequency band

We checked the effectiveness of suppression of electrostatic discharge by Flexield by conducting the ESD test IEC61000-4-2. The discharge waveform used in the ESD test specifies a variety of models using various combinations of energy storage capacity and discharge resistance. The model used to test the damage to devices such as ICs due to electrostatic discharge from the human body is known as the Human Body Model (HBM), and the typical value for electrostatic capacity is specified as 150pF, while the typical value for resistance is specified as 330Ω. The graph in Figure 2 compares the measured waveform in the absence of any measures and when Flexield is used (ESD voltage = 2000V). The peak voltage in the absence of any measures is 1630V, and it becomes 1410V with the use of Flexield, which is a drop of approximately 15% in the peak voltage value. 

The electrostatic discharge waveform which rises sharply in an instant contains noise components over an extremely wide frequency band. The noise suppression sheet from TDK, known as the IFL series "Flexield", is extremely effective in noise suppression over a wide band from a low frequency to a high frequency, and as a result, Flexield is effective in lowering the peak voltage of the electrostatic discharge.

Figure 2: ESD application test and effectiveness of Flexield