Influence of the charging effect on HBM ESD device testing

The standards for testing the ESD sensitivity of electronic components according to the HBM (MIL, JEDEC, ESDA) require a specific switch in the HBM ESD waveform generator to ensure that the socket and the DUT is not left in a charged state after the stress. The absence of this switch may result in the wrong ESD threshold levels. For two different waveform generators, the charging effect was measured by using an electrostatic voltmeter. An unexpected experimental result, showing that the HBM ESD threshold voltage strongly depends on the number of stress pulses, could be explained by the measured charging of these components. Consequences for other types of components and corrective actions are discussed.