a charged device model electrostatic discharge testing is carried out at wafer level . wafer cdm pulses are repeatedly applied and monitored . the wafer cdm pulses are accomplished with a probe - mounted printed - circuit board and a high - frequency transformer that captures fast cdm pulses . modeling of cdm and wcdm in the time and frequency domain illustrates the dominant effects , and shows that wcdm can reproduce all the major phenomena of package - level cdm testing .