Miscorrelation between IEC61000-4-2 type of HMM tester and 50 Ω HMM tester

Several ESD protection devices are evaluated on-wafer with an IEC61000-4-2 type of HMM tester and a 50 Ω HMM tester. No clear correlation between the two tester models has been obtained. The 50 Ω source impedance triggers different failure modes and even different failure causes.