A study of “soft grounding” of tools for ESD/EOS/EMI control

The effect of a discrete resistor placed in the ground wire connected to a metal tool block or hand tool on ESD/EOS/EMI control is studied. Experimental results and SPICE circuit simulations show that in most cases "soft grounding" results in no reduction in CDM current, noise voltage or radiated fields (EMI) because of capacitive coupling. However, using a high-resistance, static dissipative material at the interface between the device input and metal tool was extremely effective in reducing the voltage and current associated with ESD/EOS/EMI and increased the CDM failure level of a Class 0 ESD sensitive device from 5 V to over 200 V.