Internal Electrostatic Discharge Modelling: Validation and Fitting using Test Data on Insulated Wires

The goal of the task documented in this paper is to improve the state of the art of modeling of internal electrostatic discharge (IESD). Typical approaches to IESD modeling involve five basic steps: 1) establishing the expected radiation environment, 2) calculating how the radiation environment deposits charge and energy within the components of interest, 3) simulating how the deposited charge migrates within the material to establish electric fields and the point of dielectric breakdown, 4) determining how the stored charge and energy is released, and 5) determining how the resulting arc event propagates to and presents on interfaced circuit components. The quality of step 1 depends on the environment: some environments are known quite well and others are not. Step 2 has been worked out fairly well for quite a few years; charge and energy deposition rates can be determined with good accuracy by existing radiation transport codes, such as TIGER and MCNP. Step 3 has also been worked out quite well, though only recently with tools such as 1D NUMIT and 3D NUMIT. Step 3 does suffer from extreme sensitivity to difficult-to-ascertain material properties, such as dark conductivity, radiation induced conductivity, relative permittivity, and breakdown inception field. Most often, steps 4 and 5 are condensed to a simple fit to one or another electrostatic discharge (ESD) test standard (e.g., Human Body Model, Machine Model, etc.), constraining the model parameters based on convenience rather than on physics simulation or test data. This paper presents simulation and test results that show that using a more tailored arc model based on the charging simulation and impedance of the arc source and connected circuits can replicate observed arcs quite well. The example case of IESD events from insulated wires is explored in some depth.