3-D Internal Charging Simulation on Typical Printed Circuit Board

To obtain more accurate results of internal charging effects, a 3-D computation method of internal charging electric field and potential for arbitrary configuration is developed. In this paper, the charging of a typical printed circuit board partially grounded, which is immersed in high energetic electrons, is simulated to illustrate the 3-D method. It includes two steps: 3-D electron transport simulation and internal electric field calculation. The electron transport is simulated using a self-developed software found on GEANT4. The 3-D calculation of internal electric field at charging equilibrium is conducted by solving a set of electrostatic equations by the software COMSOL Multiphysics. On the basis of the above-said method, the 3-D field and potential distributions within the board are obtained. For the purpose of comparison, a simpler 1-D planar dielectric grounded at the back surface is simulated in the same method. From the simulation results, the following conclusions are drawn: grounding has significant influence on electric field distribution, and the maximum field generally occurs at grounding edges or corners. The electric field computed by the 3-D algorithm is much larger than the 1-D simplified method widely used at present and, hence, the 1-D method may neglect crucial risk.