Xiaojin Tang

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.

3-Dimensional Characteristic of Electric Field and Potential Induced by Internal Charging Effects in Typical PCB

To assess satellite internal charging effects more accurately, a 3-D computation method is developed to study the internal charging problems with realistic geometry and grounding configuration. The method includes two steps: 3-D electron transport simulation and internal electric field computation. The transport simulation is carried out by a self-developed software based on GEANT4. And 3-D internal electric field is calculated through solving a set of electrostatic equations by COMSOL Multiphysics. In this work, the 3-D characteristics of electric field and potential in a typical PCB irradiated by an electron beam through an aluminum shield are demonstrated. This PCB is partially grounded by a rectangular circuit and the electron beam uses the GEO space-like spectrum with flux in the worst case. According to these conditions, the 3-D field and potential distributions in charging stationary state can be computed. Finally, the following conclusions are drawn: distributions of dose and charge deposition rate have remarkable edge effects. Severe distortion of electric field can arise around edges of partial grounding, especially at corners. The degree of field distortion decreases significantly with the increase of the distance from the grounding surface.

A 3-dimensional model of internal charging simulation

To break through the limitation of the traditional 1-dimensional (1-D) method of internal charging computation, a 3-D calculation model of internal electric field and potential for arbitrary configuration dielectric with complex boundary conditions is developed. It includes two steps: 3-D electron transport simulation and internal electric field computation. The transport simulation, which aims for obtaining electron deposition and dose rate distribution, is implemented by a self-developed software founded on GEANT4. And the calculation of 3-D internal electric field, which takes above transport results as input, is conducted through solving a set of electrostatic equations by the software COMSOL Multiphysics. In this paper, this 3-D simulation model applied to a typical printed circuit board grounded on a rectangular circuit and cylindrical pin will be presented. For purpose of comparison, a simpler 1-D planar dielectric wholly grounded on the back surface is simulated in the same method. Finally, 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. Besides, the following conclusions are drawn: grounding has significant influence on electric field distribution, and the maximum field generally occurs at grounding edges or corners. Increasing the curvature radius of the circuit corner can reduce the field and the discharge risk.