Improvement of Dielectric Strength of Creepage Surface on Multi-layer Printed Circuit Board

In this paper, discharge characteristics of the creepage surface on multi-layer printed circuit boards are investigated to identify the location where discharge occurs. Arc discharge is initiated by the corner of the surface layer electrode in spite of larger distance to the opposite electrode as compared with the electrode edge with straight line. This is attributed to the fact that electric field concentration originated from the decrease in curvature radius of the electrode edge is dominant rather than the increase in the distance between the electrodes at the corner of the electrode. In addition, novel insulation structures in which electric field intensity is reduced with the layout modification of surface and inner layer electrodes are proposed, which is specific to multi-layer printed circuit boards. The proposed structures enable high dielectric strength without increasing creepage distance.