Internal stresses in BaTiO3/Ni MLCCs

The internal stresses in BaTiO3 based multilayer ceramic capacitors (MLCCs), showing Y5V characteristics, were estimated with a sharp indentation method using a micro-indenter. The influence of the direction to electrode on the internal stresses, especially residual stresses, was investigated at the three planes (x, y, and z planes), including the effect of the distance from the electrode on hardness. Hardness is constant to a special distance from the electrode, depending on the plane, and modestly decreases above that distance. The internal stresses at the planes parallel to the electrode, x and y planes, indicate the compressive and tensile stresses in the directions parallel (x and y directions at x and y planes, respectively) and perpendicular (z direction) to the electrode, respectively. The internal stresses at the plane perpendicular to the electrode, z plane, are compressive in both directions. The extrinsic stress induced by the fabrication process is tensile, which is much severer than the intrinsic stress by the material constants. The internal stresses created on MLCCs are dependent on the plane with the lamination and the direction to the electrode, parallel and perpendicular directions. Crack formation and damage mode related to the internal stresses are also discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.