A Study of Reducing the Residual Stresses for Multilayer Chip Inductors

Abstract

The residual stress built up by sintering causes not only the destruction of the structure of magnetic components but also a reduction in their permeability. In this paper, the relationship between residual stress and permeability is examined, and two possible methods for improving this situation are presented. Because one of the causes of increased residual stress is competition between the shrinking behaviors from the silver and ceramic layers inside the components during sintering, the first method is changing the particle size of the silver paste to alter its shrinking behavior. The results show that choosing a finer silver particle paste as the inner electrode material can reduce the onset temperature of shrinkage of the silver layer and then separate the silver layer from the ceramic layer to shrink the layers individually, reducing the residual stress. The second method is based on the phenomenon of separate shrinking seen in the first method, and we used carbon paste as the isolation layer for the silver and ceramic layers to achieve this. The results show that this method can reduce the residual stress more than the first one, although it can cause a high direct current resistance (DCR) and a low bending strength, and other conditions should be considered in order to avoid these weaknesses.