Theory of pressure sintering of glass ceramic multichip carriers

A method of pressure sintering multilayer glass ceramic packages (MLC) that results in a hermetic product is described. Use of this process results in a reduced process time, and is achieved without the use of a die, which is commonly employed during pressure sintering. Complex glass ceramic multichip substrates have been sintered this way to produce products with a flat edge contour and minimal distortion of the internal vias. In this article, we present a model that provides the fundamental basis for the pressure sintering approach to processing MLC. In this semi-quantitative model, the mechanism of pressure sintering, i.e., the process of dimensional changes, is controlled by viscous flow induced by sintering, and lamination flow created by an applied pressure. The pressure sintering model is capable of predicting the flow, density, and dimensional changes of a glass ceramic carrier during pressure sintering in the absence of a die. Both the temperature and pressure schedules are time dependent, and the pressure can vary over a range from zero, corresponding to free sintering, to large pressures (up to at least 800 psi) that closely simulate experimental data.