Uni-directional shrinkage sintering technology was studied to fabricate ceramic packaging substrates which meet requirements of very low dimensional tolerances (high dimensional accuracy). Three methods were considered. The first method used laminating of long fiber sheet materials and showed restraining effects on X, Y-directional (plane dimensional) shrinkage. However, the restricting ability was not sufficient for thicker laminates of the green sheets. The second method incorporated short fibers with a planar arrangement in green sheets, and some constraining effects on X, Y-directional shrinkage were observed with increasing short fiber content and modification of the fiber mixing method. But there was concurrent lowering of densification. The third method applied pressure lightly during sintering without using a mold. Control of the sintering shrinkage was relatively easy and X, Y-directional shrinkage of less than 0.1% was achieved by selecting a suitable pressure for the process. This method is very simple and easy to control, ensuring products of high dimensional accuracy.