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|Structure and Application of Al(2)O(3)-Glass-Based Self-Constrained LTCC|
|Keywords: LTCC, Constrained sintering, Al2O3|
|LTCC (Low Temperature Co-fired Ceramics) substrates and packages have established themselves as a leading technology for integrated passive devices with low loss conductive circuit. Though free sintered LTCC system is cost effective, the dimension of the final fired circuits should be hard to predict for circuit design and the dimensional tolerance is higher. Constrained sintering approach greatly reduces the overall X- and Y- shrinkages of green ceramic laminates and dimensional tolerance of the shrinkage could be recovered. Three main process technologies for constrained sintering, self-constrained, pressure-assisted constrained, and pressure-less constrained sintering, are suitable for industrial application. This paper describes a design of the self-constrained LTCC system. Self-constrained technology has advantage in the simple process, high strength substrate and package with complicated structures among the constrained sintering approaches. Self-constraining layer contained Al2O3 powder and glass element of usual glass-Al2O3 LTCC layers were Ca-Al-Si-Mg-B-O for our system design. Inner Al2O3 self-constraining layers were unified into the substrate by the glass penetration through the firing treatment. The effects of various factors of Al2O3 particle self-constraining layer on the properties of substrates were discussed. The relationship between particle size and shrinkage rate was clarified. To secure high strength substrate, the influence of the thickness for Al2O3 self-constraining layer on the bending strength was noteworthy to be investigated as a fundamental research. Inner constraining layer sustained strength of the substrate and it was appropriate technology to have cavity structure. Inner self-constraining layer contributed to avoid the defects as cracking or deformation the cavity area. Thin package with 150mm thickness and cavity, was shown as our application example of this unique technology.|
|Takahiro Takada, Section Manager
Murata Manufacturing Co., Ltd.