| 摘要 |
PROBLEM TO BE SOLVED: To impart excellent surface smoothness, a high Young's modulus and a low specific gravity to a glass ceramic substrate by making the glass ceramic substrate have a specified ratio of its Young's modulus to its specific gravity and a specific Al2O3 content. SOLUTION: The high-rigidity glass ceramic substrate is prepared so that it may have the ratio of its Young's modulus (GPa)/its specific gravity of 37-63 and the content of Al2O3 of 10-20 wt.%. This base plate substantially does not include Na2O, K2O, Li2O, PfO and its main crystal phase comprises at least one selected from cordierite or cordierite solid solution, spinel crystals, solid solution of spinel crystal, enstatite, enstatite solid solution,β-quartz andβ-quartz solid solution and the particle sizes of the crystals in individual crystal phases are adjusted to 0.05-0.30μm. Further, this base plate has a thermal expansion coefficient of 30×10-7-50×10-7/ deg.C in the temperature range from -50-+70 deg.C and the surface roughness Ra after polishing of the substrate is 3-9Åand the maximum surface roughness Rmax is <=100Å.
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