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The sintering and properties of cordierite–borosilicate glass composites were investigated. For the composites with 艌35% low-viscosity glass, the sintered densities decreased with the increasing sintering temperature above 850 °C. No crystallization of the glass was found. For the composites with 50–90 wt% high-viscosity glass, the sintered densities remained nearly constant (>95%) in a wide sintering temperature range. However, cristobalite crystallized from the glass phase, resulting in an undesirably high coefficient of thermal expansion. Presintering processing and a lower heating rate improved the densification of the composites with low-viscosity glass while limiting that of the composites with high-viscosity glass. This result is explained by the difference in crystallizability between these two glasses. As low- and high-viscosity glass powders were simultaneously added, the density reduction was reduced and the coefficient of thermal expansion was closer to that of Si because of the absence of cristobalite phase. The dielectric constant of all the composites was in the typical range of 4.9–5.7 at 1 MHz.
I. INTRODUCTION
Several efforts have been made for developing multilayer ceramic substrates to replace conventional alumina substrates for high performance large-scale integrated (LSI) packaging.1 To fulfill the high-speed signalpropagation requirement, the substrate material should have a low dielectric constant. Further, to avoid damage to the semiconductor due to thermal stress, the thermal expansion coefficient of the substrate material should be near that of Si (3.0 × 10−6 K−1). In addition, a low sintering temperature (
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