New mullite ceramic packages and substrates

The authors describe the fabrication technologies and properties of new mullites for advanced VLSI packaging technology, as well as applications utilizing their characteristics. These new mullite ceramic substrates have the following characteristics: (1) low dielectric constants (5.4-7.5), which facilitate the realization of a device manifesting a high speed of signal transmission; (2) low thermal expansion coefficients (3.0-4.05*10/sup -6// degrees C), which permit the direct attachment of a large silicon chip; and (3) sufficiently high flexural strength (20-31 kg/mm/sup 2/), providing high mechanical reliability for practical use. It is concluded that, as a result of these characteristics, the new mullite packages and substrates could guarantee a highly reliable attachment for a large silicon chip and high signal transmission speed.<>