FAITH MOROCO MOBILE SUPPER

Hybrid microelectronic assemblies for mobile phones as well as other applications in wireless communication have to meet growing demands for functionality and miniaturisation. The electrical performance of the assembly is largely determined by the geometries and materials used in the package and thus, by the technology employed. In wireless communication, low temperature co-fired ceramics (LTCC)-multilayers are one of the most promising packaging concepts. Here, ceramic tapes sinter lower than 950 C and provide fine line wiring by use of high conductivity metals as well as integration of passive components. The realisation of miniaturised buried microwave filters in LTCC substrates requires inner layers with moderate permittivity (30-100), low dielectric loss (tan delta < 0.002) and temperature coefficient of dielectric constant near to zero. To realise such materials, crystalline substances possessing a dielectric constant of about 100 and low dielectric loss, e.g., rutile or Ba(La,Nd)2Ti4O12, were combined with special high permittivity glasses from the systems BaO-Al2O3-B2O3-SiO2 (dielectric constant up to 15) and La2O3-B2O3-TiO2 (dielectric constant up to 20). Glass/crystal phase composites showing microwave properties and sintering temperature below 900 C have recently been developed. 9 refs.

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