The Effects of Sintering Temperature Variations on Microstructure Changes of LTCC Substrate

The successful development and commercialization of high performance ceramic materials has attracted much attention especially for multilayer substrates using the Low Temperature Co-fired Ceramic (LTCC) technology. This technology has become a popular technology for automobiles and wireless communications due to the advantages of the excellent combination of electrical, thermal, mechanical and chemical stability for a wide range of applications, thus allowing preparation of 3-dimensional circuits incorporating passive components within a multilayer construction (Matters-Kammerer et al., 2006; Zhou et al., 2008). This approach also allows the presence a number of interfaces and thus reduction of the overall substrate size and cost can be realized (Lo and Duh, 2002; Chen et al., 2004 and Zhu et al., 2007). The circuits are capable of withstanding sintering during processing temperatures up to 1000 °C. For telecommunication applications the usage of ceramic is implemented in Telecom control station and power supply circuits for the capability to dissipate excess heat and maintain dimensional control stability of the ceramic package. This is important where back-up power is required to maintain operation during primary power outages when cooling is restricted (Barlow and Elshabini, 2007). Another important parameter for wireless communication devices is the requirement to have low dielectric loss (tan δ ∼ 10-3 or less) for higher processing speed, higher dielectric constant (ε’>10) for miniaturization of the devices and higher integration density (≥ 3 g/cm3) (Kume et al., 2007; Long et al., 2009). For this reason, it is important to prepare high quality LTCC substrate/package whose properties are strongly dependent on microstructure, phase purity and sintering temperature (Xiang et al., 2002). Therefore the microstructure must be carefully controlled to get dense and fine grained ceramics in order to improve their properties and reliability in many applications (Hsu et al., 2003).