【正文】 Dielectric strength: not less than Dielectric loss factor: not larger than Property Target for Ceramic Substrates Low dielectric constant: e7 Low dielectric loss: tand4x104 High resistivity: ?~ High thermal conductivity。CaOAl2O3) 95 103 1710 Fair Mullite (3Al2O3SiO2) 100 125 650 Moderate Forsterite (2MgOSiO2) 1012 Quartz (SiO2) 101418 PbAl silicate 1013 Aluminum Nitride (AlN) 15 1013 Silicon — — — — Table Thermomechanical Properties of Ceramic Insulators Material Specific gravity Thermal conductivity at 25oC (cal/secoCcm) Thermal coefficient of expansion 25300oC (106/oC) Tensile strength (Mpa) MOR Transv strength (Mpa) Compress strength (Mpa) Thernal shock resistance Porcelain (R2Ocm) Thoria (ThO2) ~ 1010 Hafnia (HfO2) 12 — 108 Ceria (CeO2) 15 — 109 Spodumene (Li2O2Al2O3SiO2) 1014 Zircon (ZrO2 Dielectric loss (dissipation factor): not larger than 。 Thermal expansion coefficient。 Ancillary but important other functions are to provide mechanical support, heat dissipation and environmental protection for the conductors Advantages of ceramic insulators: …… Materials type used as insulators: linear dielectrics Typical elements of ceramic insulator: ceramic substrates, ceramic packages Property Requirements to Ceramic Insulators Dielectric constant。 A large range of relaxation times can indicate multiple polarization mechanisms but also losses due to conduction. A perfect or low loss dielectric would have a ColeCole plot that is nearly a semicircle。1 ee?= rC])(1)[( 222039。39。1 tweeee??= ?? rrsrr2239。*2239。 Debye Equations Equation () can be integrated to give () By neglecting the transient Cexp(t/t), we can get () The Debye Equations are obtained by separating the real and imaginary parts of Eq. () () () The relaxation frequency is w=1/t *039。wgwwwwee ??=? mNer})({ 22222002wgwwgwee ?=? mNerVariation in and with frequency close to a resonance frequency w0. 139。 sP – polarazation charge density Since P= sP and sT=D (electric displacement) e0 E=PD () D= e0 E+ P () If the dielectric is linear, P=ce e0 E, so that D= e0 E+ ce e0 E=(1+ ce) e0 E () where, ce is electric susceptibility, a tensor of the second rank 介電常數(shù) (Dielectric Constant) Since D= sT, QT/A= (1+ ce) e0 U/h () QT =(1+ ce) e0 UA/h () C=QT/U= (1+ ce) e0 A/h () Since vacuum has zero susceptibility, C0=e0 A/h () If the space between the plates is filled with a dielectric of susceptibility ce, the capacitance is increased by a factor 1+ ce. Permittivity e of the dielectric is defined by e =e0(1+ ce) () Dielectric constant (relative permittivity) er = e /e0=1+ ce () An individual atom or ion in a dielectric is not subjected directly to an applied field but to a local field. The internal macroscopic field E