Low-Permittivity and Low-Temperature Cofired BaSO₄–BaF₂ Microwave Dielectric Ceramics for High-Reliability Packaged Electronics

Abstract

In developing low-temperature cofired ceramic (LTCC) technology for high-density packaging or advanced packaged electronics, matching the coefficient of thermal expansion (CTE) among the packaged components is a critical challenge to improve reliability. The CTEs of solders and organic laminates are usually larger than 16.0 ppm of °C1–, while most low-permittivity (εr) dielectric ceramics have CTEs of less than 10.0 ppm °C1–. Therefore, a good CTE match between organic laminates and dielectric ceramics is required for further LTCC applications. In this paper, we propose a high-CTE BaSO4–BaF2 LTCC as a potential solution for high-reliability packaged electronics. The BaSO4–BaF2 ceramics have the advantages of a wide low-temperature sintering range (650–850 °C), low loss, temperature stability, and Ag compatibility, ensuring excellent performance in LTCC technology. The 95 wt %BaSO4–5 wt %BaF2 ceramic has a εr of 9.1, a Q × f of 40,100 GHz @11.03 GHz (Q = 1/tan δ), a temperature coefficient of the resonant frequency of −11.2 ppm °C1–, a CTE of +21.8 ppm °C1–, and a thermal conductivity of 1.3 W mK–1 when sintered at 750 °C. Furthermore, a dielectric resonant antenna using BaSO4–BaF2 ceramics, a typically packaged component of LTCC and laminate, was designed and used to verify the excellent performance by a gain of 6.0 dBi at a central frequency of 8.97 GHz and a high radiation efficiency of 90% over a bandwidth of 760 MHz. Good match and low thermal stress were found in the packaged components of BaSO4–BaF2 ceramics, organic laminates, and Sn-based solders by finite element analysis, proving the potential of this LTCC for high-reliability packaged electronics.

Millimeter Wave Dielectric Resonator Antenna Using High Quality Factor Temperature Stable Dielectric Ceramic Composite K18 for 5G Applications

“…The analysis of the MT-CLTA sample infrared reflectance spectrum is performed by a classical three parameter resonator harmonic oscillator model using eq . .25ex2ex ε * − ε ( ∞ ) = ∑ j = 1 n false( z j e false) 2 / m j V j ε 0 ω normalT j 2 − ω 2 − j γ j ω infix= ε ( ∞ ) + ∑ j = 1 n ω P j 2 ω normalT j 2 − ω 2 − j γ j ω where ε ∞ is the optical permittivity of ceramic, ω P j is the plasma frequency, ω o j is the transverse frequency, ω T j is the angular frequency of the transverse optical modes, and n is the number of transverse phonon modes, γ j represents defective phonon scattering of j th Lorentz oscillator, V j represents the unit volume of j th vibrational mode, m j denotes the converted mass of positive and negative ions, z j is charge number of j th mode, e represents the elementary charge, whereas normalΔ ε j = S j ω o j 2 , in which Δε j is j th oscillator contribution to permittivity and S j is j th oscillator strength, which can be approximated as contribution to static permittivity …”

“…in which Δε j is jth oscillator contribution to permittivity and S j is jth oscillator strength, which can be approximated as contribution to static permittivity. 38 Complex reflectance [R(ω)] gained by infrared spectra and complex permittivity [ε*(ω)] can be related by eq 3. 39 R( )…”

Ni–Co Complex Ionic Synergistically Modifying Octahedron Lattice of Cordierite Ceramics for the Application of 5G Microwave–Millimeter-wave Antennas

“…A lower dielectric constant (ε r ) reduces the signal coupling loss and improves the signal transmission speed at high frequencies. Hence, advancements in microwave dielectric ceramics are crucial for enhancing the application and user experience of 5G/6G technology in mobile communications, smart driving, healthcare, and other fields. − …”