Novel Glass-free LTCC Material co-fired with Cupper-Electrodes

Abstract

Low Temperature Co-fired Ceramics (LTCC) have excellent high-frequency characteristics and have widely been used for microwave electronic components. By lowering the sintering temperature of the ceramics used as insulating layers, LTCC was co-fired with a high-conductivity wiring conductor, such as Cu or Ag. LTCC substrate has been expected as one of the most promising technologies to realize miniaturization of RF circuits in the field of wireless communications. There is no limitation to demand for further downsizing of RF circuits, suppression of electric loss and high mechanical strength of the substrate. However, conventional LTCC materials for substrates contain glass frit which causes defects, such as pores or cracks, and low mechanical strength. In this work, we have developed a novel LTCC material system BaO-Al2O3-SiO2-MnO-TiO2, without any glass frits. The material was co-fired with cupper electrodes, which have low resistivity and show less diffusion than silver in LTCC, under a low-oxygen partial pressure atmosphere (mixture of N2 and H2) at 980°C. Thin layers (8μm) of the material showed high insulating resistivity and reliability due to few defects, such as pores, in LTCC. Its dielectric and mechanical properties were measured as 6.8 (low-εr), 350 at 3GHz (high-Q-value) and 341MPa (high mechanical strength) respectively. This LTCC material will contribute to further miniaturizing of microwave applications and integration of passive elements.

Ultralow-Permittivity and Temperature-Stable Ba1–xCaxMg2Al6Si9O30 Dielectric Ceramics for C-Band Patch Antenna Applications

“…As shown in Figure e, the Ba 1– x Ca x Mg 2 Al 6 Si 9 O 30 ( x = 0.1) ceramic without the obvious peaks of thermal expansion exhibited the lowest average CTE (2.668 ppm/°C) at −150 °C ≤ T ≤ 850 °C and near-zero CTE (1.254 ppm/°C) at −150 °C ≤ T ≤ 260 °C. It is clear from Figure f that the Ba 1– x Ca x Mg 2 Al 6 Si 9 O 30 ( x = 0.1) ceramic could achieve properties comparable to those of reported materials, − and the ultralow ε r at microwave and terahertz ranges and low CTE over the ultrawide temperature range were obtained in the Ba 1– x Ca x Mg 2 Al 6 Si 9 O 30 ( x = 0.1) ceramic.…”

Low-temperature co fired ceramic materials with three different dielectric constants

“…[10][11][12][13] Capacitors, inductors, resistors, and other electronic components compose the multilayer circuit, enabling the downsizing and enhancement of their properties. [14][15][16][17] Co firing two materials, in which one has a high dielectric constant for capacitors and the other has a low dielectric constant for inductors, leads to further downsizing and enhancement. [18][19][20] When co firing materials of different dielectric constants, the inter diffusion at the boundary of each material causes the deterioration of electronic properties, and the difference in the coefficient of thermal expansion (CTE) generates mechanical defects in the co fired body.…”

Mechanical strength of low-temperature co-fired ceramic multi-layered substrate

“…This technique enables substrates to be downsized by containing passive functions in the substrates. 12) 19) Recently, low-profile substrates have become more important due to the demand for the miniaturization of electronic components. However, LTCC substrates are becoming thin, so they easily break during the manufacturing process or actual usage.…”