Sevgi ŞENGÜL, BSc. Student
Metallurgical and Materials Engineering
Yıldız Technical University
Development of Borosilicate/Al2O3 Glass Composites for LTCC Applications
Co-Supervisor: Ufuk Akkaşoğlu
Low temperature co-fired ceramics (LTCC) are widely used in microelectronic devices as well as electronic packaging and wireless technologies such as radars and antennas [1,2]. LTCCs are ceramics co-fired with a metal electrode. Therefore, the sintering temperature must be lower than the melting point of the electrode (<900 C°) and the metal electrode must be chemically compatible with ceramic [3,4]. Other important characteristics of LTCC materials are low relative permittivity, low dielectric constant to reduce the signal propagation delay, high quality factor (low dielectric loss) to achieve high transmission speed, good thermal conductivity, low coefficient of thermal expansion (adapted to silicon and GaAs), nearly zero temperature coefficient of resonant frequency for frequency stability (especially for 5G applications since the frequency is higher than > 40 GHz), perfect for multilayer processing and integration of passive elements, very resistive against mechanical and thermal stress (hermetically sealed) [3,5]. LTCC is manufactured through two successive stages. The first stage is the production of glass-ceramic sample required to make the final product. The second step is the production of tapes, lamination, and finally co-firing. In our study, firstly, glass frits were wet milled to obtain glass powder. Dried glass powders were pressed at 300 MPa by CIP (Cold Isostatic Pressing) technique and sintered at 770 °C to fabricate samples for dielectric characterization. The dielectric constant and dielectric loss of glass composition was measured by an Impedance Analyzer. For the tape casting process, Al2O3 and milled glass powders were mixed homogeneously with a ball mill. LTCC tapes were produced by tape casting method. Certain number of sheets of Al2O3 – glass composite was stacked and laminated at 75 °C for 30 min under 30 MPa pressure.
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