Hyo-Tae Kim

Fabrication of Nonsintered Alumina?Resin Hybrid Films by Inkjet-Printing Technology

We used the inkjet printing to fabricate alumina–resin hybrid films without a high temperature sintering process. Single- and co-solvent ink systems showing different evaporation behaviors were formulated in order to understand their impacts on the inkjet-printing of the alumina dots, lines, and films. The packing densities of the inkjet-printed alumina films from both ink systems were around 60% which is higher than the value obtained by other conventional methods. Since the high temperature sintering process was avoided, the polymer–resin was infiltrated through the inkjet-printed alumina films by the same inkjet printing as a binder. The microstructures of these hybrid films were investigated in order to confirm if the microvoids in the films were filled with the resin. The dielectric properties of these hybrid films such as relative permittivity and Q-value were measured in order to assess if these hybrid materials is applicable to three-dimensional (3D) system integration as ceramic package substrates.

Inkjet-printing of nonsintered alumina-resin hybrid films and their dielectric properties

We used the inkjet printing method to fabricate alumina-resin hybrid films without a high temperature sintering process. The dielectric properties of the alumina-resin hybrid films were studied in order to assess if the alumina-resin hybrid films are applicable to the electronic package substrates. Various numerical models were introduced to understand the relative permittivity of the alumina-resin hybrid films. Q-values of the alumina-resin hybrid films are also measured and compared to the commercially available substrate materials. The impact of microvoids on the Q-value of the inkjet-printed alumina-resin hybrid films was also studied. The microstructures of the inkjet-printed hybrid materials were investigated in order to confirm if the microvoids in the films were filled with the resin.

에어로졸 데포지션법으로 성막된 Al₂O₃ 후막의 유전특성

Aerosol Deposition Method (ADM) is a novel technique to grow ceramic thick films with high density and nano-crystal structure at room temperature. 1,2 ) For these unique advantages of ADM, it would be applied to the fabrication process of 3-D integration ceramic modules effectively. However, it is critical to control the properties of starting powders, because a film formation through ADM is achieved by impaction and consolidation of starting powders on the substrates. We fabricated alumina thick films by ADM for the application to integral substrates for RF modules. When the as-received alumina powders were used as a starting material without any treatments, it was observed that the dielectric properties of as-deposited alumina films, such as relative permittivity and loss tangent, showed high dependency on the frequency. In this study, some techniques of powder pre-treatments to improve the dielectric properties of alumina thick films will be shown and the effects of starting powders on the properties of AD films will be discussed.

Low-Temperature Sintering and Dielectric Properties of BaSn(BO 3 ) 2 Ceramics

Dolomite type BaSn(BO₃)₂ ceramics with rhombohedral crystal structure has been synthesized via solid state reaction route. Dielectric properties were measured for the samples sintered at 1050~1200℃ for 2 h in air. Dielectric constant, loss tangent, and temperature coefficient were increased with sintering temperature due to the evolution of BaSnO₃, secondary, phase. Optimum dielectric properties were obtained at the BaSn(BO₃)₂ ceramics sintered at 1100℃. CuO/Bi₂O₃ was added. to BaSn(BO₃)₂ ceramics to lower the sintering temperature for LTCC application, then Co and Fe-based coloring agents were added for colorizing the LTCC tape. Typical dielectric properties of BaSn(BO)₂ ceramics with 5 wt% CuO/Bi₂O₃ and 3 wt% Co-coloring agent that sintered at 900℃ were e r ＝9.89, tanδ＝0.92 × 10?³, and TCC＝112 ppm/℃. Thus obtained LTCC tape was co-fired with Ag paste for compatibility test and revealed no sign of Ag reaction with the ceramics.

Structure and Properties of Polymer Infiltrated Alumina Thick film via Inkjet Printing Process

We have successfully fabricated the alumina thick films using inkjet printing processes without a high temperature sintering process. Alumina suspension as dielectric ink was formulated by combining nano-sized alumina powders with an anionic polymer dispersant in formamide/water as co-solvent. The thickness of the printed alumina thick film was measured at around 5 um by field emission scanning electron microscope. The calculated packing density of 68.5 % from the printed alumina thick film was much higher than the same films fabricated by conventional casting or dip coating processes. Q factor of the dielectrics thick film infiltrated with cyanate ester resin was evaluated by impedance analyzer.