Yoshihiko Imanaka

In order to minimize the module substrate, thin film with high capacitance density is required. Aerosol Deposition (ASD) is the unique technique which can make ceramic thin film at room temperature. We have examined ASD technology to apply filter and capacitor embedded in a resin build-up packaging substrate. In this study, we observed the microstructure of BaTiO3 ASD and nano-capillary films, and evaluated the dielectric properties of these thin films.

記事種別: 特集

Aerosol deposition (AD) is a novel ceramic coating method using room temperature impact consolidation (RTIC) phenomena for ceramic fine powder. This method has a wide range potential for fabrication of integrated micro devices and novel nano composite materials. This report reviewed the development of dielectric layers fabricated by AD method at first. BaTiO3 and BaSrTiO3 system thin and thick films were successfully fabricated on Cu substrates at room temperature by employing an AD method. Their dielectric permittivity and dielectric loss tangent were enhanced to approximately 90-120 and 1-1.5 % at 100 kHz, respectively. After annealing at 300C in air, their dielectric permittivity also increased up to approximately 200-300. Finally, we could obtain the capacitance density of 300 nF/cm2 for the ADM-derived BaTiO3 film. As-deposited BST (x=0.6) film at R.T. even showed a tunability of 15 %. At the BST(x=0.6) film annealed at more than 400C, a high tunability of 30% can be obtained at an applied electric field of 150 kV/cm. Embedded capacitors and RF filters were also fabricated.

Aerosol Deposition enables to deposit the ceramic film around room temperature with a nozzle, by making use of the solidification with bombardment of nano-size ceramic particles which are accelerated near sound velocity. We have researched the embedded passive organic substrate with multi-layered high-dielectric constant ceramic condenser. We have conducted the deposition technology of the aerosol deposition of BaTiO3 and clarified that the condenser with the dielectric constant of 400 (max) and the capacitance density of 300nF/cm2 could be formed on the printed wiring board. In this study, we report the relationship between the micro-structure of AD film and the dielectric properties in various reliability test such as the thermal cycle test, pressure cooker test and so on.

Miniaturization, cost reduction and higher performance in RF wireless communication products are demanded for constructing a ubiquitous computing network system. To fulfill these demands, we propose an organic built-up circuit board with various embedded passive ceramic component films for the next-generation RF modules.<BR> In the circuit board we propose, ceramic films have to be built-up on a resin substrate at a temperature lower than the endurance temperature of the resin. Our novel aerosol deposition (ASD) method through the use of accelerated ceramic nano-particle bombardment is therefore one of the most effective deposition methods for the ceramic film.<BR> We describe a novel ASD approach to fabricate embedded capacitors on organic flame retardant type 4 (FR-4) substrates and the correlation between the microstructure and dielectric properties of ASD dielectric films deposited under various conditions. We also confirmed the formation of dense BaTiO₃ dielectric films on organic substrates at room temperature. Embedded capacitors on an FR-4 substrate, fabricated as a prototype with this ASD film, had a capacitance density of 300 nF/cm².

Embedding various passive elements, such as capacitors, filters, and inductors, in one system module, is an effective way to achieve miniaturization, cost reduction, and higher performance in RF communication products. Low Temperature Cofired Ceramics (LTCC) is one of the current promising technologies for obtaining the embedded module. However, one drawback is relatively high-cost. For low-cost RF modules in next generation, we propose a resin built-up circuit board embedding the ceramic passive film using the unique aerosol deposition (AD). This circuit board makes it possible to obtain all of the above demands simultaneously. AD making use of the solidification with bombardment of nano-size ceramic particles can form a ceramic-film below endurance temperature of resin. Therefore, this deposition is the key method for our proposed printed wiring board (PWB) embedding the passive elements. We present the microstructure and properties of the BaTiO3 AD film for the decoupling capacitor in a PWB.