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  4. No.34 January,2005
Fujikura Technical Review

No.34 January,2005

Switch module, that is assembled plastic injection molding parts and metal plates with flexible printed circuit, is able to reduce customer's cost and lead time for design, development, and production. And this contributes to price-reduction and minimizing product development term of home electronics equipments, such as a digital video camera and a digital still camera. In addition, when Fujikura which is also a circuit board maker design a switch module, many effects directly connected with cost reduction and development period shortening, for instance we can realize optimal design which anticipate switch module from the initial development stage, or we can unify product reliability evaluation. The demand for a switch module is increasing more and more, and has also expanded the requirement for the further advanced features, together with the increase of digital consumer electronics diffusion in recent years. Fujikura continues proposing these switch module to a customer speedily at low cost and high quality based on our circuit board technique of material and manufacturing that we cultivated in the past.


Holey Fibers for Low Bending Loss

We have developed a novel type of holey fiber which has a conventional raised-index core surrounded by two layers of air holes with different sizes. The fiber has single-mode operation and shows a low bending loss even for an extremely small bending diameter and a low splicing loss for fusion splicing to a conventional single-mode fiber. The structure and the properties of the fiber are reported in this paper. 

Optical Fiber Amplifier with Multi-slot Configuration for Analogue Video Distribution

High-quality and/or multi-channel analogue video distribution services have been widely deployed recently. This trend is increasing the necessity of optical fiber amplifiers. We have developed an optical fiber amplifier - Fujikura optical amplifier model (FOAM) - for analogue video distribution services having a multi-slot chassis for up to 9 EDFA (Erbium Doped Fiber Amplifier) units, dual power-source units, multiple fan units, and an SNMP (Simple Network Management Protocol) control unit. Hot swapping is possible with all the units for easy maintenance. This amplifier was carefully designed to have low distortion, low noise figure, and wide operating wavelength. The outer dimension of 19 in. width with 3 U height was chosen to meet the EIA (Electronic Industries Alliance) standards. To our knowledge as of now, this chassis is the smallest in size with the highest number of EDFA units. In a relatively small system application or so, the one EDFA unit with just 1U height is adequate. We have also developed a unit for such an application. In this report, we describe the characteristics of FOAM Series in detail. 

New Core Alignment Fusion Splicer FSM-50S

For many years, most fiber optic splicing in the core and edges of the network has been predominantly performed by core alignment fusion splicers, which produce the lowest possible splice losses. Customer requirements have continued to evolve, and in addition to low splice losses, customers now require exceptional portability, high yield, fast splicing, fail-safe functions to prevent faulty splices from being made, and skill-free easy operation. Fujikura has responded to these new requirements by developing a new core alignment fusion splicer, which is the fastest, smallest, lightest and easiest to use in its class. 

New Mass Fusion Splicer FSM-50R Series

Fixed V-groove fusion splicers are commonly used in the installation of fiber optic cables, including FTTx applications, in Japan and rest of the world. Splicer users, especially those deploying new FTTx applications, are increasingly requiring splicers to be light and have a compact form factor, in addition to being fast and easy to use. Fujikura has introduced several new fixed V-groove splicers to meet these requirements. The FSM-50R is used to splice up to 12-fiber ribbons, the FSM-17R is used for splicing up to 4-fiber ribbons, and the FSM-17S is used for single fiber splices. Each of these splicers includes multiple advanced features to meet the requirements of customers in Japan and rest of the world. 

Small Film Antenna for Wireless LAN

Previously we have developed a film antenna for wireless LAN available for notebook personal computer (PC). The previous size of the film antenna was 55 mm × 5 mm × 0.1 mm. We recently developed a small film antenna that has a reduced area of 70% this time. This antenna is available for 2GHz and 5GHz bands, and the size of this antenna is 25 mm × 2.5 mm × 0.1 mm. This antenna has omni-directional radiation pattern and high gain, and it is flexible. So, this antenna is suitable for mounting in small mobile devices such as personal digital assistants (PDA). 

Welding Type Connectors for High-Speed Cable

We developed the welding type connector and welding method for high-speed cable, which is based on InfiniBandTM standard. The standard is defined by IBTA (InfiniBand Trade Association) as an interface standard of the next generation. Our cables have a favorable performance for impedance matching and near-end crosstalk under 2.5 Gbps transmission. In the future, it will be applicable to 10 Gbps cable. 

Halogen-Free Multilayer Printed Circuit Boards

With the rise in demand for products that reduce the environmental burden, we began to develop halogen-free rigid-flex multilayer printed circuit boards (R-F PCB). In the process of this development, it became clear that a higher migration resistance in R-F PCB than flexible printed circuit boards (FPC) was required. For this reason, after various characteristic evaluations, through material selection and optimization of processing conditions, we were successful in improving properties to a level equivalent to those of currently mass-produced products. 

Anisotropic Conductive Paste (ACP)

Anisotropic conductive paste (ACP) is a material for connecting two circuits, or a circuit and an electrical device. It includes conductive filler and binder; the conductive filler passes electricity after heat press and the binder bonds the circuits. Anisotropic conductive film (ACF) has the same function as ACP. Fujikura is supplying the membrane switches with ACF connection until now. But ACP is easier to produce and it is cheaper than ACF. So, we investigated the application of ACP, especially for connection between upper and lower electrical sheets of personal computer (PC) keyboards. We successfully used the ACP connection technology with PC keyboards. This technology can be used for connections between circuits and their surrounding electrical parts like liquid crystal displays (LCDs). 

Double-Sided Fine Flexible Printed Circuits

The demand of flexible printed circuit (FPC) has expanded with the advance of electronic devices. Especially, the demand for a fine pattern is increasing with the progress of an additional number of pins and the fine pitch of IC mounted on the FPC. There are three technologies to obtain fine FPC: the first is a finer process, the second is an interlayer connection with microvia, and the third is resist coating. We attempted fine processing technology by the subtractive and the semi-additive process. We have obtained interlayer connection by the laser via hole (LVH) process in order to achieve microvia and high location accuracy. In resist coating technology, we have achieved high location accuracy using coverlay film. Furthermore, we have also established high location accuracy and small area opening. 

Board-to-board Interconnection with Solder Bump

Connectors and anisotropic conductive films (ACFs) have already been applied to a board-to-board interconnection. The authors have focused on board-to-board interconnection with solder bump instead of ACFs, which has been used in flip chip (FC) bonding technology. One of the advantages of this technology is that the boards are connected in a solder reflow process with other surface mount devices on the boards. We have tried to make prototypes of flexible printed circuits (FPCs) and realized the connections in half area of the connectors. Furthermore, we have found highly reliable performance of the connection as same as that of a build-up Rigid-Flex board (R-F board). 

Additive Process for Build-Up Printed Wiring Board

We have developed the build-up conductor pattern by using the additive process. The additive process was more effective in forming a fine pattern of high precision than the conventional subtractive one. The present technique can be applied to the manufacture of a future multilayer printed wiring board that provides small-scale electronic devices with high-density wiring. 

Ultrafine Metallic Particles

Ultrafine metallic particles of Ni, Ag and Cu with an average particle diameter of 400 nm were prepared by hydrogen reduction of metallic chloride vapors. Furthermore, we have developed 100-nm-diameter Ni and Ni-W alloy particles, which have the potential to be applied for ultra small multi-layer ceramic capacitor in the near future. Ni-W particles were in the form of solid solution, in which W elements were distributed uniformly in Ni matrix. It was found that the sintering property of Ni particles was improved dramatically by doping with several wt% of W. 

Highly Conductive Membrane Wiring Board

A membrane-wiring board (MB) is produced by screen-printing of a silver paste on a polyethylene terephthalate (PET) substrate and is used to cure typically at 150°C. Compared with flexible printed circuit (FPC), the advantage of the MB is in its low cost due to the application of simple processes. But the scope of applications has been limited due to the high electrical resistivity that is several tens of times higher than that of FPC, where bulk copper circuits are formed by chemical etching or electroplating technology. We successfully developed a highly conductive silver paste and the MB using the paste (highly conductive MB). The paste realized remarkably low resistance of less than 10-5 Ωcm after curing at 150°C , that is about 1/10 compared with that of a conventional MB. In this paper, the development and performance are introduced.
*1 Aomori Fujikura Kanaya Ltd.
*2 Fujikura Kasei Co. Ltd.  

Dye-sensitized Solar Cells Using Nanocomposite Ion-gel

Dye-sensitized solar cells (DSCs) are expected to be the next-generation solar cell because they can be fabricated at a low cost and use no harmful materials. There are several tasks, which must be undertaken to attain practical use, and as one of those tasks, it is necessary to improve electrolyte materials for improvement of long-term stability and reliability of the cells. We investigated the properties of a nanocomposite ion-gel electrolyte that was a gelated ionic liquid electrolyte with several nanoparticles. The nanocomposite ion-gel type cell successfully attained both increase in conversion efficiency and quasi-solidification of the electrolyte. Energy conversion efficiency of the quasi-solid state-type cell with 5 mm × 9 mm photo-electrode size was η = 6.4% under optimized conditions. In this report, details of the photovoltaic property of the cell are described. In addition, technological subjects in the fabrication of practical DSCs devices are also introduced.
*1 Osaka University
*2 Yokohama National University