We have previously proposed an optoelectronic hybrid packaging configuration based on the concept of separating optical and electrical interconnections in the board-level optical interconnection. The proposed board consists of a plastic optical fiber wiring sheet with an“opening”equipped with right-angle-turn optical interface connector for interconnecting optical-I/O interface multichip modules. This paper mainly describes the benefit of the board configuration, the first demonstration of the plastic optical fiber wiring sheet with an opening, and basic optical characteristics of the optical right-angle-turn connector.

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Recently, preventing environmental pollution, lead-free (Pb-free) solders are about to replace tin-lead (Sn-Pb) eutectic solders. However, the mechanical properties of Pb-free solders have not been clarified. Hence, the following study was conducted; First, a rate-dependent plasticity was characterized to represent the inelastic deformation behavior for Sn-Ag-based lead free solders. The material parameters in a constitutive model was determined in a direct method combining both rate dependent and rate independent plastic strains. The constitutive model unifies both rate-dependent creep behavior and rate-independent plastic behavior occurring concurrently at the same time in the solders. Secondly, the strength of solders with a variety of plating materials was studied. Intermetallic compounds between solder and electrical pads are formed during reflow process and gradually grow in service. By using the Cu-plates on which Cu or Ni or Ni/Au plating was deposited, the specimens of solder joints were fabricated with Sn-Ag-based lead free solders. After aging the specimens in an isothermal chamber, tensile tests were performed. From SEM microscope observation and EDX microprobe analysis, the growth and components of the intermetallic compounds layer were also examined. Based on the experimental tests, the relations between solder joint strength and the aging period were discussed.

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The relationship between LSI operation modes and radiated emission, and reduction measures were studied by using Test LSI. Output operation that drives many external traces radiates a large amount of emission. Insufficient return paths for external trace currents at LSI mounted area result in high frequency current loops, which excite the power and ground plane and cause widely distributed high frequency currents over the PCB. Putting ferrite on LSI package and covering LSI package with copper sheet effectively reduce the extent of the current distribution over the PCB and reduce the emission.

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The application of anisotropic conductive films (ACF) to form interconnections between chips and substrates is one potential variation of flip chip technologies. Its appeal comes from the possibilities of forming very fine pitch interconnections that are not feasible with solder, avoiding the use of lead, and achieving simpler, lower cost processing. In this study, we evaluate the interconnection reliability of ACF joints based on a contact conductive mechanism by using a contact analysis. We have clarified the influence of the material properties of the ACF and the build-up substrate on the interconnection reliability during temperature cycling. The key factor that dominates the interconnection reliability is the amount of plastic strain of the Au bump at the contact face. Therefore, it is very important to control the plastic deformation of the Au bump. On the other hand, we found that the interconnection reliability during moisture resistance testing may deteriorate due to stress relaxation at near the grass transition temperature of the commonly used build-up material.

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A new replication process with a silicon-oxide antisticking layer was demonstrated using a fluorinated polyimide. A thin silicon-oxide coating was introduced on the top of the mold as the antisticking layer, which could significantly improve the separation between the mold and the fluorinated polyimide film without degrading the optical property. A single- and a multimode waveguide film were fabricated using a cladding film with grooves formed by our replication process. The waveguide exhibited very low optical propagation losses of 0.30dB/cm and 0.36dB/cm at the wavelengths of 1310nm and 850nm, respectively. In addition, a 2-layer polyimide waveguide and an electrical-optical printed circuit board (EOPCB) were fabricated easily by hot-pressing method, using the fluorinated polyimide waveguide and a fluorinated poly (amic acid) film as an adhesive layer.

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Validity of finite difference time domain (FDTD) method is examined by evaluating the absorption performance from the variation of Q factor under the condition that the absorbing material is inserted into a cavity resonator. The magnetic field distribution in a cavity resonator is visually observed. As a result, we confirmed that the decreasing rate of Q factor was agreed with the calculated and measured results, and both corresponded in the difference in 2 percent. Consequently, validity of FDTD method for examination mentioned above is confirmed. We confirmed that magnetic field distribution in the cavity resonator was drastically weaken when the absorbing material is inserted into the cavity resonator.

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[in Japanese]

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The electroless Ni-B plating has attracted for the application of the electronics fields. However, it has not achieved to improve of bath stability and bath life yet. Accordingly, bath stability, deposition rate, boron content and wettability of the deposited films were studied using thirty kinds of complexing agents. Since, the reducing power of DMAB is stronger than the other reducing agents, bath stability is able to be improved by the balance of the reducing power and selection of complexing agent. Boron content in the deposited films decreased from 6wt% to 2wt% with increasing the deposition rate at the acidic region. On the other hand, boron content in the deposited films under alkaline region did not much influence by the bath pH and showed less than lwt%. Generally, tensile stress of deposited Ni-B films is higher than the Ni-P films. However, when the sulphur compounds are added in the plating bath, the stress can be greatly reduced.

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Correlation between composition and shrinkage cavity of Sn-Ag-Bi-Cu lead-free solder alloys was investigated. Incidence of surface cracks on solder fillets, caused by shrinkage cavity, was significantly influenced by Ag content of solder alloys (1.0-2.5wt%) ; for solder fillets with less than 2.0wt% of Ag content, surface cracks decreased in accordance with a reduction in Ag content. On the other hand, incidence of surface cracks was independent of Bi content of solder alloys (0-4.0wt%) . Compositional mapping analysis with EDX revealed that less Ag₃Sn phases were formed for solder fillets with less Ag content, suggesting that the formation of the Ag₃Sn/Sn eutectic network band triggers the formation of surface cracks, i.e., shrinkage cavity. Wettability of solder alloys with various Ag contents was also investigated. It was clarified that a decrease in Ag content leaded to degradation of solder wettability, indicating an increase in liquidus temperature of solder.

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Surface breakdown phenomenon of printed wiring board was investigated under decreased pressure from 100kPa to lkPa. The experiment was carried out by do pulse voltage with the frequencies in the range of 50Hz to 200Hz. Printed wiring boards of epoxy resin laminate have been employed to investigate the effects of atmospheric pressure and the frequencies of applied voltage on the discharge quantity. The study revealed that the time to breakdown increases with lowering pressure, and it decreases with increasing the frequency of applied voltage. The characteristics of discharge currents under decreased pressures and the frequency were discussed by using power spectral density of discharge current. The results show that the power spectral density of discharge currents decreases at 100Hz, but increases at 200Hz as the atmospheric pressure decreases.

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Recently miniaturization and performance enhancement of electronic equipment are remarkable. The gap between the conductors on a printed circuit board becomes much smaller, and the high insulation reliability is required for the printed circuit board. In the printed circuit board, it is also abounding in the opportunity of which various surge are applied, and it is abounding of printed circuit board of which the inverter surge is always applied by the development of recent power electronics. From such background, surge dielectric strength between printed circuit board conductive foil was examined. The experiment was carried out by FR-4 model printed circuit board. As a result, surge dielectric strength of the 0.03mm-0.5mm gap length sample was 0.2kV-2.5kV. In the sample with solder resist coating, surge dielectric strength between conductive foil was 9kV-10.5kV.

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