The amount of halogenated dioxins in combustion gases of printed circuit boards depends on the concentration of halogen in the substrate, and also changes with resin structures to be applied. In this study, it was revealed that by combined use of fine aluminum hydroxide, phosphate flame retardant and alicyclic epoxy resin instead of halogenated epoxy resin or aromatic epoxy resin, these printed circuit boards met UL94-V0 flammability classification. Furthermore halogenated dibenzodioxin/dibenzofuran was hardly detected in combustion gases. The printed circuit boards which consisted of alicyclic epoxy resin could control generating of halogenated dioxins, as compared with aromatic resin. According to the heat decomposition behavior, it was suggested that alicyclic resin was easy to decompose because of weak C-C bond strength and generating of halogenated dioxins were controlled by the structure of resins.
Electric devices with semiconductors are applied to all apparatus including substation equipment, transport machines, home electronics, and cellular phones. Power modules deal large current, and high frequency/optical modules control GHz band signals. As a result, these semiconductors have more than 100 times heat density of memory or MPU chips. Pb-rich high temperature solder and expensive Au-rich solder are applied to these modules, however, thermal stress might be a problem not only for long-term reliability but also for the initial characteristics. The authors studied the assembly of these electric devices using conductive adhesive as a substitute bonding material. We proved that atmospheric aluminum oxides caused electric resistance and that power chips with long rectangle sides over 10 mm have a much larger thermal resistance than theoretical values. We found that it is effective to scratch and remove these oxides through transferred adhesive on aluminum electrodes and to diebond them onto the solder projection previously formed on the die pads.
Recently, the wave of car computerizing is surging such as electronic control unit, car navigation system, electronic toll collection system, car to car communication system, etc. The use environment of in-car devices is under combined environmental stresses such as thermal stress, vibration, and humidity. In general, the reliability of the joints of the devices is individually tested by the evaluation methods for each stress. Our main purpose of this study is to construct the evaluation method for the damages of solder joints under multiple environmental stresses. We investigated the relationship between the plastic strain caused by one cycle vibration stress calculated with FEM analysis considering the temperature dependency of the elasto-plasticity and the fatigue life obtained by the vibration experiment. We indicated the adequacy of the analysis by the correspondence of the resonance frequency of the BGA package mounting board with the experimental result. We also showed that the plastic strain concentrating position corresponded to the crack position. We clarified that the creep strain rate in the total strain was less than 1 percent. We demonstrated that we could apply the power-law equation to predict the fatigue life of the vibration stress from plastic strain rate under 80°C and 125°C as well as the room temperature.
The purpose of this study is to experimentally investigate the co-firing characteristics of different kinds of wastes in circulating fluidized bed combustors, and further to correlate the acquired combustion efficiency with fuel property parameters. The tested individual fuels were wasted tire, RPF, wood tip, RDF and coal, which typified the fuels with distinctively different contents of volatile matters. Coal was employed to represent the fuel containing particularly low volatile matters. The experiments were carried out in a pilot circulating fluidized bed combustor, and varied parameters included the fuel blending ratio, furnace temperature and secondary air ratio. The acquired results indicated that co-firing wasted tire and RPF led to higher CO concentration in the flue gas than firing RPF independently, and this CO concentration increased with increasing the blending ratio of wasted tire. The lower volatile matter content, higher carbon to hydrogen ratio (C⁄H ratio) and carbon to oxygen ratio (C⁄O ratio) of wasted tire than those of RPF were suggested to be responsible for the results. The study also found that the available combustion efficiencies in co-firing various pairs of the tested fuels were correlative with the volatile matter contents, C⁄H and C⁄O ratios of the blended fuels estimated as the weighed sums of the same property parameters of individual fuels. This allows thus a simple determination of the co-firing efficiency of any fuel blend from calculating the blend′s fuel property parameters using the fuel blending ratio as a weight.
We have tried to produce TiNi intermetallic compounds from six type composite wires of pure Ti and Ni. The composition of a coating layer was changed by changing the diameter of Ni wire. The composite wires were melted and reacted using a laser, and the melted metal was coated on an aluminum substrate in Ar gas flow. There were many pores and cracks in the coating layers. But, the defects of the coating layers could be reduced to 0.1% or less by the post hot-press treatment. The hot pressed specimens with Ni content of 48% to 50% consisted of martensite and austenite phases. The Mf and Af temperatures were 326K and 372K , respectively, and the stress recovery obtained was 160MPa.
An approach to combine a friction heat input model with a non-steady heat conduction analysis has enabled a numerical simulation of a heat input and a transient temperature distribution in friction welding processes. This report describes the result obtained by applying this approach to the friction welding process of two similar materials of S25C carbon steel or SUS304 stainless steel. When base metals are different, the friction heat input model and the thermophysical property data are changed depending on a quality of base metal. Comparison between a calculated result and an experimental result was carried out, and appropriateness of this approach was examined. Furthermore, a difference of temperature distribution in friction welding region with the difference of thermophysical property of base metal was examined, and also the heat-affected zone was investigated. As a result, it was verified that this approach could simulate a characteristic of a welding process in brake-type friction welding. And the calculated results agreed with the experimental results on a difference of quantity of heat input to be caused by a difference of a friction welding condition. A difference of a temperature history caused in a different base metal appeared to be estimated from a calculated result, and it was confirmed that this approach was appropriate. The width of heat-affected zone was estimated by an calculated result of the maximum temperature distribution in the vicinity of friction surface by using this approach combining a friction heat input model with a non-steady heat conduction analysis.