A fracture-mechanics investigation of peeling of the insulating films and wiring metals in a redistribution layer was performed
on three types of photosensitive resins (polyimide, polybenzoxazole, and phenol) by using finite-element analysis with a simplified
three-dimensional structure of a semiconductor package. Based on the interfacial toughness of the insulating films on the wiring
metal, it was predicted that polyimide would peel the least in the temperature profiles of both the temperature cycling and the reflow
process. That result was correlated well with the interfacial toughness at ambient temperature or below. Also, the fatigue crack
propagation path after peeling had occurred was predicted, with the results that in any of the insulating-film materials, the ratio of
the driving force of the crack propagation to the fracture toughness was higher at the interface than in the insulating films and the
fatigue crack propagation path was at the interface. A statistical survey showed that in both the reflow process and temperature
cycling, insulating-film materials for the redistribution layer should be designed effectively for high interfacial fracture toughness at
ambient temperature or below, and also the insulating films should have high elastic modulus and low thermal expansion coefficient.
Consequently, polyimide is the most reliable material for the insulating films of the redistribution layer.
The free-electron density is very important to investigate the nonlinear absorption phenomenon, which strongly relates to the
joining characteristics such as mechanical strength in fusion micro-welding of glass material by an ultrashort pulsed laser. In this
study, the free-electron density distributions for different numerical apertures (N.A.) were simulated, and photoelasticity observation
and the mechanical strength in micro-welding of glass was experimentally investigated. N.A. 0.45 has a large difference of free-
electron density in beam axis, and the area of large principle stress is generated. On the other hand, N.A. 0.65 can obtain small
difference of peak electron density in the upper and lower parts of molten area, which led to continuous molten area formation. This
joining characteristic resulted in small area of large principal stress difference and high mechanical strength.
Wire harnesses for airplanes are manufactured by bundling multiple wires together with strings by human workers. We designed a
guide part to develop a tool to improve the efficiency of the bundling process. We proposed a method to calculate the optimal path in
the whole process while minimizing the number of predetermined design parameters, and made a prototype of a guide part with the
path determined by this met hod for verification.
With the increase in the power densities of power modules for hybrid vehicles, epoxy-resin-molded components have recently
been explored for high-temperature operation that could cause delamination of the resin from the copper substrate because of their
different thermal expansion coefficients. Therefore, we propose a method of resin adhesion to the copper substrate using amorphous
thin films with inorganic and organic characteristics. The amorphous thin film was deposited on the copper substrate by a plasma-
enhanced chemical vapor deposition（C VD）. In the previous work, it was reported that a high adhesive strength of 30 MPa or more
was obtained between the resin and copper substrate with a C-H-Si amorphous thin film.
To evaluate the influence of the film-forming conditions on the adhesive strength between the resin and copper through amorphous
thin C-H-Si films, in this study, films were formed on the copper substrate at different surface roughness and oxidation states, with
subsequent comparisons of the adhesive strengths. It was observed that an increase in the surface roughness and oxidation time
resulted in increased coverage of the film-formed grains. Additionally, regardless of the microroughness of copper, higher coverage
of the formed grains（approximately 200 nm）enhanced the adhesive strength, thus providing a high adhesive strength of about 35
MPa at a coverage of 60% or more. The film-formed grains also had good wettability with the resin. It is presumed that owing to the
chemical affinity between the CHx groups of the formed grains, a high adhesive strength of 28 MPa could be obtained even at a low
coverage of 15%.
These results reveal that the chemical affinities of the film-formed grains of the C-H-Si film with the resin and the anchor effects
due to the nano-unevenness of the grains contribute to the adhesive strength between the copper substrate and resin through the C-H-
In recent years, the electrification of vehicles has progressed rapidly, and in order to further improve fuel efficiency, it is required
to reduce the size and weight of the system. In dust core using the powder of soft magnetic alloy, in order to reduce the size
and weight, it is required that the material has low core loss and high saturation magnetic flux density. Therefore, we developed
nanocrystallline powders by pulverizing soft magnetic alloy ribbons with low loss and high saturation magnetic flux density. We
clarified the influence of the pulverization method by machine crushing and the nanocrystalization method by heating of pulverized
powders on the magnetic properties. As a result, distortion during pulverizing was suppressed by the cyclone mill method.
Furthermore, nanocrystallization by the heat press method enables uniform heating without thermal runaway, so that the target
values of coercivity and saturation magnetic flux density, which are important magnetic properties, was achieved.