With the increase in the power density of power modules for hybrid vehicles, the resin-molded components have recently been
required to operate at high temperatures, which could cause the delamination of the resin layer from the copper (Cu) substrate
because of their different thermal expansion behavior. Generally, nickel–phosphorus (Ni-P) plating is applied to the Cu substrate
and primer pretreatment is performed prior to resin molding to enhance the adhesion strength between the resin and Cu substrate.
However, the use of a primer has several disadvantages such as increasing the cost and complexity of the manufacturing process.
To decrease the number of process steps, we changed the film plated on the Cu substrate from Ni-P to a carbon–hydrogen–silicon
(C-H-Si) amorphous material prepared using a plasma-enhanced chemical vapor deposition (CVD) method. A resin–Cu bonded
specimen was then prepared by forming epoxy-based resin on the C-H-Si-coated Cu substrate. The adhesion properties of the
specimen were evaluated by conducting a shear bonding test.
The test results indicated that the specimen maintained a high interface strength of 30 MPa even after heating at 473 K for 1000
h. Such a high bonding strength seems to be derived from both physical and chemical factors. One is an anchor effect originating
from the nanosized morphology on the film surface. The other was the good chemical affinity between the resin and film. The film
contained CHX groups, which would have good wettability for the CHX groups in the resin, and hydroxyl groups, which would form
hydrogen bonds with hydroxyl groups in the resin.
The purpose of the present study is to supply the design guidelines of the high accuracy bonding process concerning the assembly
of the semiconductor packages such as 2.5D, 3D and fan-out wafer level package. In this study, the target of the bonding accuracy
of the die-attach process is within 3 μm. The authors fabricated the bonding unit consist of the transparent head and the sideview
camera, which can directly recognize the alignment mark chucked on the bonding head. In order to solve the issue that the
recognition accuracy becomes worse by the thermal fluctuation, the authors quantified the thermal-fluid behavior by the thermal
fluid analysis and the particle image velocimetry, and clarified the correlation between the control factors of the recognition accuracy
in the bonding process. Furthermore, the condition to reduce the thermal fluctuation was found, so that the bonding accuracy of ±3
μm was achieved in the die-attach process.
Silicon-based materials are widely promising electronic components by the combination with metals in power electronics field.
Joining between metal and Si-based materials, e.g., Si and SiC, substrate generally requires the indirect process involving specific
surface modification such as metallization because of their characteristics of chemical bond. In this study, we report the metal-tosilicon
joining without surface treatment such as metallization by using the decomposition reaction of silver oxide. The interfacial
microstructure of Si/Ag significantly changed before and after the thermal decomposition of Ag2O. Ag bonded to silicon-based
materials through a thin SiO2 layer before thermal decomposition. In contrast, Ag bonded to silicon-based materials through a thick
SiO2 layer containing Ag nanoparticles after the reaction. MD simulations revealed Ag atoms embedded in SiO2 near the surface
contribute to the bonding between Ag and SiO2. It was concluded that the joining is due to the presence of Ag inside SiO2 regardless
of the thermal decomposition, determining the interfacial microstructure.
Thermal warp of a printed circuit board（PCB）is largely influenced by the cure shrinkage reaction of thermosetting resins, as
well as the mismatch in the residual copper rate of conductive layers and the coefficient of thermal expansion（CTE）of substrate
materials. In this study, the thermal warp in a substrate consisting of only resin was simulated under the manufacturing process
condition of the resin substrate. As a result of reflecting the viscoelastic properties and the CTE of the incompletely cured resins in
the warp simulation, the warp behavior of the resin substrate was accurately predicted.
Recently, getting more reduction of energy consumption is attracting the attention in not only the society but also the industries.
Therefore, the industries require pre-evaluation methods and production management methods to reduce energy consumption while
maintaining productivity. On the other hand, in industry, defective products occur in the production process. The defective products
affect lower productivity and waste of energy consumption, which affect will the specific energy consumption. However, research on
evaluation method of the specific energy consumption considering the defective products has not conducted. Therefore, we propose
a formula for quantitative evaluation of the specific energy consumption in production line considering the defective products.
We also verify the validity of the proposed formula using a manufacturing system simulation. In a case study for a semiconductor
manufacturing line, the specific energy consumption results by simulation and our proposed formula are compared. We confirmed
that our proposed formula could accurately calculate the specific energy consumption. In addition, it was clarified that the specific
energy consumption is increased by decreasing productivity due to the generation of defective products and by increasing the waste
of energy consumption at periods in running states and idle states.
Detwinning behaviors in bismuth single crystals were investigated by applying cyclic strain for a single cycle in the [2¯1¯10]
and [10¯10] directions. The obtained hysteresis loop and the results of in-situ observations were carefully examined and these data
showed that twins formed in tensile process were disappeared (detwinning) in the compression process. In-situ observations and the
results of EBSD analysis also showed that the detwinning occurred from a twin boundary with the crystallographic orientation of the
twin being maintained. It can be thought that the detwinning was caused by the movement of twinning dislocations by the assistance
of stacking fault energy at the twin boundary.
Power devices are often sealed either silicone gel or epoxy resin including silica filler to prevent chip and joints from chemical
and mechanical stress. To reduce the stress and strain at both Si chip and solder joint, a novel structural model that a thin interlayer
having low elastic modulus was inserted between sealing resin and Si chip was proposed. It was revealed that the polyester-modified
epoxy resin exhibited lower Young’s modulus at 25℃ and 125℃ than that of the epoxy resin, and it could be expected as the
interlayer. The interlayer was shown to have an optimum thickness in terms of the stress on the chip and the thermal resistance of the
module. The validity of these structural analyzes was shown by simple experiments.
When alternating current (AC) is used in tungsten inert gas (TIG) welding, the shape of weld penetration is known to be largely
changed depending on electrode positive (EP) polarity ratio which is defined as a ratio of EP period occupied in one cycle of
current waveform. This fact implies that heat transport processes between electrode negative (EN) and EP polarity are significantly
different to lead to different temperature distribution of weld pool. However, these processes have not been understood clearly,
because they are thought to be directly linked to the complex cathode spot behavior. This study aims to discuss difference in heat
transport processes between EN and EP polarity in AC TIG welding of aluminum A1050 by comparing temperature distributions in
both polarities measured with two colour pyrometry taking into account the cathode spot behavior. As a result, it was found that the
temperatures at the center in EN were greater than that in EP and decreased gradually toward the edge of the weld pool. Moreover,
the temperature in 30% EP polarity ratio was higher than that in 10% EP polarity ratio. Consequently, the heat flux produced by
cathode spots is suggested to significantly affect the surface temperature distribution of weld pool as well as the weld shape. The
heat flux distribution in EP polarity is considered to become not Gaussian but ring-shaped. Furthermore, the reason to achieve higher
average temperature in 30% EP polarity ratio is explained by longer heating through cathode spots.
This study aims to reduce diffusible hydrogen in GMA and FCA welding. For this purpose, a novel welding torch with a dual
structural gas nozzle, which enables to suction hydrogen source gas evaporated from a wire, has been developed. In order to improve
the suction efficiency of this evaporated gas, precise control of the suction gas flow is indispensable. In this paper, as the first step
of research, ignoring the evaporation of hydrogen source gas from the wire, only influence of the suction nozzle structure and torch
operating condition on the suction gas flow pattern was investigated through numerical simulation. As a result, it is suggested to be
especially effective in reducing diffusible hydrogen to extend the suction nozzle length within a range not disturbing the arc, or to
design a nozzle structure that provides an equivalent effect with the extension of suction nozzle length.