This paper describes the bondability of thermosonic flip chip bonding, in which ultrasonic (US) vibration perpendicular to the interface was applied. Experiments were carried out with a device chip having 11 Au stud bumps and a ceramic substrate having Au-plated bonding pads. The stud bump was used to investigate bondability when the bump was largely deformed. The height reduction ratio of the bump was changed from 38% to 64% by changing bonding load and US amplitude. The relationship between the height reduction ratio of bump and shear strength of the bond was compared with that using US parallel to the interface. It was found that the bonding using US vibration perpendicular to the interface requires bonding load and US amplitude above a certain level to obtain high bond strength. When the height reduction ratio of the bump became bigger than 60%, bond strength of approximately 100 MPa was obtained. This strength was higher than bond strength of the bonding using US vibration parallel to the interface.
Ideal microrobots are on the millimeter-scale with integrated actuators, power sources, sensors, and controllers. Numerous researchers are inspired by insects for the mechanical or electrical design of microrobots. Previously, the authors proposed and demonstrated microrobots that can replicate the tripod gait locomotion of an ant, the legs of which were actuated by shape memory alloy (SMA) actuators. The SMA provided a large deformation and force, but the power consumed by actuating a single leg reached as high as 94 mW. This paper discusses a silicon electrostatic inchworm motor chip to move a robot leg with low energy consumption using a small power source. The inchworm motor chip was actuated by electrostatic motors. The power consumption was as low as 1.0 mW, in contrast with SMA actuators. The reciprocal motion of the inchworm motor chip is powered by silicon photovoltaic cells. The results show that the 7.5 mm2 photovoltaic cells could produce 60 V to actuate the inchworm motor chip, and the generated force is enough to move the leg of the microrobot. Thus, we demonstrated the actuation of a microrobot leg using an electrostatic inchworm motor chip, which is the first reported instance of an electrostatic motor driving an off-chip structure.
This paper is the progressive study of previous papers presented at the IMPACT 2015 and ICEP 2018, and evaluates effectiveness and applicability of MLCS (Memory Logic Conjugated System) with a simple deep learning processing. NVIDIA, Google, Fujitsu Intel-Altera, Intel-Nervana and Renesas recently announced that 8 bits processing can keep efficient and flexible AI computation, peculiarly in deep learning. This paper discusses on the actual MLCS circuit implemented on a commercial FPGA for deep learning, and evaluate the circuit with perceptron method for deep learning. In the MLCS architecture, deep learning computations can be done as memory operations. Our architecture can achieve its high I/O bandwidth and low-power consumption with dynamic reconfiguration functionality, high-speed connection among logics and memory cells, and low implementation cost.
Novel aluminum nitride (AlN) fillers with large particle size and round shape were developed using the carbo-thermal reduction and nitridation (CRN) method in this study. They were used as high thermal conductivity fillers for resin composites. Thermal conductivity of epoxy resin filled with the AlN filler could reach 12 W/m K. The fluidity of the epoxy resin filled with the developed AlN filler was improved to 1.3 times that of conventional resin. Also, viscosity of silicon resin filled with the AlN filler was one tenth lower than the conventional AlN filler. The properties and evaluation of the developed AlN filler for high thermal conductivity packaging material have also been discussed.
High thermal conductive adhesive having extreme low interfacial thermal resistance was developed for thermal management of power device and modulus. We focused on reducing an interfacial heat resistance between high thermal conductive sheet composed of resin and heat conductive filler and metal such as Cu or Al. The interfacial thermal resistance was determined by modulus of heat conductive sheet and dispersion of high heat conductive filler. The low modulus sheet and the good dispersed sheet showed lower interfacial thermal resistance. In addition, we investigated the effect of filler size. The larger filler size showed higher heat conductivity and higher interfacial thermal resistance. To consider the effect of those facts, we successfully developed the high thermal conductive sheet with extremely low interfacial thermal resistance. Bulk heat conductivity of the sheet is higher than 10 W/mK. The interface thermal resistance is below 0.009 K/W.