The next-generation power devices are expected to be used in high voltage applications. And development of high-voltage power module has been promoted. The key issue in high-voltage power module is the existence of partial discharge (PD). PD deteriorates insulating materials for a long time and finally causes dielectric breakdown of power module. Therefore identifying a fragile site such as PD occurring part is important to make products with high reliability. However, high accuracy PD location test for small size high voltage equipment hasn’t been established. To identify PD location in power module, we establish an algorithm of calculating the time difference of each sensor and identifying PD location. Then we investigate an influence of the sampling frequency in the oscilloscope on the identification results.
Development in computer and network technologies is realizing highly-distributed manufacturing systems (HDMSs) where each facility is computerized and can communicate with each other. Distributed discrete event simulation taking advantage of this hardware environment has been discussed, and an algorithm for priority sequencing by communication among facilities was developed. This algorithm is also applicable to production scheduling with dispatching rules, and a distributed method of job-shop scheduling was proposed. This paper describes enhancement of this method for flexible job-shop where alternative machines exist. Mechanism for updating priority sequence for obtaining intermediate products is developed using that algorithm. Incorporating this mechanism enables application of the previous method to the flexible job-shop scheduling. Feasibility of the proposed method was shown by an example.
Solid-liquid reaction-diffusion bonding using tin film was applied to bond copper, which is a candidate for the die-bond process used in assembling next-generation power devices. Sn-Cu intermetallic compounds formed and grew even during temperatures reaching the melting point of Sn. Eventually, a sound bond layer that was composed of Cu3Sn with some small voids was obtained after complete reaction-diffusion. When the Sn phase remained in the bond layer due to insufficient reaction-diffusion, relatively large defects formed there. Spherical defects also formed in the bond layer when the electroplated Sn film was used as an interlayer, owing to the large amount of gas generated from the film.
The effect of surface modification of insert metal on the bond strength of the bonded interface of aluminum casting alloy was investigated by SEM and EDX observations of bonded interfaces and fractured surfaces. The surface of Zn insert metal was modified by boiling in formic acid and acetic acid, although the surface of the AC2C and ADC12 casting alloy were only polished. Bonding was performed at bonding temperature of 673-733 K under a pressure of 20 MPa (bonding time of 15 min). As a result of surface modification by formic acid and acetic acid, a higher interfacial strength joint is obtained at lower bonding temperature compared with non-modified joints.