Search

There have been many studies on replacing Au bonding wire with other bonding wire materials, because the cost of Au has dramatically increased by approximately 2~3 times in recent years. When replacing part of the bond pad with a noble metal, Ag bonding wire is of particular interest due to its superior electrical properties, lower cost and similar mechanical properties as compared with Au. Ag bonding wire is thermosonically bonded to 3 kinds of bond pad (Al, Au and Pd) and aged at high temperature (175°C). Then, the bondability and interface reactions are characterized at each bond pad. In the case of Ag-Al bonding, 2 kinds of intermediate phases were observed and the composition ratios of Ag and Al in these phases were 4:1 and 2:1, respectively. After 300 hrs of aging, cracks were formed in these intermediate phases and ball-lift failure occurred. However, in the case of the noble metal bond pad, a solid solution was formed between the Ag wire and bond pad and no voids or cracks were formed. This shows the robust bonding characteristics. The diffusion layer was observed and the diffraction pattern was analyzed by TEM (Transmission Electron microscopy). The Au-Al bond reliability was also characterized by a comparative study. In this study, Ag bonding wire is proposed as an alternative to Au bonding wire for noble metal pads. Also, the thermal reliability is reviewed and the failure mechanisms are verified with various bond pads.

Various Au bonding wires which have different diameters from 25 um to 12 um, and purity of 2N and 4N are used for studying possible problems in ultra fine wire bonding. As wire diameter gets finer, grain size gets finer and portion of direction in wire texture is increased due to high working ratio. Moreover, as wire diameter gets finer, eccentricity of FAB (Free Air Ball) get worse and, for soft 4N wire, neck broken issue is occurred in 12 um bonding due to low neck strength, and for hard 2N wire, bond-off issue is occurred due to bad initial bondability. Also initial IMC (Intermetallics) coverage gets worse and HTST reliability is dramatically dropped in ultra fine wire application. Therefore, soft 2N wire which has relatively low FAB hardness and Pd-based dopant composition could be an alternative to solve these issues in ultra fine wire.

By environmental and technical reasons, the amount of distributed generation will considerably increase in the future power system. As a large number of distributed resources with diverse characteristics have been installed in the distribution system, concerns in the aspect of engineering and operation are focused on the development of new control approaches. This paper discusses how to operate these distributed resources to achieve the maximum benifit. While the output of thermal units is controlled voluntarily by the owner of distributed resources, the power from PV system fluctuates according to the insolation and the atmospheric temperature. Therefore, in order to solve these complications, the optimal model for the operation of mixed distributed resources, such as photovoltaic, diesel and CHP, is proposed in this paper. The customer demands are compared with the resources output to find optimal point of system operation, and in addition, the methodology in this paper can be used for evaluation of economic profit by distributed resources. (5 pages)