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Wire bonding is still the most popular chip interconnect technology in microelectronic packaging and will not be replaced by other interconnect methods for a long time in the future. Au bonding wire has been a mainstream semiconductor packaging material for many decades due to its unique chemical stability, reliable manufacturing, and operation properties. However, the drastic increasing price of Au bonding wire has motivated the industry to search for alternate bonding materials for use in microelectronic packaging such as Cu and Ag bonding wires. The main benefits of using Cu bonding wire over Au bonding wire are lower material cost, higher electrical and thermal conductivity that enables smaller diameter Cu bonding wire to carry identical current as an Au bonding wire without overheating, and lower reaction rates between Cu and Al that serve to improve the reliability performance in long periods of high temperature storage conditions. However, the high hardness, easy oxidation, and complex bonding process of Cu bonding wire make it not the best alternative for Au bonding wire. Therefore, Ag bonding wire as a new alternative with potential application comes to the packaging market; it has higher thermal conductivity and lower electric resistivity in comparison with Cu bonding wire, which makes it a good candidate for power electronics, and higher elastic modulus and hardness than Au bonding wire, but lower than Cu bonding wire, which makes it easier to bond. This paper begins with a brief introduction about the developing history of bonding wires. Next, manufacturability and reliability of Au, Cu, and Ag bonding wires are introduced. Furthermore, general comparisons on basic performance and applications between the three types of bonding wires are discussed. In the end, developing trends of bonding wire are provided. Hopefully, this review can be regarded as a useful complement to other reviews on wire bonding technology and applications.

Abstract：The micro-structure and properties of Ag-4Pd alloy bonding wire after drawing and heat treatment are investigated, and effects of drawing rate and heat treatment temperature on mechanical properties, structure and fusing current of Ag-4Pd alloy bonding are are analyzed. The results show that the strength of Ag-4Pd alloy bonding wire will increase, and the elongation will decrease when drawing rate increased, the main deformation type are flip and twin. For  0.050 mmAg-Pd alloy bonding wire, the broken load decreases and elongation increases when heat treatment temperature increases, the mechanical properties are excellent after heat treatment at 525 ℃. When increase heat treatment temperature more, the twin crystal is found in Ag-4Pd alloy bonding wire, and twin nucleation and subgrain grows are the main nucleation. The micro bamboo defects on surface are found after heat treatment with excessive tensile load. The electrical resistance of Ag-4Pd alloy bonding wire decreases after heat treatment. After data fitting, Ag-4Pd alloy bonding wire fusing current and fusing time is exponential function, and fusing current and loop is cubic polynomial function.

The space charge accumulation is an important factor to design the oil-pressboard composite insulation of convertor transformer, which is greatly affected by the temperature. In this paper, the space charge accumulation and attenuation in the two layers and single layer under DC voltage were studied by the Pulsed Electro-Acoustic Method from 20 • C to 60 • C, and the electric field distribution was calculated by the space charge distribution. The studied results have indicated that the distributions of space charge and electric field in the test results do not follow the Maxwell-Wagner polarization. The space charge distribution is affected by the surface trap, bulk trap, charge migration and electric field. The temperature affected the polarity and amount of the charge at oil-pressboard interface. The space charge accumulation of the two layers is more complex than that of the single layer, and the space charge accumulation and attenuation of two layers need longer time to reach the stable stage. The space charge accumulation in the single layer is largest at 40 • C, whereas the space charge accumulation in the two layers is largest at 20 • C. Moreover, the increase in the temperature increases the attenuation amplitude and speed of space charge. INDEX TERMS Space charge, two layers, oil-pressboard insulation, temperature.

AbstractIn this paper, the Cu-0.52Ag-0.22Cr alloy was prepared by hot horizontal continuous casting. The effects of aging process on micro-hardness, electrical conductivity, and nanoscale precipitates of Cu-0.52Ag-0.22Cr alloy were studied. The electrical conductivity and micro-hardness increase significantly in the early aging time. With the extension of aging time, the electrical conductivity is basically unchanged and remains at a high level. While, the micro-hardness increases slowly, the change trend is different at 623 K, 723 K, and 773 K. The optimisation of process parameters occurs in 723 K for 2 h. At this time, the electric conductivity is 95.8% IACS and the hardness is 104.1 HV0.1. The XRD result shows that the Ag and Cr are precipitated in elemental form copper matrix. Further TEM shows that, Cr exists at the sub-boundary in the form of larger nanoscale precipitates (100-200 nm). While a large number of Ag nanoscale precipitates (8-10 nm) is dispersed on the copper matrix. The synergistic effect of Ag and Cr nanoscale precipitates significantly improved the properties of the alloy.