This is the new wire evaluation work for the reliability of the wire-bonding process. There is a trend for the plastic integrated-circuit package to function at higher junction temperature with thinner wire. New alloy Au wires have been developed to meet the reliability requirements. Two types of alloy Au wires, Au-Pd and Au-Cu, were evaluated in this study. These samples were aged between 155°C and 205°C under air from 0 h to 3,000 h. According to this study, the phase-formation sequence of Au 2 Al, Au 5 Al 2 , and Au 4 Al intermetallic is similar to the pure Au wire. There is a Pd-rich layer working as a diffusion barrier to slow down the growth rate of intermetallic phases in the Au-Pd wire. The Au-Cu wire also slowed down the growth rate with a different mechanism. Both wires have better reliability based on the microstructure examination. The reliability test results show longer working life at higher temperatures in comparison with the regular Au wire.
Nondestructive determination of Young’s modulus, coefficient of thermal expansion, Poisson ratio, and thickness of a thin film has long been a difficult but important issue as the film of micrometer order thick might behave differently from that in the bulk state. In this paper, we have successfully demonstrated the capability of determining all these four parameters at one time. This novel method includes use of the digital phase-shifting reflection moire´ (DPRM) technique to record the slope of wafer warpage under temperature drop condition. In the experiment, 1-um thick aluminum was sputtered on a 6-in silicon wafer. The convolution relationship between the measured data and the mechanical properties was constructed numerically using the conventional 3D finite element code. The genetic algorithm (GA) was adopted as the searching tool for search of the optimal mechanical properties of the film. It was found that the determined data for Young’s modulus (E), Coefficient of Thermal Expansion (CTE), Poisson ratio (ν), and thickness (h) of the 1.00 um thick aluminum film were 104.2Gpa, 38.0 ppm/°C, 0.38, and 0.98 um, respectively, whereas that in the bulk state were measured to be E=71.4 Gpa, CTE=23.0 ppm/°C, and ν=0.34. The significantly larger values on the Young’s modulus and the coefficient of thermal expansion determined by this method might be attributed to the smaller dislocation density due to the thin dimension and formation of the 5-nm layer of Al2O3 formed on top of the 1-um thick sputtered film. The Young’s Modulus and the Poisson ratio of this nano-scale Al2O3 film were then determined. Their values are consistent with the physical intuition of the microstructure.
Laminar heat transfer for large ranges of Reynolds numbers, rotational Reynolds numbers, and Prandtl numbers are studied numerically for incompressible fully developed flow in a circular straight pipe, which is rotating constantly about an axis perpendicular to its own axis under the constant wall temperature gradient condition. There exist four types of local Nusselt number distributions associated with the four different flow regimes for different parameters depending on the relative importance of different forces. Correlations of the averaged Nusselt number are also provided. When the Prandtl number is sufficiently large, the temperature distribution in the core is determined essentially by the secondary flow. Scaling analyses are provided for understanding the essential physics of the problem.
simultaneously determine of thermal expansion (a), Poisson ratio (v), and thickness (t) of thin films on a silicon wsifer. A digital phase-shifted reflection moirt (DPRM) technique was adopted to record the warpage slope of the fihdwafer composites under temperature change. These data were used to compare with the ANSYS analysis, and the genetic algorithm (GA) was employed to search for the optimal mechanical parameters of the films. In the first experiment, 1.20-um thick copper was sputtered on a 4-inch silicon wafer. The determined E, a, v, and t of this film were 95.9 Gpa, 38.7 ppm/"C, 0.16, and 1.13 um, respectively. The properties in the bulk state were found to be E=110 to 126 GF'a, a=16.6 to 17.6ppm/"C, and v=0.33 to 0.36 While the delermined film thickness was in good agreement with the measured value, the deviation in E, a and v was significant. The micro-structural difference between the bulk material and the thin film, and oxidation on the film surface were considered to be the two major causes to this deviation. The thickness of the oxidative layer was determined to be 326 nm wilh E=89.6GPa by considering the Cu-film as a two-layered stnicture. In order to verify the determined mechanical patameters of this 1.2-um Cu film, additional 2.4-um Cu film was sputtered on the CdSi wafer and the determined mechanical parameters of this additional Cu film were identical to the data obtained in the 1.2-um film, which demonstrated the validity of the developed method.
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