| Summary: | 碩士 === 國立中央大學 === 機械工程研究所 === 91 ===
Shear strength of the ball grid array (BGA) Bi-43Sn and Sn-9Zn solder balls re-flowed on the Ni/Au-coated Cu-pads was estimated. The strength of the joint between the re-flowed solder ball and the Ni/Au-coated pad was influenced by the thickness of the Au-coating. For the Bi-43Sn soldering system, the shear strength decreased gradually with increasing the Au-coating from 0.5 to 1.2 μm, and abruptly at thickness greater than 0.1 μm. In contrast, for the Sn-9Zn soldering system, the strength increased gradually with the thickness of the Au-coating.
The electrolytic migration of some tin-based binary solder (i.e., Sn-Ag, Sn-Bi, Sn-Cu, Sn-In, Sn-Pb and Sn-Zn alloy) was explored in various solutions (e.g., de-ionized water, 0.01M (NH4)2SO4, 0.01M NaCl and aqueous flux solution -containing 2.2 mM chloride ion) at a dc-bias of 5V. The Sn-Ag and Sn-Pb systems were susceptible to electrolytic migration in de-ionized water but immune to migration in 0.01 M (NH4)2SO4 solution. All the binary systems in this work were facilitated to migration in the chloride solution.
Potentiodynamic and potentiostatic polarization for various soldering systems were compared. X-ray photoelectron spectroscopy (XPS) of the corrosion products on the anode and the dendrites across the electrode were examined. The results from the electrochemical polarization and the XPS analyses were helpful in elucidation of the distinction on migration behavior of various soldering systems.
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