The methanol oxidation on a hydroxylated Pt (Pt(111)-OH) surface has been investigated by means of infrared reflection absorption spectroscopy (IRAS) in ultra-high vacuum (UHV) and in acidic solution. The Pt(111)-OH surface in UHV was prepared by introducing water molecules on a Pt(111)-(2 x 2)-O surface and annealed at temperature higher than 160 K. Methanol was then, introduced to the Pt(111)-OH surface to show the dependence of the reaction intermediate on the annealing temperature. At an annealing temperature below 160 K, IR bands assignable to methanol overlayer were observed and no detectable intermediates, such as CO, formaldehyde and formate, were formed, suggesting that methanol molecules remain stable on Pt(111) surface without dissociation at this temperature region. At an annealing temperature above 160 K, on the other hand, CO and formate were observed. In addition, the oxidation of CO on Pt(111)-OH showed no sign of formate formation, indicating that formate is not derived from CO, but from a direct oxidation of methanol. Methanol oxidation was carried out in 0.1 mol dm(-3) HClO(4) solution on Pt(111) with a flow cell configuration and showed the formation of formate. These results indicate that the formate is the dominant non-CO intermediate both in UHV and in acidic solution, and the preadsorbed oxygen-containing species, in particular OH adsorbates, on Pt(111) surface plays a very important role in the formate formation process in methanol oxidation reaction.

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The aim of this study is to investigate the joint properties of Sn-58mass%Bi and Sn-57mass%Bi-0.5mass%Sb low-melting lead-free solder balls on the electroless Ni/Au and Ni/Pd/Au plated Cu electrodes fabricated with a lead-free plating solution. Compared with the conventional Ni plating solution containing lead, the soldered joints with Ni/Au and Ni/Pd/Au electrodes fabricated with the lead-free plating solution showed comparable joint properties. In the joints with Ni/Pd/Au electrodes, ball shear force increased when the Pd layer is dissolved into solder by multi reflows. In both joints with Ni/Au and Ni/Pd/Au electrodes, a part of the Ni layer was dissolved into solder and thus the (Ni,Cu)3Sn4 intermetallic compound layer formed at the joint interface. Ball shear force decreased upon aging due to the growth of the (Ni,Cu)3Sn4 layer at the joint interface.

An electroless Ni/Pd/Au plated electrode is expected to be used as an electrode material for lead-free solder to improve joint reliability. The aim of this study is to investigate the effect of the thickness of the Pd layer on joint properties of the lead-free solder joint with the electroless Ni/Pd/Au plated electrode. Solder ball joints were fabricated with Sn-3Ag-0.5Cu (mass%) lead-free solder balls and electroless Ni/Pd/Au and Ni/Au plated electrodes. Ball shear force and microstructure of the joint were investigated. The (Cu,Ni)6Sn5 reaction layer formed in the joint interface in all specimens. The thickness of the reaction layer decreased with increasing the thickness of the Pd layer. In the joint with a Pd layer 0.36 μm thick, the remained Pd layer was observed in the joint interface. In the joint, impact shear force decreased compared with that of the joint without the remained Pd layer. On the contrary, when the thickness of the Pd layer was less than 0.36 μm, the Pd layer was not remained in the joint interface and impact shear force improved. Impact shear force of the joint with the electroless Ni/Pd/Au plated electrode was higher than that with the electroless Ni/Au one.

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