No abstract

The cross-interaction of the under-bump metallurgy (UBM)/solder interface and the solder/surface-finish interface in flip-chip solder joints was investigated. In this study, the UBM on the chip side was a single layer of Cu (8.5 µm), and the surface finish on the substrate side was a 0.2-µm Au layer over 5-µm Ni. It was shown that, after two reflows, the Ni layer of the surface finish had been covered with (Cu 1Ϫx Ni x ) 6 Sn 5 . This shows that the effect of cross-interaction of the two interfaces is important even during the reflow stage. During subsequent solidstate aging at 115°C, 135°C, and 155°C, the formation of (Cu 1Ϫx Ni x ) 6 Sn 5 over the Ni layer was found to have the effect of reducing the Ni consumption rate. At the same time, the Cu consumption rate of the UBM was accelerated. The results of this study show that the selection of the UBM and the surface finish has to be considered together because the cross-interaction of the two interfaces plays an important role.

Ordered periodic mesoporous organosilicas containing different fractions of benzene groups in the silica framework, based on the cubic SBA-1 mesostructure (Pm3 j n mesophase), were synthesized with the directsynthesis route via co-condensation of tetraethoxysilane (TEOS) and 1,4-bis(triethoxysilyl)benzene (BTEB) under acidic conditions using cetyltriethylammonium bromide as a structure-directing agent. A significantly large amount of TEOS, up to 70 mol % based on silica, can be incorporated into the silica wall without degrading the structural integrity of the materials. By optimization of the synthesis compositions, the resulting materials exhibited much higher surface areas (up to 1210 m 2 /g) and larger pore volumes (up to 0.64 cm 3 /g) as compared to the previous analogue, which only exhibited a surface area of 381 m 2 /g and a pore volume of 0.11 cm 3 /g. Two-dimensional (2D) 29 Si{ 1 H} heteronuclear correlation (HETCOR) NMR spectra, acquired as a function of contact time, provided direct spectroscopic evidence that a single mesophase with various Q (from TEOS) and T silicon species (from BTEB) located randomly within the pore walls via co-condensation of BTEB and TEOS at a molecular level. Such information is often not achievable by other characterization techniques. The 1 H-29 Si distance information between phenylene protons and nearby T 3 silicon atoms obtained from density functional theory calculations is also in good agreement with the observations of 2D 29 Si{ 1 H} HETCOR NMR experiments.