Intermetallic compound (IMC) growth during solid-state aging at 125, 150, and 170 °C up to 1500 h for four solder alloys (eutectic SnPb, Sn–3.5Ag, Sn–3.8Ag–0.7Cu, and Sn–0.7Cu) on Cu under bump metallization was investigated. The samples were reflowed before aging. During the reflow, the solders were in the molten state and the formation of the IMC Cu6Sn5 in the cases of eutectic SnPb and Sn–3.5Ag had a round scallop-type morphology, but in Sn–0.7Cu and Sn–3.8Ag–0.7Cu the scallops of Cu6Sn5 were faceted. In solid-state aging, all these scallops changed to a layered-type morphology. In addition to the layered Cu6Sn5, the IMC Cu3Sn also grew as a layer and was as thick as the Cu6Sn5. The activation energy of intermetallic growth in solid-state aging is 0.94 eV for eutectic SnPb and about 1.05 eV for the Pb-free solders. The rate of intermetallic growth in solid-state aging is about 4 orders of magnitude slower than that during reflow. Ternary phase diagrams of Sn–Pb–Cu and Sn–Ag–Cu are used to discuss the reactions. These diagrams predict the first phase of IMC formation in the wetting reaction and the other phases formed in solid-state aging. Yet, the morphological change and the large difference in growth rates between the wetting reaction and solid-state aging cannot be predicted.

The electromigration of eutectic SnPb solder interconnects between a Si chip and a FR4 substrate was studied at 120 °C for up to 324 h with current stressing of 104 amp/cm2. Hillocks were observed at the anode and voids at the cathode. The dominant diffusing species was found to be Pb, confirmed by its accumulation at the anode. Diffusion markers were used to measure the electromigration flux and calculate the effective charge of atomic diffusion in the solder. Extensive microstructural evolution was also observed in the two-phase solder alloy that occurred by a ripening process.

A series of new metal chalcogenides Ba 4 CuGa 5 Q 12 (Q = S, S 0.75 Se 0.25 , Se) were synthesized using KBr flux at 750 °C. The three compounds are isostructural and adopt the noncentrosymmetric space group P4̅ 2 1 c. Crystal data are as follows: Ba 4 CuGa 5 S 12 , 1, a = 13.040(1) Å, c = 6.304(1) Å, and Z = 2; Ba 4 CuGa 5 S 9.00(1) Se 2.92(1) , 2, a = 13.1585(2) Å, c = 6.3520(2) Å, and Z = 2; Ba 4 CuGa 5 Se 12 , 3, a = 13.598(1) Å, c = 6.527(1) Å, and Z = 2. The three-dimensional framework in 1 is constructed by infinite columns ∞ 1 [CuGa 4 S 10 ] 7− that surround the discrete GaS 4 tetrahedra situated on a 4̅ axis. The discrete GaS 4 tetrahedra on the stacking (112) planes and canted oriented edge-sharing CuS 4 tetrahedra within the columns may account for the occurrence of strong second-harmonic generation (SHG) responses. Compounds 1−3 are transparent in the mid-infrared range and have the absorption edges at 2.82, 2.05, and 1.45 eV, respectively. The new nonlinear optical (NLO) materials are type-I nonphase matching at 693 nm and display strong SHG intensities that are ∼2.7, ∼2.6, and ∼1.1 times that of AgGaSe 2 at 808 nm. Raman spectroscopic characterization of the compounds is reported.

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A versatile system has been designed and fabricated to prepare atom-probe field-ion-microscope (APFIM) specimens in a systematic manner, such that internal interfaces can be positioned in the tips of these wire specimens for subsequent analysis of their chemical composition. This system incorporates both beaker electrolytic and zone electrolytic cell configurations, a specially constructed power supply, and a special transmission electron microscope holder for wires. The power supply enables ac electroetching or dc electropolishing in the automated or manual modes. The ac wave forms available are sine (0.002 Hz–200 kHz) or square (10 Hz–20 kHz). Triggering and gating are performed manually or with a pulse generator. The dc output is gated manually to produce a continuous output or with a pulse generator to produce single pulses with widths in the range 50 μs–1 s. A counter indicates the number of periods of voltage applied, and the total charge transferred in the electrolytic cell is integrated in the range 10 μA s–1 kA s. The power supply provides 0 to ±48 V peak at 1 A peak. A double-tilt stage for an Hitachi H-700H 200 kV transmission electron microscope (TEM) was radically modified to hold APFIM specimens; this stage is vibrationless at 310 000× magnification. It has a tilting range of ±30° and ±27° for the x and y tilts, respectively. Examples are given of the controlled backpolishing of W-3 at. % Re, W-25 at. % Re, Mo-5.4 at. % Re, and Fe-3 at. % Si specimens, and their observation by TEM, to selectively place grain boundaries in the tip region. The analysis of the chemical composition of a grain boundary, which is first located in a W-25 at. % Re specimen via TEM, by the APFIM technique is presented.