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Notes: Purpose - To study the behaviour of voids in PBGA solder joints and their influence on the lifetime of lead-free solder joints. Design/methodology/approach - The behaviour of voids was studied using micro via and land pad PWBs, PBGA components, and by measuring voids in the solder joints. The lifetimes of solder joints were tested using accelerated temperature tests. Findings - Number of factors affecting the solder joint lifetimes were found. The voids were discovered to have a significantly large influence on the solder joints. Practical implications - The findings can be used to achieve better soldering results, methods, and designs. Originality/value - In this paper, the effect and the behaviour of voids were studied profoundly. The findings can be valuable to researchers and process personnel.

Notes: Purpose - To provide further knowledge of the effect of solder composition and PCB surface finish on the creep properties of lead-free SnAgCu solder joints. Design/methodology/approach - Single-overlap shear specimens were prepared for the creep testing. The test matrix included three different SnAgCu pastes with hypoeutectic, eutectic, and hypereutectic compositions. An Sn63Pb37 solder paste was used as a reference. The PCB finishes used were NiAu, organic solderability preservative (OSP) and immersion tin. The creep tests were performed at 85 and 105°C using a dead-weight system. Findings - According to the results, the SnAgCu solder with eutectic or near-eutectic composition is the safest choice when the creep behaviour of solder joints is considered. Of the three different PCB surface finishes, immersion tin is the most favourable choice for use with SnAgCu joints when creep is the predominant deformation mechanism in the joints. On the NiAu finish the creep properties of SnAgCu solder joints were significantly weaker in eutectic and hypereutectic SnAgCu joints than on Sn and OSP. Originality/value - The results can be used to enhance the reliability of SnAgCu joints in demanding conditions, when special attention is paid to the choice of PCB surface finish and SnAgCu solder composition.

Notes: Abstract Calculations were carried out within the Landau Vlasov model formalism, using an effective force which has an adjustable isospin dependent term. We showed that the strength of this term is influencing the dynamics of heavy-ions collisions; at relatively high energy, nuclear preequilibrium fluxes are sensitive to the isospin strength.

Notes: Abstract The Polaris deposit is one of the largest Mississippi Valley-type deposits in the world, with 22 million tonnes of ore at 14% Zn and 4% Pb contained in a single, compact orebody surrounded by dolomitized host rocks. Using detailed sampling of carbonates in the orebody and the dolostone halo, this paper aims to characterize the temporal and spatial evolution of the mineralizing system, and to understand the mechanisms that controlled the accumulation of this large, compact Zn–Pb deposit. Five types of dolomite have been distinguished, including three replacement (RD) and two pore-filling dolomites (PD). The paragenetic order is RD1, RD2, RD3, PD1, and PD2. Pore-filling calcite (PC) postdates all other minerals. In most cases, sulfides and dolomite did not co-precipitate, but sphalerite and galena largely overlap with RD3 and PD1. Various dolomites are dissolved or replaced by sulfide-precipitating fluids; sulfides in turn can be overgrown by dolomites. Colloform texture in sphalerite is widespread. Fluid inclusions were studied in RD3, PD1, PD2, sphalerite, and PC. The overall ranges of homogenization temperatures (T h) and last ice-melting temperatures (T m-ice) for fluid inclusions in dolomites and sphalerite are from 67 to 141 °C and from −46.7 to −27.0 °C, respectively, consistent with warm basinal brines with high salinities and Ca/Na ratios. Gas chromatographic analysis of these fluid inclusions indicates low concentrations of hydrocarbons (〈0.06 mol%). C, O, and Sr isotopes were analyzed for all dolomites and PC, as well as for the fine-grained host limestone and early diagenetic calcite (SC–RC). The isotopic values of RD2, RD3, PD1, and PD2 cluster tightly and form largely overlapping domains. With respect to the host limestone, they are depleted in 18O, similar in δ13C, and slightly enriched in 87Sr. There are no regular spatial variations for fluid inclusion and isotope data, indicating an overall geochemical homogeneity in the hydrothermal system. However, certain samples close to the fracture zones in the orebody with slightly elevated T h and 87Sr/86Sr values and depleted δ18O values suggest that the fracture zone was the conduit for the hot brines. Based on the geological and geochemical characteristics of the deposit, we propose that sulfide precipitation at Polaris was caused by mixing of a reduced, metal-rich, sulfur-poor fluid with a reduced, metal-poor, sulfur-rich fluid at the site of mineralization. The metal-carrying fluid ascended along fractures from below the deposit and was hotter than the host rocks, whereas the reduced sulfur-carrying fluid was delivered to the site of mineralization laterally and was in thermal equilibrium with the host rocks. This model can readily explain the dissolution of dolomite during sulfide precipitation and the abundance of colloform sphalerite, as well as the low concentrations of hydrocarbons in fluid inclusions.

Notes: Abstract Using the path integral formalism and a model based on statistical arguments, we derive the correlation function which enters the description of a one-dimensional collective system coupled to an intrinsic system in terms of transport concepts. The derivation shows a finite time dependence of the correlation function in contradistinction to a former calculation. We discuss some points related to the derivation and estimate the relaxation times which characterise the memory effects in both cases of weak and strong coupling.