The Determination of Inorganic Sulphate in Sodium Lauryl Sulphate
The official method for the determination of inorganic sulphate in sodium lauryl sulphate is time‐consuming. Separation of organic and inorganic sulphate via the lead salts followed by complexometry leads to a rapid and convenient method with readily reproducible results.
Complexometric Determination of Sulfate
A simple and rapid method for the determination of sulfate in materials obtained during extraction of uranium from ores is based on precipitation as lead sulfate from acid solution containing isopropyl alcohol. The precipitate is filtered and redissolved in an excess of measured standard (ethylenedinitrilo)tetraacetic acid (EDTA) solution. The excess of the latter is then backtitrated with a standard zinc chioride solution and Eriochrome Black T as indicator. A detailed study of the optimum conditions for the precipitation of lead suifate has been carried out, and the degrees of interference of phosphate, arsenate, iron, and uranium ions have been tested. The method is virtually free of interferences and gives accurate results in the range 0.1 to 100% sulfates the time required for a determination is about 30 to 45 minutes. (auth)
“ PARTIALLY-ACTIVATED ” FLUX RESIDUE IMPACTS ON ELECTRONIC ASSEMBLY RELIABILITIES
The reliabilities of the flux residue of electronic assemblies and semiconductor packages are attracting more and more attention with the adoption of no-clean fluxes by majority of the industry. In recent years, the concern of “partiallyactivated” flux residue and their influence on reliability have been significantly raised due to the miniaturization along with high density design trend, selective soldering process adoption, and the expanded use of pallets in wave soldering process. When flux residue becomes trapped under low stand-off devices, pallets or unsoldered areas (e.g. selective process), it may contain unevaporated solvent, “live” activators and metal complex intermediates with different chemical composition and concentration levels depending on the thermal profiles. These partially-activated residues can directly impact the corrosion, surface insulation and electrochemical migration of the final assembly. In this study, a few application tests were developed internally to understand this issue. Two traditional liquid flux and two newly developed fluxes were selected to build up the basic models. The preliminary results also provide a scientific approach to design highly reliable products with the goal to minimize the reliability risk for the complex PCB designs and assembly processes.