Fluxes and Cleaning

Flux and Cleaning Issues Related to Lead-Free Soldering... 

The rework process should not be overlooked in planning a flux and cleaning strategy. Compared to the automated processes that proceed it, it is typical to use a more aggressive flux and more of it to do rework. Use of a halide-free flux or proper cleaning after rework is essential to prevent cleanhness-related reliability problems. 

Gum Naval Stores. Turpentine and Rosin From Pine Resin Appendix 2. Quality Criteria Specifications and Test Methods, retrieved May 4, 2003 (http //www.fao.org/docrep/v6460e0b.htm) Klein Wassink, R.J. Soldering in Electronics Electrochemical Publications Isle of Man, 1989. Johnson, R.W. ELEC 6740 Electronics manufacturing Chap. 13. Flux and cleaning. johnson ... 

Hexafluorozirconic acid is used ia metal finishing and cleaning of metal surfaces, whereas the fluorozirconates are used in the manufacture of abrasive grinding wheels, in aluminum metallurgy, ceramics industry, glass manufacturing, in electrolytic cells, in the preparation of fluxes, and as a fire retardant (see Abrasives Metal surface treati nts). 

Flux response to concentration, cross flow or shear rate, pressure, and temperature should be determined for the allowable plant excursions. Fouling must be quantified and cleaning procedures proven. The final design flux should reflect long-range variables such as feed-composition changes, reduction of membrane performance, long-term compaction, new foulants, and viscosity shifts. 

Welds on steelwork need special attention because of the different composition of weld metal and adjacent steelwork, the rough surface and spatter caused by welding and the presence of welding flux. The latter is often alkaline and destructive to many paints. It is necessary to clean thoroughly, preferably by reblasting for 25-50 mm each side of the weld, fare the rough metal and wash off residual flux. The cleaned surface should then be stripe coated with the primer used on the remainder of the surface. 

Rusty pipe should not be used. The rust and loosened mill scale will travel around the circuit to block the suction strainer and the drier. Other avoidable debris are loose pieces of weld, flux, and the short stubs of welding rod often used as temporary spacers for butt welds. Pipe should only be cut with a gas torch if all the oxidized metal can be cleaned out again before closing the pipe. 

Slug/semi-annular flow. Here both slug and semi-annular flows were present. The vapor velocity increased with the heat flux and the rear of elongated bubbles began to break up (Fig. 2.30d). Coalescence was no longer clean and created a churn-like zone where the liquid slug had been. 

The objective of the present study is to develop a cross-flow filtration module operated under low transmembrane pressure drop that can result in high permeate flux, and also to demonstrate the efficient use of such a module to continuously separate wax from ultrafine iron catalyst particles from simulated FTS catalyst/ wax slurry products from an SBCR pilot plant unit. An important goal of this research was to monitor and record cross-flow flux measurements over a longterm time-on-stream (TOS) period (500+ h). Two types (active and passive) of permeate flux maintenance procedures were developed and tested during this study. Depending on the efficiency of different flux maintenance or filter media cleaning procedures employed over the long-term test to stabilize the flux over time, the most efficient procedure can be selected for further development and cost optimization. The effect of mono-olefins and aliphatic alcohols on permeate flux and on the efficiency of the filter membrane for catalyst/wax separation was also studied. 

Equation 6.12 relates CP to flux (/) and the effective mass-transfer coefficient (kes) for retained solute. For a clean membrane keff = k, which is the boundary layer mass-transfer coefficient from Sherwood correlations [45, 46], However, for a membrane... 

Electron-Transfer Reduction of 02. Within aqueous solutions the most direct means to the electron-transfer reduction of dioxygen is by pulse radiolysis. Irradiation of an aqueous solution by an electron beam yields (almost instantly 10-12 s) solvated electrons [e (aq)], hydrogen atoms (H-), and hydroxyl radicals (HO-)- If the solution contains a large excess of sodium formate [Na+ 0(0)CH] and is saturated with 02, then the radiolytic electron flux efficiently and cleanly reduces 02 to superoxide ion (O ) 21-25... 

Polished nickel or cobalt plates were mounted in cylindrical graphite forms (11 mm inner diameter), rapidly heated up to about 450 °C and then filled with a molten flux (-475 °C) consisting of the eutectic mixture 82 mass % ZnCl2 - 18 mass % NaCl. After 60 s holding the plates under the flux for cleaning their surfaces from possible contamination, the forms... 

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