Gas chromatographic studies of derivatives of celluline-like substances.
Abstract Different aspects of the gas chromatographic determination of the celluline-like substances exhibiting specific cardiotonic activity are discussed. As this substances is isolated from frog skin and bladder, many impurities have to be considered. Determination of these samples, having a broad range of boiling points, was performed by means of programmed-temperature gas chromatography. Identification of unknown peaks was executed with the help of pure standard substances and retention indices.
Contribution to the theory of the retention index system
Abstract After examining the relationship between retention index and column temperature under isothermal conditions, we have shown in a recent publication that the temperature-dependence of the retention index may generally be determined by an Antoine-type equation: After further investigation, we have established that the retention indices can be exactly calculated from programmed-temperature gas chromatography data with the following equation: A great advantage of this equation is that the data from normal hydrocarbons are not included in it.
“ 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.