The crystal structure of auramine perchlorate: correlation of the results with specular reflection spectroscopy.
The x-ray analysis of auramine perchlorate has been performed in order to establish the orientation of the cationic chromophoric group in the crystal for comparison with the orientation that was proposed on the basis of specular reflection studies. The compound crystallizes with two molecules per unit cell in space group P1 and cell parameters a = 8.86 A, b = 9.69 A, c = 11.27 A, alpha = 97 degrees 40', beta = 99 degrees 34', and gamma = 106 degrees 16'. The orientation of the chromophore is in good agreement with the crystal model. Other features of the structure are the hydrogen bonding scheme of the perchlorate ion, the highly distorted chromophoric group, and the planar dimethylamine substituents.
Structural Features from Reflection Spectra: Orientation of 1, 3,-bis-(Dimethylamino) trimethinium Perchlorate Molecules in the Crystal
Abstract If the orientation of a molecular electronic transition moment with respect to the molecular framework is known, reflection spectra of crystalline samples on various faces may be used to locate the molecules in question. This can be done through projection of the transition moment on the faces, or through use of the optical indicatrix. The two methods are briefly compared, and the preferred indicatrix method is applied to crystals of the dye 1,3-bis-(dim-ethylamino)trimethinium perchlorate. Along each principal axis of the indicatrix, best fit values for reasonant frequency, plasma frequency, and damping constant are obtained in the frequency range of the first singlet. Parameters of the crystal structure having to do with the orientation of the dye molecules are then deduced from this information.
“ 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.