Flexible Packaging by Film Assisted Molding for Microintegration of Inertia Sensors.

Packaging represents an important part in the microintegration of sensors based on microelectromechanical system (MEMS). Besides miniaturization and integration density, functionality and reliability in combination with flexibility in packaging design at moderate costs and consequently high-mix, low-volume production are the main requirements for future solutions in packaging. This study investigates possibilities employing printed circuit board (PCB-)based assemblies to provide high flexibility for circuit designs together with film assisted transfer molding (FAM) to package sensors. The feasibility of FAM in combination with PCB and MEMS as a packaging technology for highly sensitive inertia sensors is being demonstrated. The results prove the technology to be a viable method for damage-free packaging of stress- and pressure-sensitive MEMS.

Nonorthogonal Dilithium-1,3-biborataallenes Containing Planar-Tetracoordinate Carbon Atoms.

Deviations of up to 36° from the orthogonality of the planes of the terminal B atoms of the allene skeleton and their neighbors (ipso-C atoms) are observed in tetraaryl-1,3-diborataallenes of contact-ion triples 1. The unusual geometries are caused by steric hindrance between ortho-methyl groups, which is induced by interactions of the lithium counterions with the π electrons of the aryl substituents, as well as by small barriers to planarization of 1,3-diborataallenes. Ar=for example, 2,3,5,6-tetramethylphenyl.

Why do two π-electron four-membered Hückel rings pucker?

Notwithstanding their two (i.e., 4n + 2) π electrons, four-membered ring systems, 1-4, favor puckered geometries (1a-4a) despite the reduction in vicinal π overlap and in the ring atom bond angles. This nonplanar preference is due to σ → π* hyperconjugative interactions across the ring (A) rather than to partial 1,3-bonding (B). Electronegative substituents (e.g., F in C(4)F(4)(2+)) reduce the σ → π* electron delocalization, and planar geometries result. In contrast, electropositive groups (e.g., SiH(3) in C(4)(SiH(3))(4)(2+)) enhance hyperconjugation and increase the ring inversion barriers substantially.

Indirect nuclear spin-spin coupling constants in 1,2-diboretane-3-ylidene, a homoaromatic system with pi and sigma 3c/2e bonds. Comparison of experimental data with calculations using density functional theory (DFT).

The non-classical 1,2-diboretane-3-ylidene 1a was studied by 13C and 29Si NMR spectroscopy in order to obtain coupling constants 1J(13C,11B) and 1J(29Si,13C). The magnitudes of 1J(13C,11B) were deduced from linewidth measurements in low-temperature 13C and 11B NMR spectra. Calculation of the coupling constants for model compounds related to 1a, using DFT methods based on optimized geometries [B3LYP/6-311+G(d,p)], gave data in agreement with the experiments. Furthermore, the calculations predict for the first time a negative sign of 1J(13C,11B) which mirrors the bonding situation in 1 as described by theory.