Improved Mounting of Strain Sensors by Reactive Bonding.

Aim of this work is to improve the bond between a strain sensor and a device on which the strain shall be determined. As strain sensor, a CMOS-integrated chip featuring piezoresistive sensor elements was used which is capable of wireless energy and data transmission. The sensor chip was mounted on a standardized tensile test specimen of stainless steel by a bonding process using reactive multilayer systems (RMS). RMS provide a well-defined amount of heat within a very short reaction time of a few milliseconds and are placed in-between two bonding partners. RMS were combined with layers of solder which melt during the bonding process. Epoxy adhesive films were used as a reference bonding process. Under mechanical tensile loading, the sensor bonded with RMS shows a linear strain sensitivity in the whole range of tested forces whereas the adhesive-bonded sensor has slightly nonlinear behavior for low forces. Compared to the adhesive-bonded chips, the sensitivity of the reactively bonded chips is increased by a factor of about 2.5. This indicates a stronger mechanical coupling by reactive bonding as compared to adhesive bonding.

Channel model for InSb-based superresolution optical disc system.

A signal model of a superresolution optical channel would be an efficient tool for developing components of an associated high-density optical disc system. While the behavior of the laser diode, aperture, lens, and detector is properly described, a general mathematical model of the superresolution disc itself is not yet available. However, different approaches have been made to describe the properties of a mask layer, mainly based on temperature- or power-dependent nonlinear effects. The main problem of the modeling is that temperature-dependent material properties, such as thermal conductivity and refractive indices, are not known or not accurate enough to allow quantitative predictions. Therefore, it could be useful to define a signal-based or phenomenological model that can be calibrated with experimental data. In this contribution, we developed a complete optical channel model--from non-return-to-zero inverted (NRZI) input to disc readout signal--including the reflectivity of a superresolution disc with InSb used for the mask layer. Model parameters are derived from data measured using a static tester. The model is finally applied to a configuration appropriate for a dynamic superresolution optical drive by moving the focused spot relative to the material.