Reduction of Thermomechanical Stress Using Electrically Conductive Adhesives

We compare the thermomechanical stresses in solar cell interconnections based on electrically conductive adhesives (ECA) with soldered joints by using bending experiments and finite element analysis (FEA). Additionally, the influence of an increasing number of busbars is studied. The FEA is validated by measuring the bending of cell strips after cooling down from a single-sided interconnection process. The material parameters are determined by tensile tests, microscopy and nanoindentation. The comparison of ECA and soldering shows that an elastomer with a Young's modulus of below 0.5 GPa is capable of reducing the thermomechanical stress effectively resulting in, approximately, a mean tensile stress in the ECA of 5 MPa, 110 MPa in the ribbon, and a maximum compressive stress in the silicon of 75 MPa. Increasing the number of busbars from three to five leads to a reduction in compressive stresses in the silicon and a slight increase of the peak tensile stress in the busbars

Improved Microtransformer Design Utilizing Fe-Co Magnetic Core

This paper presents the design, fabrication, and characterization of on silicon integrated micro-transformers for high frequency power applications. This device has stable characteristic of L versus f up to frequencies higher as 50 MHz. The design is improved, so that the electrical resistance of coils is reduced and current capability is increased. The microtransformer shows an inductivity of about 50 nH, resistance of 350 mΩ and can be applied for current up to 1.5 A

Recent Developments of Magnetoresistive Sensors for Industrial Applications

The research and development in the field of magnetoresistive sensors has played an important role in the last few decades. Here, the authors give an introduction to the fundamentals of the anisotropic magnetoresistive (AMR) and the giant magnetoresistive (GMR) effect as well as an overview of various types of sensors in industrial applications. In addition, the authors present their recent work in this field, ranging from sensor systems fabricated on traditional substrate materials like silicon (Si), over new fabrication techniques for magnetoresistive sensors on flexible substrates for special applications, e.g., a flexible write head for component integrated data storage, micro-stamping of sensors on arbitrary surfaces or three dimensional sensing under extreme conditions (restricted mounting space in motor air gap, high temperatures during geothermal drilling).DFG/CRC/653German Federal Ministry of Education and Researc

Direct hot embossing of microelements by means of photostructurable polyimide

While automatic hot embossing systems are available for large- and small-scale productions of polymeric devices, one of the process challenges remains to be the manufacturing of precise, durable, and yet inexpensive hot embossing stamps. The use of metallic stamps manufactured by electroplating a photoresist pattern or by precision milling and their replication into silicone molds with UV-lithography, electroplating, and molding techniques is state of the art. Yet, there have been few, if any, thriving attempts to directly emboss polymers by means of bare photoresists, and in particular polyimide-based photoresists, without transferring the photoresist patterns into a different stamp material. We conduct a proof-of-concept by developing hot embossing stamps based on photosensitive polyimide. We focus primarily on the reliability of the aforementioned stamps throughout the hot embossing cycle and the fidelity of pattern transfer onto polymeric films for different microstructural patterns. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).DFG/CRC/Planar Optronic System

Flexible Magnetic Writing / Reading System: Polyimide Film as Flexible Substrate

In the frame work of Collaborative Research Center (CRC) 653, magnetic data storage on surfaces of components has been developed. The principle is based on magnetic data storage of hard disk drives. Rigid magnetic writing heads successfully developed so far still have limited capabilities; they cannot be adapted to rough or curved surfaces and cannot withstand high mechanical shock. To overcome such drawbacks, a new design of a writing head based on a flexible substrate is proposed. This publication focuses on an investigation of a material which serves as a required substrate for this application. Baseline examinations for asserting compatibility of the flexible substrate to production processes for microelectromechanical systems (MEMS) are presented. Successfully fabricated micro structures using simple fabrication techniques based on photolithography and thin film processes are demonstrated as well. Obtained results through this work indicate that the polyimide film, namely Kapton film, is suitable as the flexible substrate for the flexible magnetic writing / reading system

Flexible Magnetic Reading/Writing System: Heat-assisted Magnetic Recording

Data storage is one of indispensable technical assets defined in a frame work of Industry 4.0. Among many data storage technologies, inherent magnetic data storage on surfaces of technical components is promising, especially when the components are employed in harsh environments. Comparing with other storage technologies like labels, RFID tags and engraving, the inherent magnetic storage is rewritable and resistant to weathering. High temperature and a high magnetic field, however, can degrade or even delete magnetically stored data. This limitation can be coped with using a medium with higher coercivity that can withstand external magnetic fields and high temperature. As a consequence of higher coercivity, a higher write field is required to magnetize the medium. A design of a flexible write head that is suitable for storage applications on surfaces of technical components, is restricted by head-medium interface criterions, and hence field strength generated from the write head cannot be arbitrary large. To solve this problem, a heat-assisted magnetic recording (HAMR) is proposed as a means to temporarily reduce coercivity of a medium during writing. A realization of a HAMR module and an experiment as well as its positive results are presented in this work