A technology for the fabrication of movable LIGA-Microstructures by molding was developed, which enables the cheaper production of e.g. LIGA-Acceleration Sensors [1]. For this purpose an aligned molding process had to be developed. The realized experimental setup consists of two subsystems, the molding machine and the alignment arrangement [2]. After aligning a substrate it is transported into the molding machine. An effective and extremely precise dimension translation system is required. Although during modling temperature changes appear and high forces are applied, the dimension stability during the molding process has to be guaranteed. The presented system and setup deals successfully with these conditions. An alignment quality of ± 10 μm is realized. Using the aligned molding technology temperature compensated LIGA-acceleration sensors [1] were fabricated. The proper function of the sensors was demonstrated.

The prelims comprise: The Basic Concepts of the LIGA Technique Modifications and Extensions of the LIGA Technique Microstructures in the LIGA Technique The Microspectrometer in the LIGA Technique The Acceleration Sensor in the LIGA Technique Micropump Manufactured by Thermoplastic Molding Optochemical Sensor Systems for Detection of Toxic Substances in Gases and Liquids Electrochemical Microanalytical System (ELMAS) for the Ionometry of Liquid Media Concepts for Miniaturized Analytical Microprobes: Integrated Optical NIR Evanescent Wave Sensor System for Chemical Analysis Near Field Thermal Lens System Chemical Microanalyzer Systems: Their Role and Importance in Modern Chemical Analysis in Environmental Workplace and Process Control and Medical Diagnosis: a Résumé References

For the past few years capacitive LIGA acceleration sensors have been fabricated at the Karlsruhe Nuclear Research Center. The advantages of LIGA acceleration sensors are their high zero-acceleration capacitance of 5 pF, temperature-compensated design with low offset temperature coefficient (TCO=1.5x10(-4) FSO K-1) and high linearity. In addition, a high-precision readout circuit has been developed. The electronic circuit's distinguishing feature is its extremely low noise, so that capacitance changes of 5 aF Hz-(1/2) can be detected. Combined with a 1g LIGA acceleration sensor, a resolution of 1 mu g Hz-(1/2) has been achieved. A feedback system has been developed for a further improvement of linearity. The electronic circuit has been realized as a multichip module (MCM) in multilayer thick-film technique on a 10 mm x 20 mm Al2O3 substrate. The final result is a sensor system with excellent properties as regards temperature behaviour, dynamic range and resolution.

Combination of the LIGA process with a sacrificial layer technique offers the possibility of fabricating in one process sequence metal capacitive acceleration sensors with a movable seismic mass and stationary electrodes on top of the same substrate. The process allows micromechanical devices with a free geometry to be designed. Use has been made of this advantage to fabricate extremely temperature-resistant acceleration sensors. Temperature resistance is achieved by designing the sensor partly with a positive and partly with a negative temperature coefficient. The design presented here is for a 1 g sensor with a measured temperature coefficient of offset (TCO) of 1.02×10−4g/K in the temperature range −10-100 °C.

The LIGA process has several advantages such as free cross-sectional shaping and realization of great structural height in combination with small lateral dimensions. By this technique the micromechanical elements are made out of metal. In contrast to silicon, metal shows aging effects. As the micromechanical elements are normally deformed and therefore exposed to stress during activation it is of great interest to know the long term behaviour of these micromechanical LIGA elements. An experimental set-up is described to determine the fatigue curves (S-N curves) for micromechanical elements made of electroplated nickel using electromagnetic activation. Also experimental results are presented.