Horst Theuss

A Bulk Acoustic Wave (BAW) Based Transceiver for an In-Tire-Pressure Monitoring Sensor Node

Attaching a tire pressure monitoring system (TPMS) on the inner liner of a tire allows sensing of important additional technical parameters, such as vehicle load or tire wearout. The maximum weight of the sensor is limited to 5 grams including package, power supply, and antenna. Robustness is required against extreme levels of acceleration. The node size is limited to about 1 cm3 to avoid high force-gradients due to device-deformation and finally, a long power supply lifetime must be achieved. In this paper a low-power FSK transceiver is presented. Exploiting BAW resonators the use of a bulky and shock-sensitive crystal and a PLL can be avoided. This makes the system more robust and radically reduces the start-up time to 2 ¿s from few ms as in state-of-the-art crystal oscillator based systems. The current consumption of the transceiver is 6 mA in transmit mode with a transmit output power of 1 dBm and 8 mA in receive mode with a sensitivity of -90 dBm at a data rate of 50 kBit/s and a bit error rate of 10-2. The transceiver ASIC and a microcontroller ASIC, a MEMS sensor, and a BAW die are arranged in a 3-D chip stack for best compactness, lowest volume, and highest robustness. The sensor node allows sensing of pressure, acceleration, supply voltage and temperature.

A robust wireless sensor node for in-tire-pressure monitoring

State-of-the-art tire pressure monitoring systems (TPMS) are wireless sensor nodes mounted on the rim. Attaching the node on the inner liner of a tire allows sensing of additional technical parameters, such as road condition, tire wearout, temperature, tire friction, side slip, wheel speed, and vehicle load. They may be used for improved tracking and engine control, feedback to the power train and car-to-car communication purposes.

Integration of polymer bonded magnets into magnetic sensors

This paper introduces a novel assembly and manufacturing technology for integrating permanent magnets into magnet sensor modules by use of plastic bonded magnets. High precision speed sensors in automotive applications, e.g. in anti-blocking-system or engine management, are based on a magnetic measurement principle [1]. Typical sensor modules contain a semiconductor based sensor chip and a permanent magnet providing the necessary bias field (see Fig. 1). This field is modulated by a passing external gear wheel out of material with high magnetic permeability, which is part of the magnetic circuit. The wheel speed can directly be determined by measuring the frequency of the magnetic field modulation. Permanent magnets are often assembled in a sequential pick and place process. We report a novel assembly technology by direct molding of thermoplast bonded magnets onto a chip carrier containing pre-assembled sensors. We will show, that this offers the following advantages: - Highest accuracy - Optimum working point, in particular for GMR sensors - High throughput by efficient parallel process - Simplification of the module assembly.

3D Integration of MEMS

This chapter elaborates on packaging technologies for MEMS. Within a basic concept discussion, we focus on cavity formation and on further assembly of the MEMS to produce a surface mountable device. We discuss standard solutions as well as examples for complex three-dimensional (3D) heterogeneous integration. Emphasis is also put on the importance of low stress packaging: