The tilt sensor is a novel approach to theft warning for cars. The tilt sensor measures its inclination to the horizontal when the vehicle is parked and stores it in memory. An attempt at theft is likely to disturb that inclination. While the vehicle remains at rest, the sensor detects any deviation from the stored inclination that exceeds a predetermined value. It then triggers an appropriate warning response by the antitheft electronics system in the vehicle.

HL-Planartechnik GmbH (Dortmund, Germany) manufactures tilt sensors for various carmakers. A tilt sensor consists of a hermetically sealed ceramic housing with a thin-film sensor substrate on its bottom surface. The housing is filled with a conductive fluid. Measurement electrodes and contacts are mounted on the sensor substrate, which is bonded to the ceramic housing with a solder glass joint. Solder glass is a paste that has the structure and characteristics of glass—transparent and gas-proof—when it is cured.

The tilt sensors are assembled on an automated production line designed and built by Sieghard Schiller GmbH & Co. KG (Sonnenb¿hl, Germany). The line includes processes for joining thick-film substrate to the ceramic housing, dispensing the solder glass, precision metering of the sensing liquid, installation and soldering of pins, in-line cleaning, encapsulation and packaging.

At the first station, the ceramic housings are supplied stacked in pallets, and the thick-film substrates are fed from stack magazines. Before the substrates are joined to the housings, the components are visually inspected for dimensional accuracy. At the second station, solder glass is dispensed to seal the thick-film substrate against the ceramic housing.

After the solder glass is cured in the oven, conductive fluid is metered into the housing at the next station, and the opening is then immediately soldered shut. To establish contact between the thick-film substrate and the outside world, pins are attached to the substrate and immediately soldered using a hot-bar soldering process. Any external contamination is removed by an in-line cleaning and drying system. Finally, the device is encapsulated with insulation.

To ensure reliable sensors are being produced, the quality of each individual process is continually monitored throughout the assembly process. For example, a test scale and cyclic metered doses are used to verify the correct amount of encapsulant, and inspection tasks are undertaken using high-performance imaging systems. Defective modules are removed from the process when they are first detected. This ensures that every module packaged at the end of the production line is acceptable.

For more information about automated assembly systems, call 770-371-5042 or visit