Slender Tactile Sensor for Contour and Roughness Measurements Within Deep and Narrow Holes

A tactile cantilever sensor is described which was designed for quality assurance of high-aspect ratio microcomponents, e.g., spray holes of diesel injector nozzles. It was constructed as an extremely slender silicon cantilever of 1.5-5 mm in length, 30-200 mum in width, and 25-50 mum in height comprising a silicon probing tip at its free end. Close to its clamping, a piezoresistive strain gauge was integrated for signal read-out. The novel sensor was designed to be operated at high scanning speeds offering a millimeter scanning range at a micrometer lateral resolution and a ten nanometers vertical resolution. Cross sensitivity versus temperature and ambient light referred to vertical tip deflection was below 10 nm during a tactile measurement, which was performed under typical tactile probing conditions, i.e., temperature and light intensity variations of 1 K and 0.1 mW/cm ², respectively. In form and roughness measurements with calibrated standard artifacts as well as with narrow spray holes of advanced diesel injector nozzles, we demonstrated the potential of slender cantilever sensors for high-aspect-ratio micrometrology.