Surface profilometry of high aspect ratio features

Three-dimensional surface profilometry of microscale features such as high aspect ratio holes, pins, channels, gears, threads and more complex geometries such as free form, convex and concave shapes remain challenging metrology problems. Existing profilometers are designed to measure easy accessible surfaces with macroscale dimensions, while microscale features are usually assessed with, SPM, and optical methods. Continuous miniaturization and increased complexity of manufactured components requires new profilometry methods that enable co-ordinate metrology as well as surface metrology. In this paper a new class of tactile sensing probe referred to as a standing wave sensor has been assessed for such applications. The probe is 7 μm in diameter and 3.5 mm in free length, and is incorporated into a scanning system capable of measuring surface texture and form in the same data set. This paper discusses the principle of operation of this sensor and presents example data obtained from measurements of surface texture standards, a precision thread, and form and surface texture of 128 μm hole.