PTB News 2/2006 (148 kB) PTB News 2/2006, English edition, Issue August 2006The micro-assembly of miniaturized sensors and standards in metrological facilities is a new challenge to PTB’s Scientific Instrumentation Department. For this purpose, a high-precision multi-purpose robot – for which a patent has been applied for – has been developed which can position micro-objects with a reproducibility smaller than 1 μm with six degrees of freedom and large angular motion.
Commercially available micro-assembly devices are usually highly specialized. Their kinematics has only a small number of degrees of freedom or it can carry out only restricted angular motions of the tool towards the object within the workspace. The observation and control of the device with the aid of a camera often turns out to be difficult because the camera must be carried along or it is hardly possible to integrate it into the mechanical set-up.
Due to the special arrangement of its axes, the newly developed robot allows movements of the tool towards the object with 6 degrees of freedom in a cylindrical workspace of 60 mm in diameter and 25 mm in height to be performed. The possible angular motions are – depending on the axis of rotation – approx. ±90° or ±180° respectively. The increment for linear movements is 0.1 μm and smaller than 1’ for angular motions. High-precision positioning of micro-objects, which can additionally be oriented in large areas, is now possible. The small objects are manipulated by mechanical and suction grippers that have also been self-developed. It is thereby possible to follow the process thanks to a nearly unrestricted large-scale and high-resolution imaging from two vertical projections without any risk of collision (pixel size approx. 1 μm2). The whole facility is controlled by a PC-based system in a universal programming language. Significant movement and grip functions can be easily operated by means of a joystick. A universally usable robotics is thus available for the different micro-assembly tasks and with direct result control and inspection.
An interesting application of the new robot was, for instance, the assembly of stylus tips for scanning probe microscopy. Its use in high-vacuum for SEM observation of assembly processes is imminent.