Automatic Microassembly System for Die Level Fabrication of MEMS Pressure Sensor

Die level fabrication of MEMS pressure sensors is limited by the manually manipulation process which require specially trained technicians. To reduce the production costs and simultaneously obtain high production quality, an automatic microassembly system for batch fabrication of MEMS sensors is developed. Firstly the automatic fabrication process is analyzed in detail, and an optimal system structure of dual-arm is presented. Secondly, the system is modularized into a set of autonomous modules which can adapt their structures and functions to various sizes of MEMS sensors, including positioning stages, three microscopy imaging systems, two flexible micromanipulators, a bonding center with three work cells, a fixture, two supply stations and auxiliary systems. Thirdly, major methodology issues in optomechatronic design of this system are introduced. An auto-focus method is introduced to get good image. The hybrid control of vision and force method is presented. An image based microvision control method is used to adjust the position of the dies and the glass base. And a coarse-to-fine positioning strategy under the microscope with the same magnification is employed to perform high-speed and high-precision visual positioning operations. A smart force sensor with one dimension is employed to sense and control the interactive force. To perform manipulations automatically, a control system, including a task planning level and a real-time execution level, is developed. Lastly, the productivity of the flexible microassembly system is validated by further experiments.