Development of Evaluation Method for Delamination Strength Between Micro-Sized Materials in MEMS Devices
- PDF / 387,153 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 41 Downloads / 208 Views
0977-FF04-29
Development of Evaluation Method for Delamination Strength Between Micro-Sized Materials in MEMS Devices Chiemi Ishiyama, Junichi Hata, Satoru Koyama, Masato Sone, and Yakichi Higo Precision and Intelligence Labratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midoriku, Yokohama, 226-8503, Japan
ABSTRACT Our group developed a method for evaluating the delamination strength between micro-sized components and substrate using combining a micro-sized delamination test and FEM (Finite Element Method) analysis. We adopted a cylindrical shape for the micro-sized adhesive specimens on the substrate. A simple shape can be easily analyzed the stress field near the interface between the cylinder and substrate under shear loading with FEM. Micro-sized cylinders with four different diameters were fabricated on Si substrate by a photolithographic technique using epoxy type photoresist SU-8. According to our analysis of the test results by FEM, the delamination strength between the micro-sized SU-8 cylinder and Si substrate increased as the diameter of the cylinder increased. This suggests that the delamination loads determined by the delamination testing were influenced by natural cracks or defects in the material or at the interface. INTRODUCTION MEMS (Microelectromechanical Systems) are integrations of mechanical elements, sensors, and electronic components on common silicon or polymeric substrates. As products manufactured by microfabrication technology, MEMS are made up of micro-sized components with many bonding interfaces with substrate. The stress concentration at the bonding interfaces leads to delamination during the fabrication and servicing of MEMS. To ensure the durability and reliability of MEMS, the micro-sized materials comprising the systems must have high delamination strength. This presents a challenge, however, as the standard methods for evaluating the delamination strength of bulk-sized materials are hardly applicable on a micro-sized scale. Numerous delamination test method, which are approached from various directions, have been investigated to evaluate the delaminaton strength between thin films and substrate [1]. Before our latest study, however, there were no standardized methods for quantitatively evaluating the delamination strength of micro-sized materials. To address this problem, we developed such a method by combining a micro-sized delamination test with FEM analysis. We decided to adopt a cylindrical shape for the micro-sized adhesion specimens on the substrate, as simple shapes can be easily analyzed based on the stress fields under applied shear loading. Moreover, the loads can be properly applied to the specimens by actual testing. We used epoxy-type thick photoresist, SU-8, as the micro-sized cylindrical specimens, as the SU-8 resist can be fabricated into micro-sized structures with high aspect ratios by photolithography using UV waves.
ANALYSIS The model in Fig. 1 shows the delamination process between a cylindrical structure and substrate. The maximum stress is generat
Data Loading...
