Mechanical Characterizations of Laser Microwelds for MEMS Packaging
- PDF / 550,138 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 82 Downloads / 192 Views
A5.82.1
Mechanical Characterizations of Laser Microwelds for MEMS Packaging Wei Han and Ryszard J. Pryputniewicz NEST – NanoEngineering, Science and Technology CHSLT – Center for Holographic Studies and Laser micro-mechaTronics Mechanical Engineering Department Worcester Polytechnic Institute Worcester, MA 01609 ABSTRACT Laser micromachining has proven to be a very powerful and successful tool for precision machining and microfabrication with applications in electronics, MEMS, medical, and biomedical fields. For MEMS fabrication and packaging, several approaches based on localized heating and bonding have been proposed such as localized eutectic bonding, fusion bonding, solder bonding, and chemical vapor deposition (CVD) bonding. However, these approaches are based on resistive heating which requires intimate contact at the electrodes, and this is not preferred for MEMS packaging applications. As a good alternative, laser microwelding has advantages of non contact, low heat distortion, high speed, high precision, and consistent weld integrity. Therefore, it is finding increasing use in MEMS fabrication and packaging applications. In laser microwelding, the material in the HAZ of the workpiece experiences heating, melting, and re-solidifying stages, and the final characterizations of the laser microwelds can be influenced by various factors such as the laser beam properties, the system cooling condition, and the surface roughness/reflectivity of the component. This paper presents characterization of laser microwelds, with emphasis on study of deformation and strength of the microwelds made by a Nd:YAG pulsed laser. Optical interferometry is used to nondestructively record fringe patterns of the shape and deformation of the laser microwelded workpiece before, during, and after the microwelding process, and tensile tests are performed to study strength of the laser microwelds as a function of different welding parameters. Results indicate that quality of the laser microwelds depends on selection of an appropriate set of parameters controlling the microwelding process.
INTRODUCTION Thin metal sheets are extensively used in industries making products for automotive, aerospace, and electronic components. Laser microwelding is considered to be a suitable joining process for thin sheet structures because it offers a number of attractive features such as high weld strength to weld size ratio, reliability, and a minimal heat-affected zone (HAZ). The laser microwelding process is very complex, including such phenomena as thermal conduction in a multiphase system, fluid flow, gas dynamics, and plasma effects. A number of investigations have been carried out for laser microwelding process, including the study of the reflection of laser beams by metal surfaces which affects the absorption of the laser energy [1], the study of weldability for various types of metals using pulsed laser beam [2], and the study of thermal stresses during laser welding [3,4]. However, to account for more than one phenomenon in analysis, sophisticate
Data Loading...
