Takahisa Masuzawa

State of the Art of Micromachining

Abstract Miniaturization is proceeding in various types of industrial products. Micromachining is the foundation of the technology to realize such miniaturized products. In this paper, the author summarizes the basic concepts and applications of major methods of micromachining. The basic characteristics of each group of methods are discussed based on different machining phenomena. Promising methods are introduced in detail hinting at suitable areas of application. Finally, the present state of these technologies is shown with examples of experimental and practical applications.

Micro-EDM for Three-Dimensional Cavities - Development of Uniform Wear Method -

Abstract In this paper, we present a new method, called uniform wear method, for 3D micro-EDM. Simple electrodes such as with round or rectangular section are used. Uniform wear at the end of the electrode was realized by layer-by-layer machining. This maintains the original electrode shape and converts the three dimensional electrode wear to a linear one. By compensating the linear electrode wear, complicated three dimensional cavities were successfully machined. This technique was developed for micromolds, but the applicability for normal size molds was also confirmed.

Laser Machining by short and ultrashort pulses, state of the art and new opportunities in the age of the photons

An overview is given of the applications of short and ultrashort lasers in material processing. Shorter pulses reduce heat-affected damage of the material and opens new ways for nanometer accuracy. Even forty years after the development of the laser there is a lot of effort in developing new and better performing concepts of lasers. The driving force is higher accuracy at reasonable cost, which is realised by compact systems delivering short laser pulses of high beam quality. Another trend is the shift towards shorter wavelengths, which are better absorbed by the material and which allows smaller feature sizes to be produced. Examples of new products, which became possible by this technique, are given. The trends in miniaturization QS predicted by Moore and Tanigychi are expected to continue over the next decade too thanks to short and ultrashort laser machining techniques.

Three-Dimensional Micromachining by Machine Tools

Abstract Machining technologies for three-dimensional microproducts are summarized by focusing on the methods using tools. After a discussion on the problems and the basic strategy concerning micromachining, promising methods for machining convex and concave shapes are introduced and discussed with respect to their state of the art. The methods introduced include WEDG, EDM, grinding, cutting, WECG, MEDM, microdrilling, micromilling, MUSM, micropunching, MLBM, electrolyte jet ECM, micro electroforming and micro injection molding.

Micro electro-discharge machining and its applications

A micro electro-discharge machining (MEDM) technology is presented. It allows machining of micro holes and shafts as small as 5 mu m in diameter with a best surface roughness of 0.1 mu m R/sub max/ and of roundness of 0.5 mu m, as well as a variety of complex shapes of equivalent accuracy. In the MEDM, machining for silicon with 10-100 Omega -cm resistivity is possible; machining up to a depth of 10 times the electrode diameter is easy, and the electrode wear is small. A prototype microair turbine of 2.2 mm external diameter, which is able to rotate at a speed of approximately 1000 r.p.m., is discussed.<<ETX>>

Drilling of Deep Microholes by EDM

Summary The paper deals with an experimental study on the machining of deep microholes by EDM. The system proposed is based on a horizontal EDM using water as the dielectric, the electrode being formed by the WEDG method. The result shows the applicability of this technique to the industrial production of microholes with the depth ten times the diameter which ranges down to 50μm.

Microultrasonic Machining by the Application of Workpiece Vibration

Abstract A new method for microultrasonic machining (MUSM) has been developed. In order to obtain high-precision tool rotation, the spindle mechanism employed in micro-EDM machines was introduced. Since the mechanism does not allow the vibration of tools, the workpiece was vibrated during machining. Using this setup, we have succeeded in machining microholes as small as 5pm in diameter in quartz glass and silicon. In this machining range, high tool wear posed a problem. To solve this problem, a sintered diamond (SD) tool was tested and was proven to be effective.

A Combined Electrical Machining Process for Micronozzle Fabrication

Abstract Smaller diameters are required for various types of precision nozzles. However, the accuracy of nozzle holes is a problem in mechanical machining processes and the choice of inner shapes is limited. A combined process with EDM, ECM and electroforming is proposed for the production of nozzles with small diameters and various inner shapes. Nozzle holes with the diameters of 6-100 micrometers were successfully produced with good concentricity to the outer profile. Some technical characteristics of the process were also investigated.

The MEMSNAS process: microloading effect for micromachining 3-D structures of nearly all shapes

We propose a technological process for microfabrication of three-dimensional (3-D) structures with nearly all shapes. This is a one-mask process that uses equipment, widespread in the microelectronics laboratories and industry. The main idea is to take advantage from the microloading effect of reactive ion etching (RIE) in order to obtain multiple levels of heights in an array of microholes of different diameters. A 3-D profile results from an overlap of the neighboring microholes due to the isotropic nature of the etching. The final continuous and smooth 3-D structure is obtained after removal of the mask material and a second isotropic RIE step. This fabrication process was validated with the realization of various 3-D structures including microlenses, etched in a 30 /spl mu/m deep cavity, with 375 /spl mu/m in radius and 10 /spl mu/m in height (sag). The resulting structures have shown a roughness down to 25 nm. A quantitative experimental study led to the calibration of three different processes and to an empirical theoretical model, which can serve as a basis of design rules for further fabrication of 3-D microstructures.

Vibroscanning Method for Nondestructive Measurement of Small Holes

Summary A new method for measuring inner dimensions of small holes was developed. The electrical contact between a vibrating feeler and the inner surface of a hole is detected, and the duty cycle of the contact is measured. Through a controlled scan by a feeler with a constant duty cycle, data on the ups and downs of the surface profile are obtained. Through the application of this principle, a φ 200μm hole with the depth of 700μm was successfully measured, and geometrical data such as straightness, declination and taper were obtained.