Laser-induced thermochemical wet etching (or shortly ‘laser etching’) is a micromachining technique in which a focused laser beam irradiates a workpiece immersed in a liquid etchant to induce thermochemical reaction between the etchant and the workpiece (FIG. 1). Since the laser-generated excess heat is continuously removed by the relatively cold etchant, the workpiece can be processed with almost no thermal damage and the resulting microstructure has superior surface quality and shape clarity with no burr and debris.
Laser etching is a direct-writing process requiring no pattern mask, which allows an easy implementation of the technique as well as flexibility in the fabrication patterns. Laser etching system is relatively cost-effective than other process equipments such as electro-discharge machining (EDM) or Lithographie, Galvanoformung, Abformung (LIGA) systems. Due to these advantages of laser etching, micromachining using laser etching has been investigated for various applications since early 1980s.
In our laboratory, we developed a novel laser etching method in which the laser beam is delivered through an optical fiber in which the fiber tip is directly brought to the workpiece surface to irradiate and micromachine the workpiece (FIG. 2). Since the laser beam can be directly delivered through the optical fiber, the risk of exposing an operator to a high-powered laser light and time consuming alignment of optical components, serious problems in the conventional lens-based laser etching process, can be virtually eliminated. Also, by adopting optical fiber, the productivity of the etching process, which often places a severe limitation for practical application of a laser manufacturing technology, can be significantly enhanced through multiplexing of the laser beam using an optical splitter.
Due to the low thermal damage and high structural resolution achievable with laser etching process, laser etching has been applied for the fabrication of various metallic microdevices based on microgrooves and microholes, including micro heat pipe, microreactor, microfluidic channels, dye-sensitized solar cell, shadow mask of OLED, etc. (FIG. 3).