Micromachining

Miniaturization is the order of the day. Until recently a decade ago traditionally watch parts were considered to be the micro components one can think off. Recent changes in society’s demand have forced us to manufacture variety of micro components used in different fields starting from entertainment electronics to be bio medical implants. Present day manufacturing processes used for miniaturization are the micro electronic fabrication techniques used for Micro Electro Mechanical Systems (MEMS). The limitation of all these processes is that they are applicable for producing 2D patterns and thickness of parts is very low; say a few microns and they are employed on materials such as Silicon and crystalline materials and not metals. Miniaturized parts may have overall sizes of a few millimeters but may have many features that fall in micron range. 

Also we need many such miniaturized parts may be with 3D profiles, that too made of metals in many fields like aerospace to bio-medical applications. A new candidate requiring micro products is the filed of biotechnology. In the medical field, diagnosis and surgery without pain are achieved through miniaturization of medical tools. Micromachining is one of the key technologies that can enable the realization of all of the above requirements for microproducts and fields with such requirements are rapidly expanding. If complementary machining processes are developed to overcome the above shortcomings, metallic miniature devices will be economically feasible reality.

The machining processes for micro/meso manufacturing can be derived from traditional machining processes such as turning milling, drilling, grinding, EDM, laser machining, etc., by judicious modification of these machines. Unit metal removal and improving equipment precision are the key factors for adapting the traditional machining processes to micro machining. When these two guidelines are set, the approach is almost correctly directed toward micromachining.

Laser Micromachining:

Unlike the CO2 or Nd: YAG lasers, Examier and Femto Second lasers, on the contrary, offer high-precision machining without the formation of a re-solidified layer and a heart –affected zone. There are two types of methods that are based on material removal by ablation. One uses a power source that emits a beam with very high quantum energy. If the energy exceeds the binding energy among atoms of the workpiece each molecule can be decomposed directly into atoms and removed from the workpiece. The other method uses an energy beam of which incident power density on the workpiece is extremely high such a high power enables the removal of the workpiece by vaporization, skipping the phase of melting in some cases, molecules are also decomposed in both types, microshapes can be generated by projecting mask patterns, whose size is reduced by using optics. Excimer laser and femto second lasers (hereafter referred to as FS lasers) are respectively typical examples of power sources for the above two types.

The Excimer laser is an ultraviolet laser which can be used to micromachine a number of materials without heating them, unlike many other lasers which remove materials without heating them, unlike many other lasers which remove materials without heating them, unlike many other lasers which remove material by burning or vaporising it. Higher accuracy can e achieved when a shorter wavelength, for example, 193nm of an ArF laser is applied. Since the applied photon energy is similar to the energy level of molecular bonds in plastics, the ideal targets for excimer laser machining are plastics, and similar materials and not metals. When a very high power is applied, the removal phenomenon involves a combination of heating and photon attack. FS lasers have short (femto second) pulse duration and high (tera watt) power and overcomes the above limitation.