Short pulse laser microforming of thin metal sheets for MEMS manufacturing (original) (raw)
Related papers
Laser shock microforming of thin metal sheets
Applied Surface Science, 2009
Laser microforming Forming mechanisms Numerical modeling Experimental validation Continuous and long-pulse lasers have been used for the forming of metal sheets in macroscopic mechanical applications. However, for the manufacturing of micro-electromechanical systems (MEMS), the applicability of such type of lasers is limited by the long-relaxation-time of the thermal fields responsible for the forming phenomena. As a consequence of such slow relaxation, the final sheet deformation state is attained only after a certain time, what makes the generated internal residual stress fields more dependent on ambient conditions and might make difficult the subsequent assembly process from the point of view of residual stresses due to adjustment.
Laser Shock Microformingof Thin Metal Sheets with ns Lasers
2011
Continuous and long-pulse lasers have been used for the forming of metal sheets in macroscopic mechanical applications. However, for the manufacturing of micro-electromechanical systems (MEMS), the use of ns laser pulses provides a suitable parameter matching over an important range of sheet components that, preserving the short interaction time scale required for the predominantly mechanical (shock) induction of deformation residual stresses, allows for the successful processing of components in a medium range of miniaturization without appreciable thermal deformation.. In the present paper, the physics of laser shock microforming and the influence of the different experimental parameters on the net bending angle are presented.
Nanosecond Laser Shock Microforming of Thin Metal Components
Journal of Laser Micro/Nanoengineering, 2009
Laser shock microforming is conceived as a non-thermal laser forming method based on the high intensity laser induced shock waves capability to modify the tensional state of thin targets. The technique has the advantages of laser thermal forming (non-contact, tool-free and high precision), but, additionally, its minimally thermal character allows the preservation and improvement of mechanical material properties by inducing appropriate residual stress fields. In particular, the induction of compressive residual stress fields on the target surface is a desirable feature introducing additional protection of the formed parts against corrosion and fatigue crack propagation. The use of ns laser pulses provides a suitable parameter matching for the laser forming of an important range of sheet components used in MEMS that, preserving the short interaction time scale required for the predominantly mechanic (shock) induction of deformation residual stresses, allows for the successful processing of components in a medium range of miniaturization particularly important according to its frequent use in such systems. In the present paper, a discussion is presented on the physics of laser shock microforming and the influence of the different effects on the net bending angle. The experimental setup used for the experiments, the sample fabrication procedure and experimental results on the influence of repeated laser pulses on the net bending angle are also presented.
Experimental analysis of sheet metal micro-bending using a nanosecond-pulsed laser
The International Journal of Advanced Manufacturing Technology, 2013
Laser shock bending is a sheet metal micro-forming process using shock waves induced by a nanosecond-pulsed laser. It is developed to accurately bend, shape, precision align, or repair micro-components with bending angles less than 10°. Negative bending angle (away from laser beam) can be achieved with the high-energy pulsed laser, despite the conventional positive laser bending mechanism. In this research, various experimental and numerical studies on aluminum sheets are conducted to investigate the different deformation mechanism, positive or negative. The experiments are conducted with the sheet thickness varying from 0.25 to 1.75 mm and laser pulse energy of 0.2 to 0.5 J. A critical thickness threshold of 0.7-0.88 mm is found that the transition of positive-negative bending mechanism occurs. A statistic regression analysis is developed to determine the bending angle as a function of laser process parameters for positive bending cases.
Pulsed Laser Assisted Micromilling for Die/Mold Manufacturing
ASME 2007 International Manufacturing Science and Engineering Conference, 2007
Laser assisted machining is an alternative to conventional machining of hard and/or difficult-to-process materials which involves pre-heating of a focused area with a laser beam over the surface of the workpiece to cause localized thermal softening along the path of the cutting action. The main advantage that laser assisted machining has over conventional machining is the increased material removal rate and productivity. Laser assisted micromilling is a scaled down derivative of laser assisted machining assuming that the process effectiveness potentially exists at the meso/micro scale. It is well-known that continuous-wave (c.w.) lasers generate a wide and deep heat affected zone, and can cause microstructure alterations, potentially making laser assistance counter-productive at the meso/micro scale. The novel use of a pulsed laser in assisting micromilling enables processing of die/mold metal alloys that are typically hard and/or difficult-to-process in micro scale, while reducing the heat affected zone. A fairly innovative technique is introduced by thermally softening only the focused microscale area of the work material with induced heat from a pulsed laser, and material removal is performed immediately with micro mechanical end milling. The focus of this paper is to present a fundamental understanding of the pulsed laser assisted micromilling (PLAM), in particular, to investigate the influence of pulsing on microscale localized thermal softening by coupling with the finite element simulation of the micromilling process. Experiments and Finite element method-based process simulations for micromilling of AISI 4340 steel with and without the laser assistance are conducted to study the influence of the pulsed laser thermal softening on the reduction in cutting forces and its influence on the temperature rise in the cutting tool.
Development and Modeling of Laser Micromachining Techniques
Laser micromachining has great potential as a MEMS (micro-electromechanical systems) fabrication technique because of its materials flexibility and 3D capabilities. The machining of deep polymer structures with complex, well-defined surface profiles is particularly relevant to micro-fluidics and micro-optics. This paper presents the use of projection ablation methods to fabricate structures and devices aimed at these application areas. A better understanding of the mechanisms of thermodynamics and heat transfer in MEMS is desired to improve the thermal performance of MEMS due to the importance of these physical processes. Ablation rate of the laser depends on temperature, the material properties and accumulation of heat in the work material. In consequence, to control the laser processing, thermal distribution of the sample has to be determined, which can be made by modeling of laser ablation. By using such modeling tool, proper laser parameters can be determined easier and faster. Geometry of the domain under investigation varies during the simulation, because laser pulses remove material from the sample, thermal effects, photochemical and other phenomena still exist and so the modeling of laser ablation is a specialised problem. A two dimensional finite element model is developed in this work for laser ablation of polymers. Model has been further modified for fabrication of curved sufaces utilized in MEMS applications.
Micro structuring with highly repetitive ultra short laser pulses
For the first time an industrial high repetition ultra short laser source with pulse lengths less than 250fs, high beam quality M² better than 1.2, high pulse energies up to 8µJ, and repetition rates up to 25MHz (IMPULSE, Clark-MXR, Inc.) is applied for micro material processing. First results of stainless steel machining are presented to demonstrate the possibilities and limits of the machining process with high repetition laser pulses. Because of relatively high pulse energies at high pulse repetition rates completely new effects of laser material interaction are obtained. Principle mechanisms of heat accumulation and plasma or particle shielding processes are derived from experimental results, and models are discussed. Finally, formation of self organized laser induced micro structures is shown and the influence of machining parameters is presented.
Energy Level Effects on Deformation Mechanism in Microscale Laser
Laser microscale peen forming has recently received more and more attention as a viable laser processing technology as it not only imparts desirable residual stress for improvement of fatigue life of the material, but can also precisely control part deformation. In the present study, the effect of energy level on the deformation mechanism in laser microscale peen forming was investigated by both numerical and experimental methods. Deformation curvatures and residual stress distributions of both sides of the specimen, characterized by X-ray microdiffraction, were compared with the results obtained from FEM simulation. The forming mechanism for convex and concave bending was explained in terms of the resulting pressure, compressive stress distribution, and plastic strain. Differences in residual stress distribution patterns were also investigated as a function of the forming mechanism.
SN Applied Sciences, 2020
This paper presents the process development and characterization towards microstructural realization using laser micromachining for MEMS. Laser micromachining technique is environmental friendly, fast patterning and able to avoid multi steps in conventional lithography based microfabrication techniques. This research focuses on understanding the dimensional properties of materials of the laser beam on the silicon wafers where microstructures were fabricated. Four main parameters like rectangular variable aperture (RVA-XY) size, number of pulse, stage/table feed rate and laser energy play important role in laser ablation process. The pattern of the microchannel or line with 1 cm length was drawn by AutoCAD software or any CAD software. The pattern in the CAD software is then transferred onto the silicon wafer by using laser micromachining. Finally, high power microscope (HPM) and Stylus Profiler will be used as measurement tools for observing and analysing the width and depth of the microchannel structures fabricated by laser micromachining. When using bigger size of RVA, it will lead to bigger microchannel width. There are a little effects or almost comparable in term of microchannel depth if varying all parameters' value. Surface roughness test also needs to be considered before choosing the best setting for the laser ablation.