Controlled process for polymer micromachining using designed pulse trains of a UV solid state laser (original) (raw)
Related papers
2004
Laser drilling becomes of increasing importance when hole diameter is in the range of 10 to 50 mum, for which conventional alternative approaches are becoming difficult and cost inefficient. Furthermore, it is viewed as the technique of choice for a number of composite materials and hard materials which are not readily processed at the microscopic level by contact mechanical tools. We have demonstrated that suitable experimental conditions are capable of producing microholes with record aspect-ratio (up to 600) in pure polymers like PET, PI, PC, PS, PMMA, PEEK,... For example holes of diameter typically 30 mum can be as long as 18 mm, depth at which the drilling rate is getting nearly zero and the profile stationary. Other materials (metals, ceramics) which can be similarly laser microdrilled do not exhibit such very high aspect-ratio. The mechanisms of the drilling process have been studied in details and an original analytical model has been constructed recently. The various experimental results, obtained with the KrF laser, will be reviewed with emphasis on the parameters leading to formation of good holes with high aspect-ratio. For the application it is also important to note that such high values of aspect-ratio are obtained with regular configuration of the KrF laser giving a standard divergence of 3 mrad. However as shown by the model there is still room for improvement by using a beam with a lower divergence (theoretical limit is 0.2 mrad). Further experimental work is now in progress.
Laser Micromachining of a Biodegradable Polymer
2001
This paper reports on UV laser micromachining of a biodegradable polymer for applications in biomedical engineering. Parametric studies have been conducted on Poly-vinyl Alcohol (PVA), a biodegradable polymer, to produce micro channels and micro holes. Laser micromachining of micro channels is studied using a XeCl excimer laser at 308 nm wavelength and laser micro drilling is studied using a Q-switched Nd: YAG laser at 266 nm wavelength. Feature sizes ranging from 4 to 10 μm were obtained for the micro holes and the features of micro channels ranged from 33 to 65 μm wide and 22 to 123 μm deep. This work demonstrated that UV laser micromachining is a well-suited technique for biodegradable polymers with minimum thermal damage to the surrounding material.
Micro-hole processing of polyimide film by ultra-short laser pulses and its applications
Micro machining of a polyimide film with ultrashort pulsed laser was demonstrated. A through-hole with a diameter of less than 10 µm could be produced by optimizing the pulse duration, repetition rate, and number of shots. Thermal damage around the through-hole can be made negligibly small when the pulse duration was shorter than 140 fs. We also found that the minimum shot number needed for the creation of a through-hole becomes smaller as the repetition rate of laser shot increases. On the basis of the optimum irradiation condition, we demonstrated laser cutting filling in through-holes with diameters of 9 µm by a plating process.
High-aspect-ratio microdrilling of polymers with UV laser ablation: experiment with analytical model
Applied Physics A-materials Science & Processing, 2003
Systematic experimental studies of KrF laser microdrilling in polymers (PMMA, PET, PS, PC, PI, PEEK) have led to high-aspect-ratio microholes (up to 600) in a final stationary profile. From these results, an original theory is derived, which gives an analytical modeling of the multi-pulse ablation process. In the experiments holes with diameters in the range of 10 to 100 μm and from one to several tens of millimeters in depth, depending on fluence, are obtained for various polymers. The stationary depth increases with fluence and this dependence is well reproduced by the present model. The particular mechanism of radiation propagation and absorption inside the deep laser keyhole is clarified, and does not suggest a significant channeling of the radiation in the forming hole. This mechanism alongside the angular divergence of the beam are important key factors for the mathematical description of high-aspect-ratio laser drilling. As a result (a) the controlling factors of drilling are outlined; (b) final keyhole profile and depth vs. incident fluence are calculated for the rectangular, Gaussian and other spatial distributions of the beam and the comparison with the experiment is given; and (c) the laser drilling is optimized, i.e. the matching conditions for the level and distribution of laser intensity, parameters of the optical focusing scheme and material parameters are derived in an explicit analytical form, allowing us to produce deep keyholes with practically parallel side walls and aspect ratios as high as 300–600.
High aspect-ratio micromachining of polymers with an ultrafast laser
Applied Surface Science, 2002
Laser ablation of various polymers has been studied using a beam of 100 fs laser pulses at a wavelength of 800 nm. For a beam focussed by a plano-convex lens, high-quality machining of holes with diameters 20±40 mm and depths 300±400 mm (aspect ratio greater than 10) has been achieved. When projection patterning is carried out with a rectangular pinhole, arrays of micro-strings have been observed deep in the bulk of the sample. The micro-strings have diameters as small as 2 mm (about three times the wavelength) and lengths greater than 10 mm (aspect ratio 5000). The achievement of the high aspect ratios and the formation of the arrays of micro-strings are discussed. #
Micromachining Of Poly (Methyl Methacrylate)Polymerusing Krfexcimer Laser
2018
In the present work micromachining of PMMA was carried out using KrF excimer laser. Excimer laser pulse with a wavelength of 248 nm was generated with a coherent COMPexPro 110 excimer laser system. A micro-hole of Ø150 μm was machined on PMMA substrate during the experimentation. The PMMA substrate was mounted on the translation stage. The PMMA substrates were ex-posed to different number of pulses (1, 2, 5, 10, 20, 50 and 100) at repetition rate of 2, 5 and 10 Hz respectively by keeping the pulse energy unchanged at 200 mJ. In the present experimentation, the effect of pulse repetition rate and number of pulses on ablation depth has been investigated. The experimental results for micromachining demonstrate ablation process as a photo-chemical mechanism. The results of the experimentation have revealed that, ablation depth is directly proportional to pulse number & pulse repetition rate has no significant effects on the ablation depth.
Hole qualities in laser trepanning of polymeric materials
Optics and Lasers in Engineering, 2012
The present study focuses the effect of four input controllable laser cutting variables on the hole taper and hole circularity in laser trepan drilling of polymeric materials. Experiments have been conducted on acrylonitrile butadiene styrene (ABS) and polymethyl methacrylate (PMMA) polymer sheets. Laser power, assist gas pressure, cutting speed and stand-off distance were selected as independent process variables. Three different holes of diameters 2 mm, 4 mm and 6 mm were drilled in these work materials of 5 mm thickness. A Taguchi L9 orthogonal array with four factors and three levels of each factor was used to plan and conduct the experiments in order to obtain required information with reduced number of experiments. The process performance was ascertained in terms of hole taper and hole circularity. Initial analysis involved in determining the effect of the four process variables on hole taper and circularity for these two polymers at three different hole diameters. From ANOVA analysis, the optimum levels of the four process variables with respect to materials and hole diameters were evaluated. As it was found that the optimum levels of four process variables were different for different hole size and materials, additional analysis was conducted to incorporate the effect of material and hole diameter on the hole taper. From the analysis, the optimum combinations were obtained at compressed air pressure of 2.0 bar, laser power of 500 W, cutting speed of 0.6 m/min, stand-off distance of 5.0 mm, hole diameter of 2.0 mm and material of PMMA. These combinations produced the minimum taper in the hole. The circularity of the hole was more at the entrance than the exit when ABS polymer was laser drilled while in PMMA, the hole was more circular at the exit than the entrance.
UV Laser Micromachining of Polymers for Microfluidic Applications
Journal of the Association for Laboratory Automation, 2002
W e have recently begun to explore the use of UV laser ablation micromachining to construct microfluidic devices in polymers. This technique can create microchannels rapidly and modify the resulting polymer surface in a single step. By ablating under different atmospheres, it is possible to alter both the surface chemistries and physical surface morphologies of the microchannels. We have employed electroosmotic flow measurements, chemical mapping, and optical microscopy to characterize the microfluidic devices. In addition, we have studied the parameters affecting the ablation, such as the laser wavelength, laser fluence, laser firing repetition rate, and the material being ablated.
Effects of excimer laser illumination on microdrilling into an oblique polymer surface
Optics and Lasers in Engineering, 2006
In this work, we present the experimental results of micromachining into polymethymethacrylate exposed to oblique KrF excimer laser beams. The results of low-aspect-ratio ablations show that the ablation rate decreases monotonously with the increase of incident angle for various fluences. The ablation rate of high-aspect-ratio drilling with opening center on the focal plane is almost independent of incident angles and is less than that of low-aspectratio ablation. The results of high-aspect-ratio ablations show that the openings of the holes at a distance from the focal plane are enlarged and their edges are blurred. Besides, the depth of a hole in the samples oblique to the laser beam at a distance from the focal plane decreases with the increase of the distance from the focal plane. The number of deep holes generated by oblique laser beams through a matrix of apertures decreases with the increase of incident angle. Those phenomena reveal the influence of the local light intensity on microdrilling into an oblique surface.