The paper presents a mass production process for the manufacturing of smart label substrate components (interposers, antennas) based on laser ablation (by means of Excimer laser) in a reel-to-reel process (R2R) followed by a reel-to-reel electroplating process.
Digital imaging methods like Computer to Plate (CTP) solutions are progressive technologies to improve the quality and efficiency of prepress and printing workflows. In this environment the application of lasers for print form fabrication plays an increasingly important role because of the high machining rate, the high spatial resolution, the achievable high energy densities by fine focusing and the ability of digital modulation. This paper gives an overview of our laser based processes in flexography and gravure with a focus on the precise micro structuring of gravure print forms by direct laser ablation. Direct laser engraving into metallic cylinders is performed with a high power Q-switched Nd:YAG laser system at 70 kHz repetition rate tuned for high reproducibility and stability of the mean pulse energy (σ2 < 0.8%). An exact modulation technique allows fast variation and precise calibration of the energy of each single laser pulse as well as active modulation of the intensity profile of the beam. This method permits to engrave with each single laser pulse a complete cell and to define diameter and depth of each cell (the aspect ratio and the cell shape) independently and freely from pulse to pulse at a rate of 70 kHz, controlled by digital image data. Thus the cell shape can be optimized for the best ink transfer characteristic on different print substrates. Future developments in gravure industry and the requirements on fiber lasers and ultra short pulse lasers for an efficient industrial engraving process of print cylinders are discussed.
Two examples of our biophotonic research utilizing nanoparticles are presented, namely laser-based fluoroimmuno analysis and in-vivo optical oxygen monitoring. Results of the work include significantly enhanced sensitivity of a homogeneous fluorescence immunoassay and markedly improved spatial resolution of oxygen gradients in root nodules of a legume species.
In this paper we report on a new method for the generation of shaped holes by dynamical variation of the beam shape with a special optical system. It is based on using a q-switched Nd:YAG laser with 100 ns pulses at a wavelength of 1064 nm and an optical setup producing a photon tube. By variation of the beam divergence the shape of the photon tube can be variably modified. The optical system consists of a specially designed Galilean telescope and a focusing objective. The beam divergence can be changed in-situ by the Galilean telescope while processing. This enables to control diameter, length and angle of the photon tube. Shaped controlled structures are processed applying in-situ different optical fields which have been previously defined by simulations including aberrations and diffraction effects. As an example, the variable beam shaping resulted in through-going cylindrical bores as well as such ones with a defined conical inlet with respect to its taper angle and depth. Taper angles between 1 and nearly 50 degrees were realized by varying both the beam divergence and laser power. Furthermore, the variable beam shaping leads to improved and almost debris-free machining efficiency.
The increasing demands for miniaturization of electronic components and devices is observed. This caused a significant effect on the requirements faced on the printed circuit board (PCB) industry. PCB manufactures are driving for producing high density interconnect (HDI) boards at significantly reduced cost and reduced implementation time. The interconnection complexity of the PCB is still growing and today calls for 50/50 μm or 25/25 μm technology are real. Existing technologies, e.g. photolithograpy, are unable to offer such resolution. Laser Direct Imaging (LDI) technology is considered as an answer for these challenges. LDI is a process of imaging electric circuits directly on PCB without the use of a mask. The exposure of the photo-sensitive resist is carried out using a laser beam that is scanned across photoresist surface and switched on and off by means of a computer control system according to the electrical circuit pattern. Usually the laser used in the LDI generates a UV line, which is suitable to the commonly available photoresists. In this paper we present our recent results on the use a UV Nd:YAG laser (λ=355 nm) for direct imaging the circuitry pattern on the PCB covered by a photosensitive resist.
Laser cladding has many advantages compared to alternative non laser surface treatment processes like thermal spraying or deposition welding. It is possible to apply the laser energy into the base material in highly localized way. Therefore it is possible to build up claddings with a comparably high spatial accuracy. However, the efficiency of the process is generally low. For example the energy in terms of conducted heat into the base material beside the melt pool is lost. It can be shown that the so called heat conductivity losses can be reduced by optimizing the process parameters like scan velocity and beam intensity. Moreover, it was found that by coupling significantly more energy into the powder, both the energetic efficiency and the deposition efficiency were increased significantly. In this publication it is shown that it is possible with right parameter adaptation to reduce the processing time while simultaneously increasing the energetic process efficiency.
An experimental investigation on the laser cutting of thin metal sheets using a Q-switched diode pumped Nd:YAG laser and a conventional lamp pumped Nd:YAG laser with pulse duration of 150 ns and 0.3 ms respectively is described in this paper. Using the laser with short pulses the lower single pulse energy was not sufficient to remove the material along the entire thickness of the sheet in a single laser scan and multi-passes were required. However, short pulses with higher peak power densities allowed to produce precise cuts with a smaller width than long pulses. These two cutting processes by a multi-passes laser scan (using short pulses of 150 ns) and by a single laser scan (using long pulses of 0.3 ms) were compared in terms of laser energy, machining time and process performance. It was also observed that, when using short pulses, the groove geometry was different depending on the number of passes and the material removal rate due to the laser scan significantly decreases when the groove depth increases.
The laser scanner provides non-contact, high accuracy and high speed probing and has found many applications in manufacturing product inspection. Considerable effort has been put into extracting geometric features from point clouds. However, the research results for feature extraction from edge detection and computer vision do not meet the metrology requirement of high accuracy. Our test results have shown that features extracted from a point cloud obtained from laser scanning have poor accuracy compared to the result measured with a touch trigger probe, even with very careful qualification of the laser scanner. Generally, a circle extracted from a point cloud will be larger and the centre will be shifted compared with the result from a touch trigger probe. This paper investigates the causes of poor accuracy in laser scanning for geometric features and develops an algorithm to solve these problems. The test results show the algorithm developed works well and inspection accuracy and calculation speed have significantly improved.
UV picosecond laser pulses have been shown to be able to etch clean holes in polymers. This process has numerous applications in processing polymers. We present the results obtained by the investigation of the laser ablation process with picosecond pulses in 19 different organic materials. Micro-drilling and cutting of polymers were performed by the 355 and 266 nm radiation. The ablation rate versus laser fluence was investigated. Polymers showed the logarithmic ablation rate versus the laser fluence proving a well known Beer's model of laser ablation. Two ablation thresholds were observed in most of the polymers. One of them was below 1 J/cm2 with a low material removal rate. Another threshold was spread in the range of 3 - 30 J/cm2 and a rapid increase in the ablation rate was found above it. The processing of polymers was tested in fabrication of cavities relevant to different micro-devices. Combined cavities for the ink-jet printer head and micro-fluidic set were formed by laser etching. UV laser radiation with the picosecond pulse duration can be useful in manufacturing micro-systems for diverse technical applications.
In this paper, we have calculated the beam quality of practical unstable resonators under a variety of practical conditions. The effects of resonator geometrical parameters and misalignment were evaluated. Based on the Fresnel-Kirchhoff integral, the two-dimension phase and intensity have been calculated for practical positive branch unstable resonators. Using Second Order Moment (SOM) technique, Μ2 factor for such resonator was estimated. The results show that the beam quality is very sensitive to misalignment of the resonator. We also show that Μ2 factor increases with Fresnell number, while it decreases with magnification.
The quality factor of laser beams has attracted considerable attention and some different approaches have been reported to treat the problem. In this paper we analyze quality factor of laser beam and compare the effect of different aberrations on beam quality by expanding pure phase term of wavefront in terms of Zernike polynomials. Also we analyze experimentally the change of beam quality for different Astigmatism aberrations, and compare theoretical results with experimentally results. The experimental and theoretical results are in good agreement.
Fiber delivery of intense laser radiation is important for a broad range of application sectors, from medicine through to industrial laser processing of materials, and offers many practical system benefits relative to free space solutions. In recent years, photonic crystal fiber technology has revolutionized the dynamic field of optical fibers, bringing with them a wide range of novel optical properties that make them ideally suited to power delivery with unparalleled control over the beam properties. The DTI funded project: Photonic Fibers for Industrial beam DELivery (PFIDEL), aims to develop novel fiber geometries for use as a delivery system for high power industrial lasers and to assess their potential in a range of "real" industrial applications. In this paper we review, from an industrial laser user perspective, the advantages of each of the fibers studied under PFIDEL. We present results of application demonstrations and discuss how these fibers can positively impact the field of industrial laser systems and processes, in particular for direct write and micromachining applications.
Direct Write (DW) is an emerging group of technologies that allow printing of electronic and other functional components out of vacuum, directly onto structural parts and assemblies. With its ability to deposit a wide range of dissimilar materials, and transfer details directly from CAD/CAM, the process is very flexible, enabling rapid progress from design to fabrication. This paper provides an introduction to direct write, and describes the BAE Systems activities in this field. The paper also describes the use of lasers in direct write, and some provisional results on laser curing are presented.
The laser micromachining activities at the DTI have been going on since 2002. Here, we provide a review of the development of our laser laboratory including our recent investment in a femtosecond laser facility. In-depth information about the capabilities of this facility compared to the other lasers will be given. Finally, several industrially relevant case stories will be presented.