• Journal of the Korean Solar Energy Society
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• v.31 no.4
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• pp.103-111
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• 2011

Laser drilling of vias is the one of key technologies in developing Emitter-Wrap Through(EWT) solar cell which is particularly attractive due to the use of industrial processing and common solar grade p-type silicon materials. While alternative economically feasible drilling process is not available to date, the processing time and laser induced damage should be as small as possible in this process. This paper provides an overview on various factors that should be considered in using the laser via drilling technology for developing highly efficient and industrially applicable EWT solar cells.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.2
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• pp.53-57
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• 2014

Thin glass (< 100 microns) is a promising material from which advanced interposers for high density electrical interconnects for 2.5D chip packaging can be produced. But thin glass is extremely brittle, so mechanical micromachining to create through glass vias (TGVs) is particularly challenging. In this article we show how laser processing using deep UV excimer lasers at a wavelength of 193 nm provides a viable solution capable of drilling dense patterns of TGVs with high hole counts. Based on mask illumination, this method supports parallel drilling of up over 1,000 through vias in 30 to $100{\mu}m$ thin glass sheets. (We also briefly discuss that ultrafast lasers are an excellent alternative for laser drilling of TGVs at lower pattern densities.) We present data showing that this process can deliver the requisite hole quality and can readily achieve future-proof TGV diameters as small $10{\mu}m$ together with a corresponding reduction in pitch size.

• Laser Solutions
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• v.17 no.2
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• pp.5-10
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• 2014

Aluminum has been widely used in the electric applications because of light metals. When mechanical element is periodically moving with contacting other surfaces, the anodizing process for aluminum is useful for avoiding the abrasive damage. The anodized element has quietly different characteristics with respect to the distribution of hardness and crystal structure. In this work, the laser drilling of anodized surface is studied experimentally. Fusion drilling method - laser drilling with inert gas blowing - is used. The effect of various process parameters (gas pressure, laser power, focus position) is investigated with respect to the hole size and circularity.

• Laser Solutions
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• v.13 no.4
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• pp.7-13
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• 2010

Today, the most common process for generating Through Silicon Vias (TSVs) for 3D ICs is Deep Reactive Ion Etching (DRIE), which allows for high aspect ratio blind holes with low surface roughness. However, the DRIE process requires a vacuum environment and the use of expensive masks. The advantage of using lasers for TSV drilling is the higher flexibility they allow during manufacturing, because neither vacuum nor lithography or masks arc required and because lasers can be applied even to metal and to dielectric layers other than silicon. However, conventional nanosecond lasers have the disadvantage of causing heat affection around the target area. By contrast, the use of a picosecond laser enables the precise generation of TSVs with less heat affected zone. In this study, we conducted a comparison of thermalization effects around laser-drilled holes when using a picosecond laser set for a high pulse energy range and a low pulse energy range. Notably, the low pulse energy picosecond laser process reduced the experimentally recast layer, surface debris and melts around the hole better than the high pulse energy process.

• Current Optics and Photonics
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• v.3 no.5
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• pp.451-457
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• 2019

Laser processing using holograms can greatly improve processing speed, by spatially distributing the laser energy on the target material. However, it is difficult to reconstruct an image with arrays of closely spaced spots for laser processing, because the specklelike interference pattern prevents the spots from getting close to each other. To resolve this problem, a line target was divided in two, reconstructed with orthogonally polarized beams, and then superposed. Their optical reconstruction was performed by computer-generated holograms and a pulsed laser. With this method, we performed two-dimensional (2D) laser drilling of polyimide film, with a kerf width of $20{\mu}m$ and a total processing length of 20 mm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.21-22
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• 2007

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.867-875
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• 2004

In order to inspect burr geometry and hole quality in micro-drilling processes, a cost-effective method using an image processing and shape from focus (SFF) methods on the machine tool is proposed. A CCD camera with a zoom lens and a novel illumination unit is used in this paper. Since the on-machine vision unit is incorporated with the CNC function of the machine tool, direct measurement and condition monitoring of micro-drilling processes are conducted between drilling processes on the machine tool. Stainless steel and hardened tool steel are used as specimens, as well as twist drills made of carbide are used in experiments. Validity of the developed system is confirmed through experiments.

• Laser Solutions
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• v.6 no.1
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• pp.9-16
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• 2003

Micromachining using the DPSS 3rd Harmonic Laser (355nm) has outstanding advantages as a UV source in comparison with Excimer lasers in various aspects such as maintenance cost, maskless machining, high repetition rate and so on. It also has the greater absorptivity of many materials in contrast to other IR sources. In this paper, the process for micro-drilling of blind hole in Cu/PI/Cu substrate with the DPSS UV laser and the scanning device is investigated by the experimental methods. It is known that there is a large gap between the ablation threshold of copper and that of PI. We use the Archimedes spiral path for the blind hole with different energy densities to ablate the different material. Finally, the blind via hole of diameter 100$\mu\textrm{m}$ and 50$\mu\textrm{m}$ was drilled.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.1 no.1
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• pp.109-116
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• 2002

Resently, reduction of industrial products in size and weight has increased by the application of micro-drill for gadgets of high precision and gave rise to a great interest in a micro-drilling. Due to the lack of tool stiffness and the chip packing, micro-drilling requires not only the robust tool structure which has not affected by the vibration, but also the effective drilling methods designed to prevent tool fracture from cutting troubles. Firstly, this paper presents a new manufacturing process of micro-drill for improving the product rate and an optimum shape of micro-drill for lengthening the tool life, and secondly suggests between tool life and drilling torque acquired in the inprocess monitoring system.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2002.05a
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• pp.61-64
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• 2002