• Journal of the Korean Society for Precision Engineering
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• v.30 no.12
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• pp.1265-1271
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• 2013

In this work, modeling and analysis of thermal effects laser drilling under water for ceramics were presented. Laser is a unique tool for machining ceramics due to the characteristic of non-contact material removal. However, ablation by a laser often induces a thermal effect on the material and an increased heat-affected-zone or deposition of debris can be observed on the machined parts. The underwater surrounding improved a heat transfer rate to cooling down the machined part and could prevent any deposition of debris near the machined surfaces and edges. The heat modeling was applied to obtain the temperature distributions as well as temperature gradients between the material and surroundings. The cooling effect of the underwater laser drilling was improved and a more stable temperature distribution was calculated. The actual laser drilling results of ceramic laser drilling were presented to verify the effects of underwater laser drilling.

• Korean Journal of Animal Reproduction
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• v.22 no.3
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• pp.287-292
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• 1998

The objective of this study was to test whether ZP drilling using a 1.48$\mu$m diode laser beam on mouse IVF embryos becomes effective the hatching and normal in vivo development, as a preliminary test for obtaining the additional proof that the 1.48$\mu$m diode laser could be used safely for human applications. The results obtained in this experiment were as follows: when the hatched rates of mouse embryos by laser ZP drilling according to the embryonic stage were examined until 72 hr (in case of blast tocyst: day 4 after IVF) or 120 hr (in case of 4-cell: day 2 after IVF) after treatment, the d data of laser drilled blastocysts (81.8%) was significantly higher than those of control (hatching blastocyst: day 4 after IVF) (54.2%) and laser drilled 4-cell embryos (45.5%) (p<0.05). When the effect of laser drilling on implantation rates following embryo transfer in day 3 synchronized pseudopregnant recipients was examined, the l laser drilled group (48.7%) was slightly higher than that of control group (43.6%). In addition, when the several pregnant mice delivered in two groups were analysed their chromosomal normality and tested reproductive ability, all p pups were presented normal chromosomal number (n=40) and showed normal growth and reproductive ability. Therefore, these results dem-onstrated that ZP drilling using a 1.48$\mu$m diode l laser can increase the embryo hatching and ind duce the normal pregnancy of mouse embryos.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.99-103
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• 2012

Presently, A glass is widely used in telecommunication system, optoelectronic devices and micro electro mechanical systems. Micro drilling of glass using the laser can save processing cost and improve the accuracy. This paper experiments micro drilling using KrF excimer laser on the pyrex glass of $500{\mu}m$ thickness. We have experiment to find out optimum laser machining conditions of micro drilling of glass and ablation depth and influence by processing parameter suc'h pulse repetition rate, energy density and number of pulses. Pulse repetition rate don't influence ablation depth at the micro drilling of pyrex glass. Energy density influence micro drilling of parallelism and maximum thickness that can be drilled. Ablation depth is most influenced by number of pulses.

• Korean Journal of Animal Reproduction
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• v.22 no.2
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• pp.163-169
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• 1998

본 실험은 체외 생산된 소 배반포기배에 대한 laser drilling 처리가 배의 부화율에 미치는 영향을 조사하고자 실시하였다. 그 결과는 다음과 같다. 소 수정란의 체외 발달율을 조사하였던 바, 82.3%의 난할율( 2-세포기)과 체외수정 후 배양 7일째에 32.6%의 배반포 발달율을 나타내었다. 이렇게 생산된 배반포기배에 laser drilling 효과를 조사하였던 바, 처리 후 24시간째의 부화진행율(90.0%)은 대조군(44.4%)보다 유의하게 높게 나타났다(p<0.0001). 또한, 처리 후 48시간째의 부화율(68.0%)도 대조군(33.3%)보다 유의하게 높게 나타났다. 이러한 결과는 laser drilling이 체외 생산된 소 배반포기배의 부화진행율과 부화율을 유의하게 증가시킬 수 있다는 것을 알 수 있었다(p<0.001).

• 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.

• 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.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.10
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• pp.14-22
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• 2010

The most costly and time-consuming process in the fabrication of today's multi-layer circuit board is drilling interconnection holes between adjacent layers and via holes within a layer. Decreasing size of via holes being demanded and growing number of via holes per panel increase drilling costs. Component density and electronic functionality of today's multi-layer circuit boards can be improved with the introduction of cost-effective, variable depth laser drilled blind micro via holes, and interconnection holes. Laser technology is being quickly adopted into the circuit board industry but can be accelerated with the introduction of a true production laser drilling system. In order to get optimized condition for drilling to FPCB (Flexible Printed Circuit Board), we use various drill pattern as drill step. For productivity, we investigate drill path optimization method. And for the precise drilling the thermal drift of scanner and temperature change of scan system are tested.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.10
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• pp.40-44
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• 2010

Laser drilling is an enabling technology for Through Silicon Via (TSV) interconnect applications. Recent advances in picoseconds laser drilling of blind, micron sized vias in silicon is presented here highlighting some of the attractive features of this approach such as excellent sidewall quality. In this study, we dealt with comparison of heat affection around drilled hole between a picosecond laser and a nanosecond laser process under the UV wavelength. Points which special attention should be paid are that picosecond laser process lowered experimentally recast layer, surface debris and micro-crack around hole in comparison with nanosecond laser process. These finding suggests that laser TSV process has possibility to drill under $10{\mu}m$ via. Finally, the laser drilling platform was constructed successfully.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.745-746
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• 2008

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.231-232
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• 2010