마이크로 금형 부품을 위한 마이크로 절삭가공 기술

하석재,박정연,김건희,윤길상 한국금형공학회 2019 한국금형공학회지 Vol.13 No.1

In this paper, we studied the micro tool deflection, micro cutting with low temperature, and deformation of micro ribs caused by cutting forces. First, we performed an integrated machining error compensation method based on captured images of tool deflection shapes in micro cutting process. In micro cutting process, micro tool deflection generates very serious problems in contrast to macro tool deflection. To get the real images of micro tool deflection, it is possible to estimate tool deflection in cutting conditions modeled and to compensate for machining errors using an iterative algorithm correcting tool path. Second, in macro cutting fields, the cryogenic cutting process has been applied to cut the refractory metal but, the serious problem may be generated in micro cutting fields by the cryogenic environment. However, if the proper low temperature is applied to micro cutting area, the cooling effect of cutting heat is expected. Such effect can make the reduction of tool wear and burr formation. For verifying this passibility, the micro cutting experiment at low temperature was performed and SEM images were analyzed. Third, the micro pattern was deformed by the cutting forces and the shape error occurred in the sidewall multi-step cutting process were minimized. As the results, the relationship between the cutting conditions and the deformation of micro-structure during micro cutting process was investigated.

Economic evaluation and machining performance in Ti-6Al-4V titanium alloy milling by integrated CO 2 & MQL injection system

하석재,임동욱,김지훈,박정연,송기혁 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.9

In this study, a twin-fluid atomizing nozzle was fabricated to inject an integrated mixture of minimum quantity lubrication (MQL) mist and cryogenic gases, such as CO 2 and LN 2 , to the machining area of the tool in the milling of (Ti-6Al-4V) titanium alloy. The machining performance of the nozzle was analyzed by evaluating the cutting temperature, cutting force, and tool wear. The integrated injection of CO 2 and MQL mist was then compared with other cutting fluid application techniques, such as dry machining, cryogenic gas injection, and MQL mist for an economic evaluation. The experimental results revealed that this integrated injection reduced the cutting temperature by approximately 23 % (at 100 °C) for the same flow rate, while rarely occurred tool wear for the same cutting volume. Although it incurs an additional cost for the CO 2 cryogenic gas and MQL mist, it effectively reduces the cutting tool wear as compared to other cutting fluids, under the same cutting conditions and flow rate. It also increases productivity and reduces cost by improving the machining performance.

Influence of cutting temperature on carbon fiber-reinforced plastic composites in high-speed machining

하석재,김기범,양지경,조명우 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.4

Carbon fiber-reinforced plastic (CFRP) composites have been widely used in many industries, including aerospace, automobiles, medical devices, and building materials, because of their good material properties, such as weight, rigidity, strength, and wear resistance. We experimentally evaluated the high-speed machining characteristics of CFRP composites. First, dry-cutting experiments were performed to test prepared CFRP specimens. Above a certain cutting speed, the epoxy matrix melted owing to the heat caused by the friction between the tool and specimen. Next, high-speed cutting experiments were performed at a low temperature (approximately -20 °C). Many sensors were used to investigate the characteristics of the high-speed cutting process, and the results were analyzed.

고속 라우터 기술현황과 전망

하석재,최양희 한국통신학회 1999 정보와 통신 Vol.16 No.12

DSI 성형을 이용한 금속/플라스틱 복합 부품 제조에 관한 연구

하석재,차백순,고영배,Ha, Seok-Jae,Cha, Baeg-Soon,Ko, Young-Bae 한국금형공학회 2020 한국금형공학회지 Vol.14 No.4

Various manufacturing technologies, including over-molding and insert-injection molding, are used to produce hybrid plastics and metals. However, there are disadvantages to these technologies, as they require several steps in manufacturing and are limited to what can be reasonably achieved within the complexities of part geometry. This study aims to determine a practical approach for producing metal/plastic hybrid components by combining plastic injection molding and metal die casting to create a new hybrid metal/plastic molding process. The integrated metal/plastic hybrid injection molding process developed in this study uses the proven method of multi-component technology as a basis to combine plastic injection molding with metal die casting into one integrated process. In this study, the electrical conductivity and ampacity were verified to qualify the new process for the production of parts used in electronic devices. The electrical conductivity was measured, contacting both sides of the test sample with constant pressure, and the resistivity was measured using a micro ohmmeter. Also, the specific conductivity was subsequently calculated from the resistivity and contact surface of the conductor path. The ampacity defines the maximum amount of current a conductive path can carry before sustaining immediate or progressive deterioration. The manufactured hybrid multi-components were loaded with increasing currents, while the temperature was recorded with an infrared camera. To compare the measured infrared images, an electro-thermal simulation was conducted using commercial CAE software to predict the maximum temperature of the power loaded parts. Overall, during the injection molding process, it was demonstrated that multifunctional parts can be produced for electric and electronic applications.

Auto-Focusing 미세부품 Yoke 조립 자동화 모듈 개발

하석재,박정연,박규섭,윤길상 한국금형공학회 2019 한국금형공학회지 Vol.13 No.1

Smart-phone in the recently released high-end applied to the camera module is equipped with the most features auto focusing camera module. Also, auto focusing camera module is divided into voice coil motor, encoder, and piezo according to type of motion mechanism. Auto focusing camera module is composed of voice coil motor (VCM) as an actuator and leaf spring as a guide and suspension. VCM actuator is made of magnet, yoke as a metal, and coil as a copper wire. Recently, the assembly as yoke and magnet is made by human resources. These process has a long process time and it is difficult to secure quality. Also, These process is not economical in cost, and productivity is reduced. Therefore, an automatic assembly as yoke and magnet is needed in the present process. In this paper, we have developed an automatic assembly device that can automatically assemble yoke and magnet, and performed verifying performance. Therefore, by using the developed automatic assembly device, it is possible to increase the productivity and reduce the production cost.

티타늄 합금 플랜지 볼트 성형에서의 단조력 간접 측정을 위한 열간 단조 공정 모니터링에 관한 연구

하석재,최두선,이동원,송기혁,Ha, Seok-Jae,Choi, Doo-Sun,Lee, Dong-Won,Song, Ki-Hyeok 한국금형공학회 2021 한국금형공학회지 Vol.15 No.1

The objective of this study is to introduce the new possibility of sensing technology based on inductive displacement sensors to monitor the status of wheel position in the hot forging process. In order to validate effectiveness of proposed sensing technology, the indirect forging force measurement with displacement sensor was applied into a typical closed hot forging die-set used for the manufacturing of flange bolts. The locations to implement the displacement sensor were selected carefully by simulating forming process and static structural. From the measurement results of the forging force change during one hot forging cycle, it was found that the proposed monitoring system can provide useful information to understand the detailed behaviors of die-set in the closed hot forging process.

머신비전에 의한 LED Chip Package 형광물질 토출형상 측정

하석재(Ha, Seok-Jae),김종수(Kim, Jong-Soo),조명우(Cho, Meyong-Woo),최종명(Choi, Jong-Myung) 한국산학기술학회 2013 한국산학기술학회논문지 Vol.14 No.5

본 연구는, LED 칩 패키지에 있는 토출된 형광체 수지의 모양을 인라인 측정을 통해 개발된 검사 시스템을 기초로 한 효율적인 머신 비전에 관한 연구이다. 형광체의 반투명 특성 때문에 조사된 빛이 칩의 표면뿐만 아니라 하 단 부에서도 반사된다. 이러한 현상이 LED 칩 검사의 신뢰성을 저하시키기 때문에 적절한 조명 광학계를 결정하기 위해 백색광 LED 와 635nm의 레이저 슬릿 빛을 이용하여 검사하였다. 또한, 광 삼각측정법을 이용해 정반사와 분산 반사법으로 검사를 수행하였다. 실험 결과 백색 슬릿 광과 정반사 반사법의 조합이 가장 좋은 검사 결과를 낸다는 것 을 확인할 수 있었다. Catmull-Rom 스플라인 보간법을 이용하여 측정된 데이터를 부드러운 표면 형상으로 나타내었 다. 측정 결과를 통해 개발된 시스템이 LED 칩 패키징 공정에 인라인 검사에 성공적으로 적용될 수 있다는 결론을 내릴 수 있다. In this study, an efficient machine vision based inspection system is developed for the in-line measurement of phosphor resin dispensing shapes on LED chip package. Since the phosphor resin (target material) has semitransparent characteristics, illuminated light beam is reflected from the bottom of the chip as well as from the surface. Since such phenomenon can deteriorate inspection reliability, a white LED and a 635nm laser slit beams are experimentally tested to decide suitable illumination optics. Also, specular and diffuse reflection methods are tested to decide suitable optical triangulation. As a result, it can be known that the combination of a white slit beam source and specular reflection method show the best inspection results. The Catmull-Rom spline interpolation is applied to the obtained data to form smoother surface. From the results, it can be conclude that the developed system can be sucessfully applied to the in-line inspection of LED chip packaging process.

반응표면분석법을 이용한 LED Die Bonding 공정능력 최적화

하석재(Ha, Seok-Jae),조용규(Cho, Yong-Kyu),조명우(Cho, Meyong-Woo),이광철(Lee, Kwang-Cheol),최원호(Choi, Won-Ho) 한국산학기술학회 2012 한국산학기술학회논문지 Vol.13 No.10

LED 칩 패키징에서 다이 본딩은 웨이퍼에서 분할된 다이를 리드 프레임에 접착제로 고정시켜 칩이 다음 공 정을 견딜 수 있는 충분한 강도를 제공하는 중요한 공정이다. 본 논문에서는 PLCC 구조 LED 패키지 프레임에 소형 제너 다이오드를 부착하는 다이 본딩 공정능력의 최적화를 위하여 공정에 영향을 미치는 여러 인자를 분석하여 반응 표면분석법을 적용하여 그 결과를 도출하였다. 인자를 분석하여 5인자 3수준 4반응치를 고려하여 실험계획법을 수립 하였으며, 그 결과 모든 반응치의 목표를 만족하는 최적 조건을 확보할 수 있었다. In LED chip packaging, die bonding is a very important process which fixes the LED chip on the lead frame to provide enough strength for the next process. This paper focuses on the process optimization of a LED die bonding, which attaches small zener diode chip on PLCC LED package frame, using response surface analysis. Design of experiment (DOE) of 5 factors, 3 levels and 5 responses are considered, and the results are investigated. As the results, optimal conditions those satisfy all response objects can be derived.

미세 피치를 갖는 MEMS 프로브 팁의 설계 및 기계적 특성 평가

하석재(Ha, Seok-Jae),김동우(Kim Dong-Woo),신봉철(Shin, Bong-Cheol),조명우(Cho, Meyong-Woo),한청수(Han, Chung-Soo) 한국산학기술학회 2010 한국산학기술학회논문지 Vol.11 No.4

프로브 카드는 반도체 제조 공정 전에 반도체 소자 및 필름의 기능과 성능을 검사하기 위한 테스트 장비이 다. 반도체 산업의 급속한 기술 발전과 반도체 소자의 고집적화로 인하여 반도체 소자의 패드 간격과 패드의 수가 증가하고 있다. 따라서 반도체 소자의 크기 및 배열의 형태가 계속 축소됨에 따라 미세 피치를 갖고 검사용 핀의 수 가 많은 프로브 카드가 필요하다. 본 논문에서는 수직형 프로브 카드의 적용을 위하여 MEMS 기술을 이용한 프로브 팁을 개발하였다. 프로브 팁의 설계를 위해서 유한요소해석을 이용하여 프로브 팁의 구조 및 기계적 특성에 대한 구 조설계를 수행하였다. 또한 구조 설계를 적용한 프로브 팁을 제작하여 유한요소해석의 결과와 실제 시험을 통한 접 촉력의 평가를 수행하였다. 이에 따라 피치 간격이 약 50㎛이하의 프로브 카드를 제작하였다. The probe card are test modules which are to classify the good semiconductor chips and thin film before the packaging process. In the rapid growth a technology of semiconductor, the number of pads per unit area is increasing and pad arrays are becoming irregular. Therefore, the technology of probe card needs narrow width and lots of probe tip. In this paper, the probe tip based on the MEMS(Micro Electro Mechanical System)technology was developed a new MEMS probe tip for vertical probe card applications. For the structural designs of probe tip were performed to mechanical characteristics and structural analysis using FEM(Finite Element Method). Also, the contact force of MEMS probe tip compared with FEM results and experimental results. Finally, the MEMS probe card was developed a fine pitch smaller than 50㎛.