Seok-Jae Ha

머신비전에 의한 LED Chip Package 형광물질 토출형상 측정

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.

Process Capability Optimization of a LED Die Bonding Using Response Surface Analysis

Abstract 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. Key Words : LED chip package, Die bonding(or attaching), Design of experiment, Response surface analysis 본 논문은 지식경제 기술혁신사업(신성장동력장비경쟁력강화사업)의 일환으로 수행중인 ‘LED 패키지 In-line 자동화 시스템 개발’ 과제 연구비 지원으로 수행되었음. * Corresponding Author : Seok-Jae HaTel: +82-11-9092-2753 email: sjha1103@gmail.com접수일 12년 07월 31일 수정일 (1차 12년 08월 22일, 2차 12년 09월 14일, 3차 12년 09월 27일) 게재확정일 12년 10월 11일 1. 서론 LED 칩의 일반적인 패키징 공정은 웨이퍼에 형성된 칩의 양부를 검사하는 웨이퍼 검사 공정, 웨이퍼를 절단하여 낱개로 분리된 칩을 리드 프레임(lead frame)에 부착시키는 다이 본딩(die bonding) 공정, 다이에 구비된 접촉 패드와 리드 프레임의 리드를 와이어로 연결시키는 와이어 본딩(wire bonding) 공정, 다이의 내부회로와 그 외의 구성 부품을 보호하기 위해 봉지재로 외부를 감싸는 몰딩(molding) 공정, 리드와 리드를 연결하고 댐바(dam bar)를 절단하는 트림 공정 및 리드를 원하는 형태로 성형시키는 포밍(forming) 공정을 거치게 된다. 그중에서 다이 본딩 공정은 분할된 칩(die)이 이후 공정에서 견딜 수 있는 충분한 강도의 접착력을 갖도록 칩을 고정시키고 칩으로부터 발생하는 열을 방출시키기 위해 적절한 열전도도 및 전기전도도를 부여하는데 있어 매우 중요한 공정이며, 통상적인 다이 본딩 공정순서를 그림 1에 나타내었다[1,2].

Assessment of Design and Mechanical Characteristics of MEMS Probe Tip with Fine Pitch

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㎛.

Development of Dispenser System with Electrohydrodynamic and Voice Coil Motor for White Light Emitting Diode

LED(Light Emitting Diode) is used in various filed like a display because of low power consuming, long life span, high brightness, rapid response time and environmental-friendly characteristic. General fabrication method is combination blue light LED chip with yellow fluorescent substance. Because this way is suitable for industry field in terms of convenience, economic, efficiency. In white light LED packaging process, encapsulation process that is dispensing fluorescent substance with silicon to blue light LED chip is most important. So, in this paper we develop EHD pump system using voice coil motor and electrostatic pump for dispensing fluorescent substance. For these things we conduct basic test about liquid surface profiles by voltage and process time. Through this data we decide optimal process condition and verify the optimal condition using design of experiment method. And to confirm uniformity of the condition, we conduct repeat dispensing test.

LED Die Bonder Inspection System Using Integrated Machine Visions

In LED chip packaging, die bonding is a very important process which fixes the LED chip on the lead flame to provide enough strength for the next process. During the process, inspection processes are very important to detect exact locations of dispensed epoxy dots and to determine bonding status of dies whether they are lies at exact positions with sufficient bonding strength. In this study, a useful machine vision based inspection system is proposed for the LED die bonder. In the proposed system, 2 cameras are used for epoxy dot position detection and 2 cameras are sued for die attaching status determination. New vision processing algorithm is proposed, and its efficiency is verified through required field experiments. Measured position error is less than X:-29㎛, Y:-32㎛ and rotation error:3° using proposed vision algorithm. It is concluded that the proposed machine vision based inspection system can be successfully implemented on the developed die bonding system.

Analysis of Polishing Mechanism and Characteristics of Aspherical Lens with MR Polishing

The aspherical lens was designed to be able to array a focal point. For this reason, it has very curved surface. The aspherical lens is fabricated by injection molding or diamond turning machine. With the aspherical lens, tool marks and surface roughness affect the optical characteristics, such as transmissivity. However, it is difficult to polish free form surface shapes uniformly with conventional methods. Therefore, in this paper, the ultra-precision polishing method with MR fluid was used to polish an aspherical lens with 4-axis position control systems. A Tool path and polishing mechanism were developed to polish the aspherical lens shape. An MR polishing experiment was performed using a generated tool path with a PMMA aspherical lens after the turning process. As a result, surface roughness was improved from

Development of Abrasive Film Polishing System for Cover-Glass Edge using Multi-Body Dynamics Analysis

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Indirect cutting force measurement in the micro end-milling process based on frequency analysis of sensor signals

In recently, the demand of cover-glass is increased because smart phone, tablet pc, and electrical device has become widely used. The display of mobile device is enlarged, so it is necessary to have a high strength against the external force such as contact or falling. In fabrication process of cover-glass, a grinding process is very important process to obtain high strength of glass. Conventional grinding process using a grinding wheel is caused such as a scratch, chipping, notch, and micro-crack on a surface. In this paper, polishing system using a abrasive film was developed for a grinding of mobile cover-glass. To evaluate structural stability of the designed system, finite element model of the polishing system is generated, and multi-body dynamic analysis of abrasive film polishing machine is proposed. As a result of the analysis, stress and displacement analysis of abrasive film polishing system are performed, and using laser displacement sensor, structural stability of abrasive film polishing system is confirmed by measuring displacement.