LED芯片封装在线非接触检测系统

根据p-n结的光生伏特效应,采用交变光源照射待测LED芯片,在封装的短路支架上激励出光生短路电流;通过对该微弱电流信号的测量,判断引脚式封装的LED芯片在压焊工艺中/后的功能状态及焊线质量,实现LED芯片的非接触检测。构建了以单片机为控制核心的测试系统,采取了提高系统检测准确性和检测效率的措施,实现了系统控制、数据处理分析等功能。实验结果表明,该系统能正确检测红光、黄光及绿光LED芯片,系统检测效率高,单个LED芯片的检测时间仅为10ms,适用于实际LED生产时引脚式封装工艺过程中的在线检测。     

LED芯片封装缺陷检测方法研究

引脚式LED芯片封装工艺中封装缺陷不可避免.基于p-n结的光生伏特效应和电子隧穿效应,分析了一种封装缺陷对LED支架回路光电流的影响.利用电磁感应定律对LED支架回路光电流进行非接触检测,得到LED芯片功能状态及芯片电极与引线支架问的电气连接情况,并对检测精度的影响因素进行分析.实验表明,该方法具有高检测信噪比,能够实现对封装过程LED芯片功能状态及封装缺陷的检测.计算结果与实验结果较好吻合.     

LED芯片在线检测方法研究

对于封装过程中的LED芯片的检测目前还没有行之有效的方法,基于p-n结的光生伏特效应和法拉第定律,提出一种非接触式的针对LED封装过程中芯片质量及芯片与支架之间连接状态的检测方法。根据实际LED芯片所处的闭合短路状态,感应回路由绕在高磁导率条形磁芯上的多匝线圈构成。磁芯采用不同搭接方式以提高检测的信噪比,根据实验结果确定了磁芯的最佳搭接方式。实验结果表明,该方法具有较高的检测精度,可以实现对闭合短路状态微安量级光生电流的检测。计算结果与实验结果吻合较好。     

基于小波分析的LED芯片非接触检测信号处理

针对现有LED芯片非接触在线检测系统中存在信号处理方法简单、检测信号信噪比低等问题,本文分析了系统噪声并讨论了处理方法,研究了小波变换对LED非接触检测信号进行消噪的原理和实现过程,对检测信号进行了小波消噪的仿真和实验,并分析了结果数据。实验结果表明,小波分析在LED非接触检测信号消噪中的应用能够有效提高信噪比并切实可行。     

LED芯片封装工艺中焊接缺陷研究

介绍了发光二极管（LED）封装工艺中常见焊接缺陷与可能存在的危害。对污染物造成的焊接缺陷作了具体研究,理论分析了因缺陷引入的接触电阻和隧道电阻,测量了正常情况和缺陷焊接时LED的光谱和光生电流,并提出了存在缺陷焊接的LED的等效电路,对实验结果进行了分析。结果表明：LED发生焊接缺陷时的发光强度、光生电流明显比正常情况小,可以通过测试LED芯片的发光强度或光生电流达到检测LED焊接缺陷的目的。该研究对提高LED封装的可靠性和提出检测LED焊接缺陷的方法具有重要意义。     

LED芯片检测系统的噪声分析及信号处理研究

分析了LED芯片非接触检测系统噪声信号的功率谱,研究了噪声信号的抑制方法.针对现有检测系统存在检测信噪比低的不足,提出对交变电压信号进行相关检测,采用相关检测后,检测系统的信噪比可以提高20 dB以上.实验结果与仿真结果吻合.该研究对于改进检测系统的性能以满足对多种芯片的正确检测有重要意义.     

基于PSoC的瞳孔光刺激与测量系统

瞳孔跟随光刺激的变换检测系统可广泛用于疲劳检测、颅内损伤检测等方面。为实现方便可控的刺激光源生成和光强检测,设计实现基于PSoC（Programmable System on Chip,片上可编程系统）芯片的光刺激与测量系统。以PWM（脉冲宽度调制）的方式驱动LED,PC端设计了应用控制界面,可以调节LED光照刺激的强度频率等参数,并实时获得光强数据。系统实际运用于实时瞳孔参数检测平台,提供稳定可控的光刺激与测量功能。     

基于多芯光纤束的轧辊磨损度检测系统

针对板带热轧领域中的轧辊磨损度检测问题,提出了基于多芯光纤束的轧辊磨损度检测系统。在该系统中,多芯光纤束固定在距离轧辊一定距离的支架上,对激光信号进行发射和接收,实现轧辊磨损度光信息的传输。此系统不仅实现了轧辊磨损度的非接触高精度测量,还可以提高轧辊磨损度检测的智能化水平。     

线阵CCD单板旋切厚度在线测量系统

线阵CCD作为一种高灵敏度光电传感器,广泛用于非接触检测领域中.本文介绍的线阵CCD单板旋切厚度在线测量系统,以8031单片机为核心,实现对单板旋切厚度的非接触在线测量,通过LED显示器显示测量结果.并由打印机隔时打印.测量精度达±1.4μm.该系统具有速度快、精度高、对环境要求低等特点.     

基于DSP的疲劳驾驶预警系统的设计

本文描述了一个基于TI公司高速图像处理芯片TMS320DM642的疲劳检测预警系统,用以判定驾驶员的疲劳程度,降低交通事故.本系统采用非接触方法,先通过CCD摄像头拍下驾驶员的面部图像序列,然后检测出脸部,从而定位眼睛,再利用PERCLOS判定疲劳状态.本系统还结合免费的开源计算机视觉库OpenCV来加快开发速度和降低开发成本.     

Flaw detection of domed surfaces in LED packages by machine vision system

Epoxy-packaging is widely used in light-emitting diode (LED) packages to protect LED chips and magnify the chip light. Surface flaws in LED packages affect not only the appearances of LEDs but also their functionality, efficiency and stability. Due to the high demand for productivity and quality, bare-eye-inspection approach becomes extremely inadequately. Therefore, this research proposes a machine-vision-based system for detecting tiny flaws occurred in the domed surfaces of LED epoxy-packing. We apply grey relational analysis to the frequency components in block discrete cosine transform domain, and significantly attenuate the large-magnitude frequency components that represent the background texture of the surface based on their corresponding grey relational grades. Then, by reconstructing the declined frequency components, we eliminate not only random texture but also uneven illumination patterns and retain anomalies in the restored image. This approach overcomes the difficulties of inspecting tiny flaws from uneven illumination backgrounds. Experimental results show that the proposed method can effectively inspect tiny flaws in LED domed surfaces.     

Development of reel-to-reel microchip mounting system for fabrication of meter-long LED lighting tapes

We have developed a reel-to-reel microchip mounting system that continuously mounts LED chips and other microchips on meter-long flexible printed circuit board (PCB) tape for 1.2-m-long standard LED light tubes. Mounting microchips on meter-long PCBs is difficult because a large chip mounter is expensive and the chip positioning stage is difficult to move in a meter-wide area with an accuracy of hundreds of micrometers. Hence, we developed a new microchip mounting system that utilizes a small chip mounter and reel winding machines. The system repeatedly moves the long PCB tape by a certain length with the reel winding machines and mounts the chips on it. The PCB tape (which is 5 mm wide) is made by fabricating long PCB tapes which are 25 cm × 26.6 m through a roll-to-roll PCB process and slitting them into meter-long tapes. The reel-to-reel system repeatedly mounts chips by adjusting their positions through image processing of the copper wiring pattern on the PCBs. Our constructed system mounted 24 LED chips with a pitch of 5 cm with an accuracy of 0.082 mm to form a 1.2-m-long LED tape. The luminance of the tape is 12.4 lx at a distance of 1 m, which is the luminance of outdoor corridor lighting. Therefore, this system can be used for meter-long tape lighting.     

基于视觉伺服的LED芯片形状匹配算法研究

LED芯片的定位是LED芯片检测、分选等后封装过程的关键步骤,其定位速度和精度直接决定了LED芯片检测设备的生产效率。为了提高芯片定位的精度,提出了基于视觉伺服的反馈补偿技术,有效补偿了芯片定位误差;为了提高芯片定位的速度,在视觉伺服系统的基础上,针对LED芯片的特点,提出形状匹配优化算法,通过减小匹配过程中匹配的面积和搜索的角度,有效弥补了因视觉运动补偿所消耗的时间。通过以上两方面提高了LED芯片定位精度和速度,满足LED芯片高精和高速的定位需求。     

Error analysis based on error transfer theory and compensation strategy for LED chip visual localization systems

Journal of Intelligent Manufacturing - In the manufacturing process of LED chips, the accuracy of the LED chip visual localization system affects the quality of LED chip production directly. There...     

Manufacturing and packaging of sensors for their integration in avertical MCM microsystem for biomedical applications

Demonstrates the feasibility of integrating fragile micromachined chips into a complex three-dimensional (3-D) multichip module (MCM) microsystem for a biomedical application. The system is based on the vertical integration of the different parts: micropumps and valves, a multisensor chip for on-line control of the system and a signal-processing chip. In this paper, packaging of the microsystem is studied in order to minimize the induced stress that can affect the integrity of the different micromachined parts of the system. Standard commercially available components and materials were used so as to minimize costs for the case of high volume packaging. For testing the approach, a multisensor chip which includes thin silicon membrane-based devices has been used as the main test structure to compare different packaging materials. In addition, for the fabrication of such a sensor chip in an efficient mode, technological modules needed to fabricate sensors on complementary metal-oxide-semiconductor (CMOS) wafers are discussed. The definition of standardized "add-on" sensor modules to the CMOS process of a foundry is intended to limit the development cost of smart sensors