Enhancement of the Optical Performances for the LED Backlight Systems with a Novel Dual Lens-Cap

2007 ◽  
Vol 364-366 ◽  
pp. 132-137
Author(s):  
Paul C.P. Chao ◽  
Lun De Liao ◽  
Chi Wei Chiu ◽  
Chien Yu Shen
Keyword(s):  
Light Source ◽  
Printed Circuit Board ◽  
Circuit Board ◽  
Dual Cone ◽  
High Brightness ◽  
Light Emitting ◽  
Lower Power ◽  
Printed Circuit ◽  
High Uniformity ◽  
Led Backlight

A novel dual-cone-shaped side-emitting lens cap for High Brightness Light Emitting Diodes (HB-LEDs) is proposed for improving brightness and high uniformity of the direct LED backlight Units (BLUs) for large-sized LCD-TVs. Combining the designed lens cap with red, green and blue (RGB) chips on a Metal Core Printed Circuit Board (MCPCB), the LED module with the proposed cap is able to provide a compact white light source with unique features such as instant color variability and lower power usage, etc. The dual-cone-shaped of the proposed lens cap is designed to emit most of the light rays to the sides, only a small portion of light upward along the optical axis of the lens, providing a uniform luminance distribution and the high brightness on the backlight. In addition, a small reflective surface in semi-circular shape is designed and placed upon the proposed LED module about 10mm, the surfaces of which are attached with reflective films to increase the level of light mixing in the larger, global reflector optical box. With the structure of the LED module well designed, the LED backlight Module would be designed for the large-sized LCDTV using the fewer number of LEDs to lead to lower power consumption. The results indeed identify the attributes of the BLU, which make it possible to achieve excellent backlight performance using a direct illumination approach from the light source of “Dual-Cone-Shaped Side- Emitting Lens Cap of LEDs.”

Temperature and Humidity Dependent Reliability Analysis of RGB LED Chips

2006 ◽  
Author(s):  
Jun-Xian Fu ◽  
Shukri Souri ◽  
James S. Harris
Keyword(s):  
Reliability Analysis ◽  
Printed Circuit Board ◽  
Light Emitting Diode ◽  
Circuit Board ◽  
Light Emitting ◽  
Printed Circuit ◽  
Root Cause ◽  
Micro Cracks ◽  
Temperature And Humidity

Abstract Temperature and humidity dependent reliability analysis was performed based on a case study involving an indicator printed-circuit board with surface-mounted multiple-die red, green and blue light-emitting diode chips. Reported intermittent failures were investigated and the root cause was attributed to a non-optimized reflow process that resulted in micro-cracks and delaminations within the molding resin of the chips.

PENGARUH DIMENSI GEOMETRIK LAMPU LED TERHADAP PERSEPSI KECERAHAN

2013 ◽  
Vol 3 (2) ◽  
pp. 41
Author(s):  
Andrea Marisi ◽  
Revantino Revantino
Keyword(s):  
Solid State ◽  
Printed Circuit Board ◽  
Light Emitting Diode ◽  
Circuit Board ◽  
Solid State Lighting ◽  
Light Emitting ◽  
Printed Circuit ◽  
Surface Mounting

Perkembangan teknologi di bidang Solid State Lighting selama dekade terakhir membuat diversifikasi penggunaan Light Emitting Diode untuk pelayanan pencahayaan umum. Balai Besar Bahan dan Barang Teknik sejak tahun 2011 telah melakukan penelitian dan pengembangan lampu LED berbasis Surface Mounting Device (SMD) 5050. Pada perancangan Printed Circuit Board (PCB) untuk memasangkan LED-smd tersebut, dilakukan analisis dimensi geometrik yang optimal sehingga dapat memancarkan cahaya ke segala arah dan memberikan persepsi kecerahan yang lebih baik. Untuk perancangan PCB tersebut, dipilih 2 (dua) model berbentuk silinder dengan memperhatikan rasio antara tinggi dan diameter alas. Dari pendekatan sumber titik dan perhitungan eksitansi luminus, diperoleh bahwa model dengan rasio ≈ 1 menghasilkan persepsi lebih cerah terhadap visual manusia.Kata kunci : dimensi geometrik, pendekatan sumber titik, eksitansi luminus, persepsi kecerahan

A Solder Joint Reliability Model for the Philips Lumileds LUXEON Rebel LED Carrier Using Physics of Failure Methodology

2013 ◽  
Vol 2013 (1) ◽  
pp. 000887-000892 ◽  
Author(s):  
Rudi Hechfellner ◽  
Michiel Kruger ◽  
Tewe Heemstra ◽  
Greg Caswell ◽  
Nathan Blattau ◽  
...  
Keyword(s):  
Solder Joint ◽  
Printed Circuit Boards ◽  
Printed Circuit Board ◽  
Light Emitting Diodes ◽  
Coefficient Of Thermal Expansion ◽  
Thermal Control ◽  
Circuit Board ◽  
System Level ◽  
Light Emitting ◽  
Printed Circuit

Light Emitting Diodes (LEDs) are quickly evolving as the dominant lighting solution for a wide variety of applications. With the elimination of incandescent light bulbs and the toxic limitations of fluorescent bulbs, there has been a dramatic increase in the interest in high-brightness light emitting diodes (HB-LEDs). Getting the light out of the die, with reliable color, while maintaining appropriate thermal control over a long service life is a challenge. These issues must be understood and achieved to meet the needs of unique applications, such as solidstate-lighting, automotive, signage, and medical applications. These applications have requirements for 15–25 years of operation making their reliability of critical importance. The LUXEON Rebel has been accepted as an industry leading LED product, widely used in Mean-Time-Between-Failure (MTBF) sensitive applications. Customers use various mounting platforms, such as FR4 Printed Circuit Board (PCB), FR4 PCB with thermal via's, Aluminum & Copper Metal Core printed Circuit Boards (MCPCB), Super MCPCB, etc. As in other LEDs, when mounting to a platform where a large Coefficient of Thermal Expansion (CTE) exists between the LED & the PCB, Solder fatigue could become an issue that may affect system level lifetime. In this paper we have examined extreme cases and how a solder joint can impact system level reliability. We have modeled the conditions and formed a means to predict system level reliability. We have compared the prediction modeling with empirical tests for validation of the models. It is vital to understand system level reliability factors to build lighting solutions that match the application and customer expectations. It is impractical to test LEDs and other components for 50k hours ~5 years since the device evolution is much faster than that – on average one LED generation every 12–18 month. Hence we need models and prediction methods …..

scholarly journals Machine vision based in-process light-emitting diode chip mounting system

2018 ◽  
Vol 51 (7-8) ◽  
pp. 293-303 ◽  
Author(s):  
Chao-Ching Ho ◽  
You-Min Chen ◽  
Po-Chieh Li
Keyword(s):  
Machine Vision ◽  
Printed Circuit Board ◽  
Vision System ◽  
Light Emitting Diode ◽  
Circuit Board ◽  
Robot Arm ◽  
Light Emitting ◽  
Printed Circuit ◽  
Delta Robot ◽  
A Charge

Background: In this study, a machine vision–based method was developed for automated in-process light-emitting diode chip mounting lines with position uncertainty. In order to place the tiny light-emitting diode chips on the pattern of a printed circuit board, a highly accurate mounting process is achieved with online feedback of the visual assistance. Methods: The system consists of a charge-coupled device camera, a six-axis robot arm, and a delta robot. The lighting system is a critical point for the in-process machine vision problem. Hence, designing the optimal lighting solution is one of the most difficult parts of a machine vision system, and several lighting techniques and experiments are examined in this study. In order to commence the mounting process, the light-emitting diode chip targets inside the camera field were identified and used to guide the delta robot to the grabbing zone based on the calibrated homography transformation. Efforts have been focused on the field of machine vision–based feature extraction of the chip pins and the holes on the printed circuit board. The correspondence of each other is determined by the position of the chip pins and the printed circuit board circuit pattern. The image acquisition is achieved directly online in real time. The image analysis algorithm must be sufficiently fast to follow the production rate. In order to compensate for the uncertainty of the light-emitting diode chip mounting process, a visual feedback strategy in conjunction with an uncertainty compensation strategy is employed. Results: Finally, the light-emitting diode chip was automatically grabbed and accurately placed at the desired positions. Conclusion: On-line and off-line experiments were conducted to investigate the performance of the vision system with respect to detecting and mounting light-emitting diode chips.

Maker Chemistry: Exploring Redox Reactions in Introductory Laboratory through Light-Emitting Diode Printed Circuit Board Fabrication

2019 ◽  
Vol 97 (2) ◽  
pp. 490-496
Author(s):  
Scott L. Wallen ◽  
Jaspreet Dhau ◽  
Robert Green ◽  
Laura B. Wemple ◽  
Troy Kelly ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Printed Circuit Board ◽  
Light Emitting Diode ◽  
Circuit Board ◽  
Light Emitting ◽  
Printed Circuit

Thermal Investigation and Placement Design of High-Brightness LED Array Package on PCB for Uniform Illuminance

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
K. C. Yung ◽  
H. Liem ◽  
H. S. Choy ◽  
W. K. Lun
Keyword(s):  
Surface Temperature ◽  
Printed Circuit Board ◽  
Cfd Simulation ◽  
Light Emitting Diode ◽  
Circuit Board ◽  
Heat Transfer Analysis ◽  
Significant Drop ◽  
High Brightness ◽  
Light Emitting ◽  
Led Array

This paper reports the thermal performance of a high-brightness light-emitting diode (LED) array package with a novel placement method on a printed circuit board (PCB). The precise heat transfer analysis and modeling using computational fluid dynamics (CFD) were performed according to the practical working conditions of the LED array. Emphasis was placed upon investigating how the temperature of the surface of LEDs changed in accordance with different placement methods. A significant drop in the surface temperature of the LEDs was found when the triangular and arithmetic spacing placement methods were used; hence, the overall heat dissipating capability of the LED array to the PCB was improved. By optimizing the placement design, the average surface temperature of the LED array achieved a decrease of about 20%, from 120°C to 100°C. The illuminance level of each placement design was measured and compared. Both CFD simulation and experimental results are provided to demonstrate the efficacy of the proposed approach for LED array thermal management.

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