Components | CoB LEDs | Jul 18, 2017

Yuji LED Introduces World’s Highest Lumen Density COB Series

After years of research and development, Yuji LED proudly presents their high CRI high reliability COB with the world’s highest lumen density: A chip on board (COB) light source has a small emitting surface (LES) and large luminous flux, thus it is usually used in directional lighting fixtures, and is always the best choice for minimizing the fixture’s size. This means, however, that more heat will be generated, the luminous efficiency will be largely compromised, and that it may lead to the failure of the COB. Hence, when designing a COB, it is always the key point to improve the luminous flux and the reliability while controlling the LES. Based on this principle, YUJILEDS High Lumen Density High CRI COB Series was developed.

With an LES diameter of only 19 mm, this COB can achieve a luminous flux of 24000 lm at 5600 K, which is a luminous flux density of 88 lm/mm². Compared to 76 similar products by 15 well-known manufacturers on the market, YUJILEDS COB has an overwhelming advantage of 60 lm/mm² than the average. That is to say, when emitting the same amount of luminous flux, YUJILEDS COB has an LES only one fourth the size of other products. That creates large space for further optic design.

To tackle the heat dissipation issue, a flip chip structure and eutectic welding technology are adopted in our High Lumen Density High CRI COB, where the chip is soldered directly onto the substrate. In this way, the heat can be transferred directly to the substrate, and the efficiency can be largely increased. Second, this YUJILEDS COB has AlN substrate with a heat transfer efficiency as high as about 300 W/(m∙K), which is two times that of Al substrate, and six times that of Al2O3 substrate.

Additionally, the unique chip alignment design of YUJILEDS COB ensures that the heat is dissipated equally from the chip to the substrate, thus improving the reliability of the product. Our full power burn-in test on samples of three different color temperatures shows, after 6000 hours, the average decay of the examples is less than 1.5%, and the estimated total lifespan (L70) is over 70000 hours.

For white LEDs using the “phosphor excited by blue light” solution, the color rendering performance is decided by three factors: the phosphor properties, the mixing ratio of the phosphors and the packaging process technology. These are especially important for high lumen products, because the excited phosphor also produce large amount of heat. Yuji developed the post-treatment process, successfully improving the thermal reliability of the phosphors. Then a unique packaging technology was adopted, by which the heat is efficiently dissipated through the chip and the encapsulant. Statistics proves extremely high color rendering ability and high reliability of this COB. It has a CRI (Ra) as high as 95 even at a CCT of 5600 K. Besides, after 6000 hours of burn-in test, the product shows a color temperature shift smaller than ±50K, and the chromaticity shift is less than ±0.001.

To meet the light requirements of different places, the YUJILEDS High Lumen Density High CRI COB Series also released another member, which has an LES diameter of 9 mm and luminous flux of 6000-8000 lm. In the near future, Yuji plans to offer more choices, including a 6 mm diameter product with 3000 lm flux and a 30 mm one with 60000 lm flux.

As an LED light source manufacturer, Yuji LED always focuses on light quality, and has been dedicated to the research and production of high CRI packaged LEDs since it was founded. In recent years, apart from CRI performance, Yuji has expanded its spectrum to take design into consideration, trying to provide more possibilities and convenience for downstream manufacturers. The latest High Lumen Density High CRI COB Series was born to actualize this idea.

For more information about this COB series, please visit:

About Yuji International:

Yuji International is a manufacturer of LED phosphor material, packaged LEDs and lighting solutions. We focus on light quality, color rendering performance and custom design. We manufacture LED products for specialty applications demanding full or specialized spectrum. We welcome custom designs ranging from specialized spectral requirements to complex PCB designs, and have knowledgeable sales and engineering staff who will gladly help with any kind of project.
We are headquartered in Beijing, China, and have our offices in Sunnyvale, USA and Tokyo, Japan. For more information, please visit


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