Cost pressure on traditional LED packaging highlights COB light source may become mainstream

COB light sources were once all the rage, and their superior heat dissipation performance and low-cost manufacturing were sought after by many packaging companies. However, when everyone turned to this bracket-free packaging technology, its reliability issues such as light efficiency and lifespan could not be guaranteed, and soon, COB packaging fell into silence again.

At present , the cost of LED packaging is relatively high. In order to reduce the overall cost of LED devices, in addition to materials, a low-cost and high-efficiency packaging structure is also needed. Therefore, how to change the existing packaging structure and achieve a reasonable low packaging cost has become the most effective and direct way for the industry to increase the market penetration rate of LED lighting . COB light sources have relatively low production costs, obvious heat dissipation functions, and have the characteristics of high packaging density and high light output density. Whether it can become the mainstream of packaging has always been the focus of the industry.

According to the survey, the COB light source market is gradually "recovering", and some COB light source manufacturers have launched new related products.

"Compared with traditional LED packaging technology, COB panels have a very soft light source and have a very large market. They are a future development direction," said Wang Ruixun, chairman of Riming Technology.

According to the survey, the number of companies engaged in COB packaging in the market is gradually increasing, and some companies have achieved mass production.

Since last year, Japanese manufacturers have made great progress in COB light source technology. Many companies have begun to switch to COB packaging mode, and COB substrate materials have also been improved, from early copper substrates to aluminum substrates, and then to the ceramic substrates currently used by some companies, gradually improving the reliability of COB light sources.

In March this year, Japan's Citizen launched a multi-chip product that uses COB technology to house multiple blue LED chips in a package, achieving high heat dissipation performance and bringing COB technology to the market again. In addition, another major Japanese manufacturer, Sharp, has also achieved mass production of ceramic board COB, making it one of the few companies in Asia that can mass-produce ceramic COB light sources.

In contrast, in China, although COB light sources have experienced the pain of the last round of development, many companies continue to research and develop, and have achieved certain technical results. Li Guoping, chairman of the listed packaging company Hongli Optoelectronics , said that Hongli Optoelectronics has currently used ceramic substrates, aluminum substrates and other materials to develop COB light sources, and has already achieved mass production, the light efficiency has also been greatly improved, and the product reliability is good.

"Ceramic substrates can solve the reliability problem of COB very well, but their material cost is relatively high and has certain technical difficulties," said Wang Ruixun. According to Gaogong LED reporters, the number of domestic companies that can mass-produce ceramic COB light sources is increasing, and the application areas of their products are gradually expanding. Among them, Riming Optoelectronics' ceramic COB packaging has been mass-produced, and Shenzhen Jingland has gradually switched from traditional aluminum substrates to ceramics since last year. Last year, the sales of COB light sources alone reached 20 million yuan. In addition, a number of domestic companies such as Lantian Weiguang and Lite-On have also extended their tentacles to COB light sources.

"Currently, COB-packaged bulbs have occupied about 40% of the LED bulb market. Many Japanese and domestic companies have begun to adopt the COB packaging model, which is an inevitable trend of future development," emphasized He Wenming, chairman of Fujian Wanbang Optoelectronics Technology Co., Ltd.

In addition, COB light sources have not only improved their materials and reliability, but also their optical technology has been further improved. Although COB light sources have good heat dissipation functions, the copper foil under the substrate can only be powered well, but cannot be used for good optical processing. Therefore, some companies have proposed MCOB technology. MCOB has higher light output efficiency than COB light sources and is expected to become the mainstream in the market.

MCOB technology, namely multi-cup integrated COB packaging technology, is the abbreviation of Multi Chips On Board, which is the LED cluster packaging technology. COB technology integrates N chips together on a substrate for packaging. However, there is copper foil under the substrate, which cannot be optically processed well. MCOB directly places the chip in multiple optical cups for packaging, which improves the luminous flux and can also facilitate the packaging of LED surface light, increase the power of a single light source , minimize glare and zebra pattern, and improve the light efficiency per watt.

Cost reduction and COB packaging advantages are highlighted

In recent years, the demand for high-power LED packaging has gradually moved towards thinner and lower-cost, and COB light sources are favored by the market for their advantages such as low cost, ease of application and diverse designs.

According to the research report of Gaogong LED Industry Research Institute , the rapid expansion of Japan's LED bulb market in 2010 has become a typical example of global LED lighting. At present, Japan's LED bulb market is mainly based on COB multi-crystalline packaging, while traditional high-power chips and modules are mostly used for directional LED light sources such as MR16.

"Compared with traditional LED SMD chip packaging and high-power packaging, COB packaging can directly package multiple chips on the metal-based printed circuit board MC PCB , and directly dissipate heat through the substrate, which can not only reduce the manufacturing process and cost of the bracket, but also has the heat dissipation advantage of reducing thermal resistance," said Xie Jian, chairman of Nantong Kaiyu Lighting Technology Co., Ltd. In addition to reducing the use of brackets, COB can also omit some processes while maintaining product quality. Xie Jian further pointed out, "At present, some companies directly use the lamp cup of the downlight as a heat sink without adding a heat sink. SMD packaging requires reflow soldering when performing patching, and its high temperature causes significant damage to the chip. However, COB packaging does not require reflow soldering, so there is no need to purchase patch machines and welding equipment, which not only lowers the threshold for application companies, but also reduces costs."

COB packaging can save costs in many ways. Take a 25W LED as an example. Traditional high-power 25W LED light sources must use 25 1W LED chips to package into 25 LED components, while COB packaging packages 25 1W LED chips into a single chip, so the required secondary optical lenses will be reduced from 25 to 1, which helps to reduce the light source area, reduce materials and system costs, and thus simplify the secondary optical design of the light source system and save assembly labor costs.

The reduction in costs has made the market price of COB light sources lower than that of SMD patches and high-power integrated packages. "Since multiple chips share one substrate, multi-wattage lamp beads save costs and the market price is much cheaper," said Xie Jian.

Can COB packaging become mainstream despite concerns about reliability?

At present, there is little demand for COB integrated packaging from application companies. Due to the failure of the previous round of investment, many lighting application companies dare not use this packaging. "In addition to good heat dissipation performance and low cost, COB light sources can also be personalized, which is one of the leading directions of future packaging development," said Tang Liangfa, deputy general manager of Shenzhen Jingland.

However, there are not many packaging companies that can mass produce COB light sources in the market, and most of them use aluminum substrates as materials. "The bottleneck of COB packaging technology lies in how to improve the reliability of the light source and its environmental trial degree," said Li Guoping. Currently, aluminum substrate COB is widely used in the market. Due to its large thermal resistance and low reliability, it is easy to have light decay and dead light phenomenon.

However, although ceramic substrate is one of the ideal materials for COB, it is difficult to be accepted by customers due to its high cost, especially when the power is less than 2W.

"The market is still in a wait-and-see attitude towards COB light sources, and the demand is not high. Small chips are used more, and COB packaging of large chips still has many problems such as thermal resistance and light efficiency," said a packaging technology engineer in Taiwan. Since COB reduces the light loss caused by multiple refractions of a primary optical lens, there is still room for improvement in light efficiency and heat energy increase, and the production yield of the substrate also needs to be improved.

"At present, there are still standardization issues for COB light sources. The standards of packaging manufacturers and lighting finished product factories cannot be aligned, which has led to an embarrassing situation in which there is little demand for COB light sources in the market," a technical engineer who has worked at ...

It is understood that COB light sources mainly depend on eutectic technology, bracket materials and flip-chip technology. However, currently there are very few companies, including Taiwanese manufacturers, that can make high-reliability COB light sources.

LED modules are divided into various structural forms such as COB light source and vertical light source. International manufacturers such as Cree, Osram , and Philips have taken the path of vertical light source modules and have achieved breakthroughs in white light RGB.