LED lamp design ideas: reducing chips

Reduce costs by reducing chip count

After removing the LED bulb cover, the LED package is what is in front of us (Figure 4, Figure 5). The LED package with the LED chip is an important component that determines the light quality, and is also the "most expensive part of the LED bulb" (most LED bulb manufacturers).

Figure 4: Disassembly of Group A LED bulbs (click on the image to enlarge)

Note: Toshiba Lighting Technology's 7.2W product uses COB LEDs with high luminous efficiency. Samsung LED's 7.1W product and Kingsun Optoelectronics' 7.5W product both use ordinary SMD LEDs. Recently, the number of SMD products with high luminous efficiency has been increasing, so it is no longer possible to simply assume that only COB has excellent luminous efficiency. The manufacturer names and functions of the components are speculated by this site.

Figure 5: Packaging form of group B LEDs (click on the image to enlarge)

Note: The 6W product of Royal Philips Electronics of the Netherlands is equipped with the LED "LUXEON Rebel" produced by Philips Lumen, and the LED chip size reaches 1mm square. In order to avoid thermal stress, Philips Lumen recommends that the LED be packaged in a patterned FR-4 substrate, and in fact, this substrate is used. All other varieties use aluminum LED packaging substrates.

Most of the LED bulbs from overseas manufacturers are designed with only a small number of high-power surface-mounted device (SMD) LED packages. For example, the 7W product of China Zhenmingli Holdings Co., Ltd. (Zhenmingli Holdings) and the 6W product of Royal Philips Electronics of the Netherlands only use 4 SMD packages, each of which is equipped with a large LED chip. This design is "not conducive to the uniformity of light and luminous efficiency, but has an advantage in terms of cost" (technicians who assisted in the disassembly). The reason is that the brightness can be increased by increasing the input power of each chip, reducing the number of LED chips required. However, doing so will increase the heat generated by the chip, so a corresponding heat dissipation mechanism is required.

On the contrary, Toshiba Lighting Technology's 7.2W product uses multiple small LED chips to reduce the input power of each chip, thereby improving the luminous efficiency. The company uses COB (Chip On Board) technology to directly package 96 LED chips on the substrate. Although some people believe that the cost of the LED itself will increase due to the large number of chips used, "this move can improve the luminous efficiency, not only simplify the heat dissipation mechanism, but also make it less likely to have uneven luminescence" (the company).

In addition, in this disassembly, the LED suppliers of the following four products can be inferred based on the appearance of the LED. The 7.5W product of Kingsun Optoelectronics and the 6W product of Royal Philips Electronics are estimated to be equipped with the LED "LUXEON Rebel" of Philips Lumileds Lighting of the United States. The 6W product of Kumho Electric of South Korea is estimated to be the LED of Nichia Chemical Industry, and the 7W product of Shin Ming Li Holdings is the LED of Cree of the United States.

All the LED chips mentioned above are not cheap. The technician who assisted in the disassembly said, "If we use LEDs from Taiwanese manufacturers, it will only cost half the price." Regarding this, Zhen Mingli Holdings said, "Due to patent issues, we used Cree's LEDs." It seems that manufacturers cannot just use cheap LEDs.