As a supplier of high-power LED products, CREE is undoubtedly the leader in technology growth and market share. Since the launch of the first COB product in 2011, the introduction of XLAMP CXA2 LED array products has gradually recognized the market for its COB products. I just have a question: CREE is a company with SiC technology as its core technology. Is there any essential difference between its COB and other homes? Or what is the core technology of its COB products? Let's take a look at the performance of the CAX1820 product:
First, the appearance and lighting pictures
1, cofferdams are more joints
Not beautiful. This causes the joint to be caused by too much glue at the start and end points. If you want to overcome, there are ways. CREE does not seem to pay close attention to the problem here, gradually increase the amount of glue at the starting point to the normal amount, and gradually reduce from the normal amount at the end.
2, temperature test point
Temperature test point: not true. If the temperature is measured as a reference for the chip temperature, it is not true. Since this is not the same plane as the chip's die plane, there is a temperature difference. The temperature test point is located on the BT board and the chip is mounted on the underlying ceramic substrate.
3, circle shaped shadow
Circle shadow: not beautiful. This phenomenon is caused by the fact that the COB is made of two kinds of sheets. The upper layer material is a hollow region in the middle of the BT plate to form a light-emitting area, and the edge of the circle is used for line production. The lower layer is a ceramic substrate. The intermediate layer is formed by film pressing for hot pressing.
Small current lighting picture
Through a small current lighting test, it was found that there are 60 chips inside, 12 strings and 5 pairs. The gold wire is used between the chips, and the chip at the two ends is connected to the circuit on the PCB. The surface of the circuit is treated with immersion gold. The purpose is to weld better with the gold wire, and the gold is not vulcanized.
The arrangement of the chips also tends to be circular, so that the overall luminous pattern is rounded. Why is it 12 strings? At present, most of the COB products, whether CREE or PHILIPS, use 12 strings and the voltage is about 37. The reason is that the company that started the large-scale promotion of COB products with a voltage of 37V is Japan's CITIZEN, and everyone is now imitating it.
Through the side view, it was found that there are two layers of different materials. The upper layer is a BT sheet and the lower layer is a ceramic substrate.
Second, the performance test
In the specification, the parameters are described as follows (@550mA):
The actual test data is as follows (2700K R4 file Ra 80)
The color rendering index and color tolerance are very well controlled, but the luminous flux does not reach the nominal value. The CREE specification mentions that the error range of the luminous flux is 7%, but this sample is even lower than the lower limit and then 7% lower, or the optical pass is unqualified, the device difference is really big. From 300 mA to 700 mA, the X value is offset by about 0.006 and the Y value is offset by about 0.004.
Look at the spectral curve again:
It was found by spectroscopy that blue light chips + yellow-green and red phosphors were used to form white light. A fine red phosphor was found after actually peeling off the fluorescent gel.
Third, the chip
Through the test data, we can find that the data is at a medium level. Then let's see who is using the chip? Remember the cooperation between CREE and Taiwan Ronda last year? One of its purposes is to ensure the supply capacity of small and medium power chips. Through anatomy, the chip is more in line with the general practice of Taiwan's chip factory, so it is suspected that its chip is provided by Taiwan's Ronda.
Through the process of peeling off the glue, it was found that the encapsulant was silica gel and the bonding ability with the ceramic substrate was good. However, the chip is easy to push, and it is speculated that the solid crystal glue is used as a silicon-based glue.
Fourth, dismantling
The sample was placed in a container filled with aqueous red ink, and the container was placed on a heating platform for heating at a heating temperature of 90°. After 2 hours, the upper BT plate was cut and the red ink intrusion mark was found from the joint surface of the BT plate and the ceramic substrate.
If this product is subjected to long-term thermal shock, it will cause serious signs of intrusion.
Fifth, the application
What product is COB product to use? There are advantages in downlights such as downlights, track spotlights, and PAR lights. Tube Lights and Bulbs These lamps with low power and large illuminating area are not suitable for COB products.
CREE's COB products are also expected to be used in commercial lighting fixtures, so the light-emitting surface is made smaller and facilitates optical design. Strict control of light color quality, 3 step ellipse and 85 ° temperature sorting, is also determined for the commercial lighting market.
Summary
Through testing and dismantling, it was found that the COB supply and raw materials are common products in the market. There are no unique new technologies. What is its core technology? What about CREE SiC?
Which COB technology is strong, CREE is really very general. Is there a product without SiC technology or a CREE product? The purchase of Taiwanese chips and even the domestic Dehao, Sanan chips are available to domestic packaging factories, domestic companies can also make the same performance products, and the price is cheaper than CREE. COB technology has done a good job in several early domestic companies. For example, Wuhan Changjiang, Ningbo Shengpu, Guangzhou Silicon Energy and Huizhou Leitong personally feel that they are still trustworthy.
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