Manufacturers of solid-state lighting are exploring the packaging substrate, type and composition to achieve a perfect balance in price / performance. If you ask the general public to draw a light-emitting diode (LED) picture, it is likely that you will still see two feet used as LEDs for instrument display. However, the LED packaging technology that illuminates small displays and computers has greatly evolved, and it is probably not recognized by the public as it is lined with the ancestors of the past. Today, LED is facing the third wave of growth cycle, and the increase in its benefits will depend on the demand for general lighting, so packaging technology needs to be more cost-effective. Of the total cost of packaged LEDs, the packaging step alone accounts for 45% (Figure 1). It is not surprising that this step has become the focus of the industry. Yole Developpement believes that the industry wants to further increase the illumination per unit cost, there are two ways to achieve this-increase the performance of each packaged product, in order to reduce the number of products at the system level, or reduce the cost per unit. Yole pointed out that LED manufacturers have never worked so hard to drive down costs because the need to increase the illumination per unit cost has changed the design philosophy of high-power products. Until last year, Yole observed that in most cases, LED manufacturers strive to increase product performance and product complexity, but now, some manufacturers focus on design methods to reduce costs when packaging products. One noteworthy example of this transition is Cree, headquartered in Durham, North Carolina, which places LED chips in packages. In the past, the design trend of many high-power LED manufacturers was to use vertical LEDs. The epitaxial or silicon carbide (SiC) substrate has been removed, and the LED structure has been connected to another carrier wafer. Cree's high-power LEDs use this design structure. Cree's latest XLamp high-brightness LED XB-D product line was launched in January 2012, returning to the simple method of the previous product-Flip-chip packaging. This product only uses the flip-chip technology that can maintain the original substrate. Cree thinned the SiC epitaxial substrate and subjected the surface treatment (Texturing) on ​​the back to increase the light extraction efficiency. Surface treatment of substrates is not a new technology. Many manufacturers use patterned sapphire substrates (PSS), but Cree uses a simpler and cheaper design. The company uses mechanical saw-like tools to create grooves on the substrate. The angle of these grooves maximizes the efficiency of light extraction. This approach is not only cheap, it also seems to be extremely efficient in generating and emitting light sources, which is a smart design in increasing the illumination per unit cost. With the exception of Cree, other manufacturers, such as Osram and Philips, want to increase cost-effectiveness, but their methods are different. Osram still uses the vertical LED structure, Philips still prefers thin film flip chip, but they also removed the sapphire crystal, Cree uses different flip chip wiring technology. Although Philips uses bump technology, Cree uses low-temperature melting crystals to further reduce costs and improve contact thermal resistance. To date, Yole has not observed standardized manufacturing methods. Figure 1 LED lighting cost analysis TV LED production capacity releases mid-power LED cost drop Before general lighting, LCD TV backlighting used to be the main driving force for LED sales, but the market expansion situation was not as expected, resulting in an oversupply of power LEDs in TV backplanes and a general increase in general lighting costs. Mid-power LEDs are packaged in a minimalist plastic leadless chip carrier (PLCC). In addition to replacing the inherent fluorescent tubes that must be more dispersed and multi-angle and multi-source, Yole believes that these mid-power LEDs have gradually entered the market using only high-power LEDs , Such as light bulbs or spotlights. The benefits of inadvertently inserting willows show that manufacturers ’strategies of making certain types of components into different related products are very beneficial to them. First of all, in the field of LED TV, the specifications of the packaged products have been standardized, which is very rare in the LED industry, this move can make the economy larger. Because the LCD TV market is not as strong as expected, a large amount of production capacity has been invested in oversupply of medium-power LEDs, which has further reduced the cost. For some applications, the price per illuminance has become very attractive. Cost-effectiveness considerations also affect the ways in which LED manufacturers meet the needs of users with different light colors. The demand for warmer light has led the industry to look for technologies other than Yttrium Aluminium Garnet (YAG), which are widely used in the industry. Manufacturers try to replace some of the cool white light produced by gallium nitride (GaN) emitters with yellow to replace YAG (Figure 2). Yole believes that YAG and its silicon substrate are still the primary form of packaging. However, with the diversified services of the industry, the need to adjust the height of various colors has emerged. Figure 2 Development schedule of phosphors To achieve this goal, manufacturers have added red elements to light colors in two ways. First, at the system level, manufacturers can add red LED chips containing YAG phosphors to standard blue chips. Cree uses this method and calls the method "TrueWhite" technology, which is also used by Osram. Another method is to add red light, mostly phosphors containing nitrides. This approach can be adjusted depending on the application, but for high-brightness LEDs, if red light is to be emitted, the production of this phosphor is very important. The problem is that nitride phosphors are still extremely expensive and difficult to manufacture. In some cases, nitride phosphors are ten to twenty times more expensive than YAG phosphors. If the user is authorized by Nichia, YAG can be used to produce yellow fluorescent powder. If not, a phosphor of silicon compound can be used. But for Hongguang, the market is dominated by Mitsubishi Chemical and its nitride phosphors. COB packaging improves cost efficiency Chip-on-board (COB) arrays are another method used by LED manufacturers to increase cost efficiency. The COB process is to use LEDs with bare crystals and connectors, and directly put them on the printed circuit board (PCB), which is mostly FR4, ceramic or metal. This can enter the module level from the bare crystal level of the supply chain. , Skip the LED packaging stage. Subsequent packaging and assembly steps, such as adding lenses, phosphors or ESD protection, are performed at the PCB level. Although skipping some steps can reduce costs, there are some costs. Although manufacturers have lower material costs and higher packaging density, the scale of COB manufacturing today is still not large enough, so the assembly cost is high. However, COB also provides technical advantages that can be converted into financial benefits. The advantage of this type of packaging technology is mainly in thermal processing. The manufacturer has less material interface on the packaging layer, and the isolation between the chip and the heat sink is also thinner. Another indirect advantage of COB is that it uses smaller crystalline particles, which also brings two advantages. First, the manufacturing yield will increase. Next, because the product is composed of many small particles, manufacturers can use a variety of products to reduce the trouble caused by the need for color mixing. Therefore, if the packaging method can be properly designed, the front-end manufacturing cost can be indirectly reduced. Many manufacturers are also developing high-power LED packages, using technological advantages to reduce costs. Traditional high-brightness LED, a typical single particle 1W (W) ~ 3W package, gradually changed from aluminum oxide (AI2O3) to aluminum nitride (AIN) substrate, but the package has not been fully systemized, because in There must be a compromise between cost and performance. In terms of the material cost of products, aluminum nitride products are seven to ten times more expensive than aluminum oxide. But because it brings higher thermal efficiency, the substrate can be much smaller, so if its cost per unit is four times higher, the overall material cost may only be two times higher. The use of aluminum nitride is another example of a trade-off between cost and performance. The main manufacturers of high-brightness products, such as Philips, Cree and Osram, have used many aluminum nitrides on high-power LEDs. For mainland Chinese companies, even in the high-brightness field, most of them still use aluminum oxide instead of Aluminum nitride. Yole said that for LED companies in mainland China, the balance between cost and performance will be so considered, mainly because they mainly focus on the domestic market. Intellectual property rights on chip structures are a challenge for these companies. They may use flip chip or vertical LED technology to manufacture high-performance devices, but so far it may be a problem to export these devices from mainland China because they do not have intellectual property rights. All in all, even if the cost per illuminance becomes the main consideration in the LED industry, the methods handled by manufacturers are also different. In addition to the different LED packaging practices, differences in manufacturers can also be observed in the system design. Take LED products that replace light bulbs as an example. From medium-power LEDs to high-power LEDs, different packages are used. 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