Yiguang Technology

Recently, the prices of mainstream 0.5W and 1W LEDs have dropped rapidly, with a decrease of 5-10% in the fourth quarter of 2011 and a decrease of nearly 40-50% for the whole year of 2011. It is expected that this speed will slow down slightly in 2012, as high-power LEDs still have certain technological barriers and costs, so it is estimated that their prices will decrease by 20-30% throughout the year.

In order to further reduce the cost of LEDs, some suppliers in the industry are currently trying to use cheaper silicon and metal materials as substrate materials to develop high-power LEDs. However, this approach was still a good problem in early 2011, but by the third and fourth quarters of last year, with the demand for LED production capacity and the expansion of sapphire substrate manufacturing capacity, the price of sapphire at the end of last year had decreased by more than half compared to the beginning of last year. For example, at the beginning of last year, the price of sapphire was still over $30, but by the end of last year, the lowest quote was only about $7. When the price of sapphire drops below $10, the advantage of using other materials as substrates becomes less apparent.

The technology of silicon substrate has actually developed quite early, but it has not been developed yet, mainly due to the following important issues: firstly, silicon has many defects and its luminous efficiency is relatively poor. Secondly, when using silicon for epitaxial growth, due to the fact that silicon itself absorbs light, it is necessary to remove the silicon and use other substrates (whether metal or other substrates) as the carrier of the light source. A substrate conversion must be done here, and this process itself is not that easy. Moreover, when you add a process to replace the silicon substrate with another substrate, the benefits of using silicon basically disappear. Using sapphire as a substrate does not require changing the substrate, and the manufacturing process is simple. As the cost of sapphire continues to decrease, the low-cost advantage of silicon will become less apparent.

From the perspective of LED cost, the cost of using silicon carbide as a substrate is much higher than that of sapphire substrate, but the light efficiency and epitaxial growth quality of silicon carbide substrate are better. Silicon carbide materials are divided into two types: opaque and transparent. If transparent silicon carbide materials are used as substrates, the cost is higher. Like silicon materials, opaque silicon carbide also requires substrate conversion after epitaxial growth, which involves another process and has certain yield issues. So currently, we mainly use sapphire material, which has been developed for a long time and is very mature.

As for when LED bulb lights can truly increase in volume, next year should be a particularly special time. Many predictions indicate a significant increase in LED lighting in 2013 or 2014, but some say it will have to wait until 2015. However, based on our recent observations, due to the instability of supply and demand, the decline in backlight demand, and the instability of the European and American markets, the price reduction rate of LED is relatively fast. It is expected that these factors will stimulate the early growth of the LED lighting market. The price of the first energy-saving light bulb was around 20-30 US dollars back then, but now it has dropped to 2-3 US dollars. The current LED lighting bulbs may also follow a similar path, as the price of energy-saving LED bulbs has dropped from around $50 to less than $20. I expect to see the rise of the LED lighting market in the third or fourth quarter of 2012, at the latest by early 2013.

Nowadays, many manufacturers of energy-saving lamps are producing LED lighting fixtures, but we need to see that the price of LED lighting fixtures has dropped from $30 to $10, and many costs have to be compressed. Therefore, what we are concerned about now is "how many lumens can be obtained per dollar". In terms of 800 lumens of light bulbs, the average cost after packaging was approximately $1200 in 2011 (the industry average is around 160-180 lumens), with the best achieving 250 lumens. In early 2012, we planned to achieve 300 or 400 lumens, and the price of LED bulbs will also decrease accordingly.

High voltage LED is our latest attempt to help the industry solve the problems of heat dissipation and light efficiency. Currently, we mainly develop two types of high-voltage 1W LED, around 50V and 70V, for the lighting market. This allows customers to easily meet the requirements of 220V or 110V mains power through different arrangement combinations. We have set up LEDs with these two voltage ranges based on the opinions of circuit control design experts and chip design experts, making them the easiest to match with the mains. This is currently our main recommendation and also the first one we proposed, and many manufacturers are following suit.

The advantage of using high-voltage LEDs is that it reduces the loss of voltage drop and effectively lowers the driving current, allowing for the use of finer copper wires in the circuit. Our high-voltage LED has been in mass production for over a year now. The light efficiency of high-voltage LED is much better, with a single brightness of up to 120lm/W, while low-voltage LED is generally around 100lm/W. Customers can flexibly choose based on luminous efficiency or total output lumens. We design the platform using a 1W LED. Compared with low-voltage LEDs, the thermal energy of high-voltage LEDs will be evenly distributed on the chip, while the thermal energy of low-voltage LEDs will accumulate in a certain area. Although the heat dissipation is done well, it will still crack due to continuous strong heating in this area. High voltage LEDs can uniformly transfer heat energy through the entire chip, so their stability is relatively good.

High voltage LED will be a mainstream demand trend for space limited applications in the future, such as bulb lights and projection lights. In traditional places where high power is used, such as dance table lamps and wall washers, because their space is not limited, some voltage control circuits can be deployed. In this case, high voltage or low voltage LEDs are used, and the difference is not significant. But in small spaces like bubble lamps where it is difficult to arrange control circuits, high-voltage LED chips are a good solution.

At present, the cost of high-voltage LED is higher than that of low-voltage LED, but with the increasing use and production scale of high-voltage LED products, the situation may not be entirely the same. From my current perspective, the process of high-voltage LED is a bit more complex, but after six months or a year, when it becomes a stable market, the yield will increase and the cost will gradually decrease. It is expected that this market will become increasingly stable after the second and third quarters of 2012.

At present, Cree and Osram are also working on high-voltage LEDs, and there are also 2 to 3 companies in China doing so. We currently have some cases of bulb lights using high-voltage LEDs, and finished products have already been sold in the market. Some internationally renowned light bulb manufacturers are using our products.

We are currently involved in many markets. In the past few years, monitor backlighting dominated, but recently we have been paying more attention to the lighting market because it is a new application and an area worthy of everyone's expectations. From the perspective of replacement volume and acceptance, the main market is bulb lights and light tubes, one concentrated in very small light bulbs, and the other dispersed throughout the entire light tube. These two applications and designs are quite different, but they complement each other. (Editor: LEDxume）