LED-backlit LCD TV (LED TV) shipments have seen a ten-fold increase in 2010, and growth is estimated at 2.4 times in 2011. Massive demand has driven down LED costs, and as LED luminous efficacy is expected to reach 150 lm/W in 2012, a further slide in cost is widely anticipated. Meanwhile, as the problem of heat dissipation will soon be effectively resolved, reliability and product life of LEDs will also increase as a result.
While LED technology is maturing, its application market will also expand gradually with the LED lighting segment getting most attention. As global warming has become the hottest issue and energy conservation an irreversible trend nowadays, adoption of high-efficiency lighting equipment will help save massive amounts of energy since lighting accounts for 19% of all electricity consumption. Meanwhile, major countries' decision to phase out incandescent bulbs will also trigger a replacement cycle for bulbs.
LED lighting prices are still much higher than those of conventional lighting now, but according to estimates by Japanese experts, LED lights will become more economical than incandescent bulbs in 19 months (electricity fees included). A further slide in prices will bring more advantages to LEDs on its way to replace traditional lighting.
Besides an upgrade in technology, another crucial link necessary for LEDs' application in the lighting market is standards. This is why the DTF's Taiwan LED Supply Chain Technology Forum 2010 invited Jay-san Chen, director general of the Ministry of Economic Affairs' (MOEA) Bureau of Standards, Metrology and Inspection, as the opening speaker addressing the progress of Taiwan government's promotion of LED standards. Taiwan Lighting Fixture Export Association Chairman David Chang also made a speech in the forum, offering insight into the competition and cooperation between the island's conventional lighting sector and LED industry from a lighting vendor's point of view.
On the technical front, heat dissipation remains the biggest bottleneck for LED packaging. Therefore, VisEra Technologies Company, Polytronics Technology Corporation and TeamChem Company were invited to present their optimized heat dissipation solutions in the forum. Meanwhile, TM Technology and Chroma ATE Inc shared their expertise on power module and testing, respectively, with forum participants, while Epistar Corporation, Taiwan's leading LED chip manufacturer, explored the commercialization of LED lighting and presented its state-of-the-art solutions.
Taiwan steps up pace to establish LED lighting standards
Taiwan's LED industry has become the world's number-one in terms of output, and its output value also ranks second around the world. Due to a lack of common standards, however, lighting vendors still have no basis to rely on when developing products, so the government is accelerating the pace to decide on a set of standards. The standard CNS 15233, made public by the MOEA in December 2008, became the world's first set of standards for street lamps, and the AC LED national standards is also expected to become the first of its kind around the world this year. With cooperation and promotion among the industry, the government and the academic community, it will not be long before LED lighting grows into a full-fledged market.
Among all its number-on titles for different industries, Taiwan was dubbed "the kingdom of lighting" 30 years ago. An integrated supply chain composed of both upstream and downstream vendors was the main reason for the fast development of the island's lighting industry back then. As Taiwan's LED industry is also equipped with an integrated supply chain now, lighting vendors are looking forward to another round of boom for the industry.
However, lighting and photonics are two totally different industries where scores of cultural differences exist. For example, lighting companies are mostly family businesses supported by apprenticeship or father-to-son succession that is rare in the photonics industry. Therefore, there is still a long way to go for the two industries to achieve further integration.
Moreover, LED applications in lighting still need to conquer the problem of conflicting characteristics. For example, the characteristics of LEDs include lower beam and higher luminance of point sources, lack of unified standards, fast development of products, premature performance and higher costs. However, lighting requires comfort, reliability and standardization, with higher demand for illuminance and uniformity but lower lost.
Progress in LED TCB technology
LEDs face serious heat dissipation problem whether they are used in display backlighting or general lighting. Demand for high-power LEDs is rising, and high-power LEDs mean that more heat will be generated.
As traditional heat dissipation tools such as fans or heat sinks are not suitable for backlighting or lighting, the development of LED thermal conductive board (TCB) technology has become an important issue.
Generally speaking, ceramic substrates are the most common TCB and work well with low-power LED. Due to poor thermal conductivity, however, such substrates will suffer serious heat dissipation problems and need to be improved or simply replaced by materials with better thermal conductivity.
For example, Polytronics Technology uses MCPCB substrates as its mainstream technology for applications in edge-lit LED TVs. Such Substrates are manufactured with a dry process for lesser solvent consumption, and its high thermal conductive film is made with a roll-to-roll process.
TeamChem said the technological focus has been mostly on heat conductivity solutions instead of heat dissipation, which is actually the key issue. The surface of substrates is actually uneven in the microcosmic sense and needs to be filled by fluid. It may be a problem to achieve an even surface on the TCB using the traditional MCPCB technology. But it can be solved by using FPCB, a new type of flex board with great thermal conductivity.
VisEra analyzed that silicon will be a better choice in terms of thermal conductivity and thermal diffusion, as aluminum substrates often suffer warpages. In addition, the thermal impedance of silicon substrates can be as low as 5 degrees Celsius/W while that of aluminum oxide is 10-15 degrees Celsius/W. As its thermal impedance is 4 degrees Celsius/W lower than ceramic on average, silicon will have an additional 4,000 hours of life in comparison.
DTF Taiwan LED Supply Chain Technology Forum
Photo: Digitimes, October 2010
