Sunday, June 7, 2009

When will LEDs be truly able to replace Screw in Light bulb?

This was one of the hottest topics some 14 years ago when we met some of senior marketing staff of one European incandescent lamp company saying that the LED screw in light bulbs would be come a commercial product 10 years later, waited until 2004, well, still could not see that to be materialized!

There was great promise and a prominent wish, but the path won’t be easy. Key persons of the major LED players such as Osram, Lumileds and Cree had numerous discussions about this over the years in many consortium and LED shows.

The answer turned out to be less than simple. For one thing, a typical 5mm LED produces about 6 lumens. A commercial lighting fixture would require hundred thousands of such LEDs, bring more technical concerns for driver designers, and in the end consuming more or less the same power as a florescent lighting fixture of the same output.

The pros of for LEDs in lighting fixture comes when you design the LEDs for that purpose, and LED can achieve higher output efficiency, directability of the beam, and reliability that you can’t get any from the best CCFL.
Recently there are a lot of replacement LED light bulb made in large quantity using standard 5mm LED, and sooner we see more and more failed and or burnt out. That was because they are overdriven to the limit that it can designed to withstand, over driven a LED will degrade the epoxy encapsulant. Then the epoxy becoming yellowish, and gradually it starts to crack, once it cracks, the LED will likely to fail.

On the way I returned from Malaysia a couple of days ago, I went to inspect most of the LED lamps that was made with 20 over vertical Lamp in the Airport Express Train at HK Airport.
Obviously that I could see at a low of failed LED in each light fixture. And No one is found to be full lighting up. The train has been running for over ten years and that is the life time for the LED, well I could see that they may not using the bets of his kind and I could remember that the light intensity drops as time goes by!

The lure of the huge compact incandescent-bulb replacement market would seduce the supplying food chain for low cost replacement light bulb using LED by Asian Suppliers, coupled with the entry of low-cost white box producers from China, quickly drove vendors to trade away the long life in exchange for lower cost.

This led to an unfavourable situation in which general consumers often don’t understand the quality of the LED lamp they are buying. In fact in many applications, inexpensive LED light fixture aren’t really direct replacements for ordinary light bulbs or CFL lamp at all.
The consumers buy the wrong bulb for their purpose and get frustrated when it doesn’t work. In China, now we can buy from the market of some bundle of 20 5mm LED light bulb at a price if merely RMB18.00. (USD2.0) This is a incredible low price for the number of LED they have, the chip and associated circuitry. But who know how long these LED can last. Do not forget a typical good quality LED can last 50,000 to 60,000 hours.

All LED designer is doing the best to use different material, manufacturing process to build a LED with good conductive cooling. The incandescent lamps are designed to survive with only radiation cooling. And today, the cost per Lumen of LEDs is still 10X-20X more expensive to replace CFLs and incandescent lamps respectively.

This price different was 20-40X two years ago, the ASP of these good LED is dropping at a mush faster rate that 5 years ago. In order that the LED bulb to be made successful, it has to be reliable, the fixtures must exploit the long life of properly-designed LED lighting to have a competitive position.

On the other hand , the EnergyStar standards will be critical to the development of this market. The beauty of LED lighting is not its cost, or even its efficiency, but the features that it can offer beyond just illumination. Today a typical screw-in light bulb is not expected as cheap as the energy lamp nor the incandescent lamp.

Most of us is using low-cost manufacturing in Asia today. The difference in cost of LED lighting is in the choice of materials and or type of the die bonding process. For instance, you can choose to use inexpensive epoxy that will fail, or you can choose to replace it with a thin film flip chip process which does not contain any epoxy and with excellent gold to gold heat dissipation to keep the LED cool, and there is resistant to light degradation but are more expensive as at price of few times higher.

The substrate, the type of bonding process either epoxy, direct Eutectic, flux eutectic or flip chip, the phosphor that goes over the LED and adds a yellow component to the LED’s blue emission to product white light *1 and the die itself are the key components in a lamp. There are lots of trade secrets and IP in this business, and most of the LED manufacturing or suppliers are quite vertically integrated.
There’s only a core set of companies that have the IP for white LEDs. That could limit competition from low-cost producers copy cats who don’t know how to do it well.
Many consumers have had access to long-life light bulbs, and have steadfastly unwilling to pay a premium for them. Of course there are certain pioneers who has been using LED light bulb at home, hotel as street lamps.

Nowadays there are 70 percent of the lighting-fixture market in the US is commercial, only less then 2% of the user are residential. Incandescent lamp sales are declining as people switch to more energy-efficient lamps such as energy saving lamp as the majority. US and other advance country in Asia are obviously to be lagging in that trend.

If you explore homes in Europe, you will find very small number of incandescent bulbs, and quite common that lamp will be on a dimmer. “In Western countries of Europe, consumers are more eager to pay additional money to enhance a green lifestyle. They are keen on looking for LED light bulbs than any other country in the world.

Friend of mine who is the senior engineer for LED manufacturer asked me what about the maximum light output that we can obtain form the LED. And If that LED lamp can last that long without breakdown as it was listed as one of the sales slogan of 50,000 hours?

In general, higher junction temperature and higher current will mean lower life. There are several failure modes on LEDs, but which one is most likely depends on the architecture of the particular lamp.

“In theory, physics says you could get about 230 Lumens/Watt at perfect efficiency. Most products today are in the neighborhood of 80-90 Lumens/W, and we have cool white lamps [emitting light with a higher color temperature] in the laboratory producing about 130-160 Lumens/W.

Certain users prefer slightly warmer light, and the theoretical perfect efficiency would produce only about 200 Lumens/W at the lower color temperature. The major players had something in the neighborhood of 150 Lumens/W in the lab. But these are hand-built devices. Commercial available device are in the neighbouring of 70-80 lumens/W.

As there is still a need for certain technology breakthrough for higher efficiency say commercial available 200 lumen/W LED. LED should be made at a cost of say 30% of the current LED., Then with these added feature of lumen light intensity per dollar is least 5X better than the current available LED lamp solution.

Then that will be the time for public to accept the LED light bulb to be a standard for domestic application, at that time I think your Incandescent Lamp will be come kind of collectible item and we can only seeing these at Museum!

When that day will be? I think that is 2012.

There are three ways of producing high intensity white-light using LEDs. One way is using RGB LEDs. One is to use individual LEDs that emit three primary colors– red, green, and blue, and then mix all the colors to produce white light. The other is to use a phosphor material to convert monochromatic light from a blue or UV LED to broad-spectrum white light, much in the same way a fluorescent light bulb works.

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