Toshiba Unveils 'Industry's Smallest' White LED Chip

Mar 26, 2014
Jyunichi Oshita, Nikkei Technology Online
The "CSP-LED" emitting light. The white-light model (color temperature: 5,000k, left) and the incandescent-color model (color temperature: 2,700k).
The "CSP-LED" emitting light. The white-light model (color temperature: 5,000k, left) and the incandescent-color model (color temperature: 2,700k).
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It measures 0.65 x 0.65mm.
It measures 0.65 x 0.65mm.
[ If it clicks, the expanded picture will open ]

Toshiba Corp developed what it claims is the industry's smallest (0.65 x 0.65mm) white LED for lighting applications.

With the company's wafer-level CSP (chip scale package) technology, the footprint of the LED, "CSP-LED," is 50% or more smaller than those of its competitors' LEDs. Because the new LED allows to drastically reduce the size of light source, it enables to design lighting equipment more freely as well as to make use of space in which a conventional light source cannot be installed.

Toshiba will start shipping samples of the LED in late April 2014.

Toshiba has been mass-producing white LEDs using GaN-on-Si technology, which forms a gallium nitride (GaN) layer on a 200mm-diameter silicon (Si) wafer. They can be manufactured at low costs, compared with white LEDs using a sapphire wafer. Currently, the company is producing the white LEDs at a rate of 50 million to 100 million units per month.

Using core technologies of semiconductor unit

This time, Toshiba applied core technologies of its semiconductor unit such as packaging and Cu multi-layer wiring technologies to white LEDs, it said. Specifically, the company used its wafer-level CSP technology, which is used for installing RF devices, etc.

The technology forms wiring and pins and conducts resin sealing at the wafer level, and, then, the wafer is separated into chips. To apply this method to white LED, Toshiba newly developed a device structure that enables to directly pull out copper (Cu) electrodes from the reverse side of the light-emitting layer without using wire bonding.

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The overview of the wafer-level CSP process is as follows. First, Cu electrodes are formed by plating on a 200mm wafer equipped with white LEDs, and, then, it is sealed with resin. The wafer is turned over, and the Si substrate is removed. Lastly, a fluorescent material layer is formed on the entire surface of the wafer, and the wafer is separated into chips.

"We used our own knowhow such as the conditions for the formation of the fluorescent material layer in each process," Toshiba said.

According to Toshiba, the sizes of conventional white LEDs for lighting applications are 1 x 1mm or larger. Compared with them, the company reduced footprint by 50% or more this time. In comparison with Toshiba's existing products, footprint was reduced by about 90%. As a result, it became possible to mount LEDs on thin, linear substrates and other substrates having shapes and sizes that make it difficult to mount conventional LEDs.

Toshiba will apply the new technology to its products whose wattage is 0.2-0.6W. It will start to ship samples of the white-light model (color temperature: 5,000k) and the incandescent-color model (color temperature: 2,700k) in late April 2014 and samples of other models in May 2014. The prices of the samples are about ¥20 (approx US$0.2).

Toshiba plans to define the products using the wafer-level CSP technology as the core products in its line of white LEDs and apply the technology to 1W-class products. The company will exhibit the new LED at "light + building," a trade show on lighting technologies, which will take place from March 30, 2014, in Frankfurt, Germany.