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.