IDEC Corp developed a new manufacturing method for pseudo white LED modules made by combining blue LED elements and yellow fluorescent materials.
The new method enables to stabilize product quality and simplify manufacturing process. With the method, an LED device can be packaged just by covering it with a gel-like silicon resin sheet containing a fluorescent material and heating it. Compared with a conventional method that packages an LED device by inpouring liquid resin, the new method can reduce the time used for packaging process to 1/9, IDEC said.
With the conventional method, a "dam" is formed around an LED device on the substrate to keep the resin. Then, the resin and a fluorescent material are churned and poured onto the substrate. Lastly, it is solidified by heat.
However, when the resin and fluorescent material are not equally mixed, the fluorescent material deposits in the resin or the amount of the resin is too large or too small, variations occur, making it difficult to stabilize product quality. When there is a variation in product quality in the packaging process, there are variations in chromaticity, etc
With the new method, when an LED device is covered with the gel-like silicon resin sheet and heated to a temperature of about 150°C, the sheet hardens in about 40 minutes, completing the packaging process. With the conventional method, the whole packaging process (from the formation of the dam to the thermal hardening) takes six hours.
The new method does not cause the deposition of fluorescent material because the gel-like sheet is used, drastically reducing the number of factors that cause a variation in product quality in the packaging process. Moreover, it is expected to drastically simplify production equipment.
The gel-like resin sheet was developed by Nitto Denko Corp and is sold for a wide variety of purposes. IDEC has established new manufacturing methods and prototyped white LED modules by using the sheet. IDEC, which consolidated its production bases for white LED modules for lighting devices in its Hamamatsu Plant, plans to apply the new manufacturing method to all of its modules within fiscal 2013.