As we mentioned in an earlier post about the production of the first 12-inch wafer, we wanted to take a look at the rationale for the move to the larger diameter wafers. And it’s all about affordable real estate. Not land, but the amount of quality space on a sapphire wafer that can be used to produce LEDs.
As LED-based products from tablets and HDTVs to residential light bulbs become more popular, the LED manufacturers that supply LEDs to consumer electronics and general lighting markets need to scale up operations to meet the growing demand for LEDs. That means they need more materials to make LEDs like sapphire substrate. Relying on 2- and 4-inch diameter sapphire substrates won’t produce the volume needed to help the consumer electronics and general lighting industries scale up to production levels needed to satisfy the demand.
The table below is an “order of magnitude” guide to the number of LED chips expected from each wafer size. The numbers are estimated based on typical dimensions for a HB (High Brightness) chip. As wafer size increases, more LED chips can fit along the outer perimeter due to reduced curvature, especially for the larger HB chips. This is called the “edge effect” and provides incrementally more chips than just a raw calculation of geometrical area. For example, a 6” wafer will produce approximately 10X to 12X more chips as compared to a 2” wafer, although the geometrical area increase is 9X.
Wafer Size Surface Area # LED Chips
|Wafer Size||Surface Area||# LED Chips|
|4 inch||4 S||4.5 N ~ 5 N|
|6 inch||9 S||10 N ~ 12 N|
|8 Inch||16 S||20 N ~ 22 N|
|12 Inch||36 S||45 N ~ 50 N|
Caption: Chips per wafer guide for various wafer sizes