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Size

With the LED market forecasted to experience CAGR of more than 30 percent between 2010 and 2015, LED manufacturers are under increasing pressure to deliver greater and greater quantities of LEDs for use in everything from smart phones, tablets and HDTVs to residential light bulbs, automotive and street lighting.  The next big growth market for LEDs is general lighting.  However, widespread adoption remains tempered by price – a single LED lightbulb can cost $20 to $40. 

 

To address growing demand higher quantities as well as the need for cost reduction, LED manufacturers are migrating to large diameter sapphire wafers.  Simply stated, the larger diameter substrates (six- or eight-inch, as opposed to traditional two-inch wafers) yield many more chips.  For example, 10,000 six-inch wafers can yield the same number of LEDs as 100,000 two-inch wafers.

 

The following chart illustrates the exponential increase in yields by wafer size.

 

Wafer Size

Surface Area

# LEDs possible

2 inch

Y

2,000

4 inch

4y

10,000

6 inch

9y

25,000

8 Inch

16y

40,000

12 Inch

36y

100,000

 

 

The numbers are approximate, as yield is also impacted by LED chip design for the intended application.  Also, as wafer size increases more chips can fit along the outer edge as the curvature is reduced.  This so-called “edge effect” provides incrementally more chips than just a raw calculation of geometrical area.  For example, a six-inch wafer produces approximate 12 times as many chips compared to a two-inch wafer, even though the geometrical area increase is 9X.

 

To capitalize on this trend toward greater manufacturing efficiencies and reduced cost, sapphire makers are pursuing methods of producing high-quality sapphire wafers in larger diameters.  In 2010, the industry’s first 12-inch wafer was produced. 

For a graphic look at large diameter wafers and yield, download Larger Wafer, Larger Yield.