Chip-on-Board LED Arrays

As LED producers continue to move to chip-on-board designs, the size of light-emitting surfaces is shrinking.

Typical "fried egg" appearance of a CoB design, this one from Philips Lumileds.

LEDs Magazine recently ran a survey of the historical movement of LEDs from separate dies to packaged arrays -- so-called chip-on-board (CoB) packages. The article devotes special attention to the evolution of connectors as the industry struggled to adapt to the wide variety of CoB products on the market (now well over 50 of them, according to the magazine).

The move to CoB has been under way for two years or so. What we have seen in recent months is the introduction of CoB designs with smaller light-emitting surfaces (LES). By shrinking the light source, these products are better able to address the directional applications for which the earlier, wide-area emitter CoB designs were not well suited.

Here are a few of the small-LES products that have been introduced recently.

• Cree XLamp CXA1304 and CXA1816: These emitters, announced early in June, have LES diameters of 6 and 12 mm respectively. They have maximum lumen outputs of 1,000 and 3,800 lumens and are available in a full range of color temperatures. CRI of 80+ is standard, but a 95+ option is available across the line. Efficacy is given as 102 lm/W (typical) at 85°C for the CXA1304. Here is a summary from LEDs Magazine.


• Lumileds Luxeon COB: At the end of June Lumileds (sponsor of this site) expanded its COB line with arrays featuring LES sizes of 9, 13, and 15 mm. Output ranges up to 6,000 lumens. Typical CRI is over 80 at 85 °C. Efficacy is given as 120 lm/W at 36 volts and a junction temperature of 85°C. Here is a press release about the introduction.


• Osram Soleriq S 13 and Duris S: The former has an LES diameter of 13.5 mm, maximum output of 1,500 lumens, efficacy of 100 lm/W, and CRI above 80. The latter has the smallest LES of the lot (so far) at 5.8 by 5.2 mm. The link above specifies a typical output of 500 lm at 200 mA, but does not give a maximum.

Much of the innovation in LED engine development is happening in the area of CoB arrays. Efficacies are rising; color binning, already simplified by the use of multiple LEDs, is improving; some suppliers are innovating in substrates. Both more variety and lower prices are likely to result.

Related post:

• Connectors for LED Arrays

— Keith Dawson , Editor-in-Chief, All LED Lighting