TSMC and Seoul address LED issues at SIL Europe

Nov. 19, 2013
During the Strategies in Light Europe Investor Forum, TSMC discussed its phosphor-on-die approach to LEDs while Seoul Semiconductor discussed the market opportunity and homogenous substrate development.

The Strategies in Light (SIL) Europe conference kicked off with an Investor Forum and a series of workshops; in the former, LED makers TSMC and Seoul Semiconductor addressed the component sector. TSMC focused on its strategic approach to solid-state lighting (SSL) based on its Phosphor-on-Die (PoD) LED technology. Seoul Semiconductor commented on its progress in gallium-nitride-on-gallium-nitride (GaN-on-GaN) LED technology and on the state of the market.

Jacob Tarn, CEO of TSMC Solid State Lighting Ltd, started his presentation by examining the cost structure of an LED-based A19 lamp, saying that LEDs make up 40% of the bill of materials (BOM). The more acute problem, according to Tarn, is that the packaging of the LED chip incurs a disproportionately large share of the LED component cost. That realization led TSMC to the PoD concept where phosphor is applied directly to the die at the wafer scale, and the LED manufacturing process is simplified with the flip-chip design able to be soldered directly to a substrate such as a metal-core printed circuit board (MCPCB).

TSMC Phosphor-on-Die (PoD) LEDs

Tarn said that PoD technology has yielded low thermal resistance, elimination of wire bonds, and a compact footprint among other advantages. The company is offering the die in 1×1- and 1.4×1.4-mm form factors. More sophisticated customers can buy the die, and TSMC will offer the LEDs on small MCPCB modules and in larger modules with driver electronics and in the future intelligence and controls.

PoD enables new approaches

The bare die offer some interesting design possibilities. Tarn said that the die can be closely packed in arrays — virtually a multi-emitter packaged LED — mounted on a substrate such as an MCPCB. Tarn also said that SSL developers will be able to develop a single optics package that can deliver different beam patterns based on the positioning of the PoD LEDs on a substrate.

Alas, TSMC has not made a significant impact on the LED component space to date despite investing substantial money. Tarn said the R&D investment in epitaxial technology totaled $1.6 billion, covering both the LED and high-power semiconductor space. The company has studied GaN-on-silicon (GaN-on-Si), GaN-on-GaN, and GaN-on-sapphire architectures, but for now is manufacturing products based on sapphire just as most of the industry is. Tarn said that the company is shipping 10–15 million LEDs per month.

Where TSMC could have a bigger impact is in the GaN-on-Si area should the company develop a process that is competitive from an efficacy and lumen output perspective with sapphire approaches. The parent company is the largest contract fabricator of digital ICs, and has plenty of depreciated, automated silicon fabs that could handle the back-end silicon-based LED manufacturing process.

Tarn also provided a glimpse of what is coming from TSMC, showing a slide on tunable lighting products based on the PoD technology. When questioned on the topic, he said that TSMC has a new approach to tunability along with a strategic partner, and that the platform would formally launch at Light+Building next year.

Seoul Semiconductor presentation

William Shin, executive vice president of marketing at Seoul Semiconductor, meanwhile, spent significant time in his presentation discussing the companies AC-LED technology. We won't cover that technology here since we have written a number of article on the topic of late. But Shin did address market and substrate issues as well.

Shin said that today LEDs have penetrated only 4% of the lighting market. That figure seems incredibly low when you consider projects such as in Los Angeles where the city has installed 140,000 LED streetlights. But the point is that SSL is still a very young industry. That fact is leading Seoul to invest 15% of sales in R&D, both in new more-efficient substrates and in its AC-technology segment.

Seoul made a major announcement of its GaN-on-GaN nPola (non-polar) LED manufacturing platform in mid-2012, asserting that the resulting LEDs would be five times improved in terms of lumen density. Soraa has made similar claims for its GaN-on-GaN LEDs.

When pressed about the commercial status of the GaN-on-GaN technology, Shin said, "We have just started to commercialize it. We have launched a product in Japan first." But Shin acknowledged that the nPola products had yet to have an impact on Seoul sales at this time.