Lets compare the CSP LEDs available on the market today, from leading LED manufactures. These are: Nichia, Samsung, Philips Lumileds and Seoul Semiconductor.
If important developments happen in the next months, this article will be updated. LG and Everlight announced CSP LEDs but the required information about them is not available and Samsung will release a new product line later this year.
With the street lighting market being one of the early adopters of CSP LED modules the comparison will be made for 5000K color temperature at a high current of 700mA and CRI 70. For potential office lighting applications the second comparison is at 350mA, CRI 80 and 4000K.
For a meaningful comparison we selected LEDs that function at 350 and 700 mA with a voltage between 2.75 and 3.2 V.
For each category we compare the luminous flux and luminous efficacy at the usual junction "lab temperature" of 25ºC and at a more realistic 100ºC. The comparison data is that from the manufacturers datasheet.
CSP at 700mA, maximum 2.5 Watt, for street or outdoor lighting, 5000K, CRI 70.
At the time of this article the aboove seems to be the top of the performance single chip scale LEDs achieve. At 25ºC Nichia has 20% higher flux (304 lm) and 27% better efficacy (145 lm/W) than the second performer, Seoul WICOP (247lm and 114 lm/w). Luxeon Flip Chip White 10 has similar performance (242 lm/w 115lmw) to Seoul while Samsung lags somewhat behind (210 lm and 95 lm/w).
At 100ºC Nichia is still in the first place but it takes a bigger performance hit due to the increased temperature, of 10% compared with 3% for Seoul and Luxeon. Therefore Nichia delivers 273 lm and 130 lm/w, Seoul 240 lm and 110 lm/w, Luxeon 242 lm and 112 lm/w and Samsung 191 lm and 95 lm/w.
Nichia is the only CSP of the four to have 120 viewing angle which will result in better performance in applications that require such a narrow angle.
CSP at 350mA, maximum 1.5 Watt, for office lighting, 4000K, CRI 80+.
For Nichia and Samsung a different LED was chosen for 350mA while for Seoul and Luxeon it is the same LED as at 700mA. While it is usual to have different LEDs for the two current, 350mA and 700mA, the early stage of the CSP market for lighting can explain while some manufacturers still do not offer such.
At 25ºC Nichia has 12% higher flux (146 lm vs 129 lm) and very slightly better efficacy (139 lm/W vs 139 lm/W) than the second performer, Seoul WICOP . Very close comes the Luxeon Flip Chip White 10 (121 lm/w and 125 lm/w) while Samsung lags somewhat behind (115 lm and 111 lm/w).
At 100ºC Nichia is still in the first place but with a tiny margin, as it takes a bigger performance hit due to the increased temperature, of 10% compared with 3% for Seoul and Luxeon. Therefore Nichia delivers 127 lm, Seoul 125 lm,Luxeon 117 lm and Samsung 104 lm. Except Samung, the luminous efficacy for all ranges between 120 and 128 lm/w, with Seoul on top with 128 lm/w.
After checking the performance of the above CSP several points arise.
Significant progress still is yet to come for CSP.
Luminous efficacy has a lot to go until it can match the 220 lm/w of Mid-Power packaged LEDs.
Luminous flux from a single chip and therefore density is behind that of High Power LEDs, where for example the Cree XPH 35 reaches 1800 lm + and XP-G3 777 lm. About luminous density, the Cree XPH 35 has on average 154 lm per square mm while the top CSP from Nichia only 66 lm.
When it comes to LED arrays or COBs the question is if arrays of CSPs will be easier to integrate into a fixture and be available in as many versions. Today there seems to be an out of the box COB in the 500-20000 lumen range, ready to be assembled even by hand into every kind of down-light or floodlight.
With the current performance picture it seems more realistic to consider that CSP will only find niche markets in the near future. Significant technological progress is needed to replace any of the standard package LEDs, mid power, high power or COB. Progress that will require investment that will come only if the market responds proportionally.
If "slimmer design" and "wider view angle" will be considered as such an important leap forward that will warrant the replacement of packaged LEDs is yet to be seen...