NIR LED Illumination for AOI and Electronics Inspection
TeraPower LED is the authorized United States distributor of REVOX, Inc., a Japanese manufacturer of high-power industrial LED components. This page explains how near-infrared (NIR) illumination is used in automated optical inspection (AOI) and electronics inspection, how to choose a wavelength, and which NIR COB LED emitters we supply for building that illumination.
We supply bare COB LED emitters (components) for machine builders, system integrators, and research groups that design their own illumination heads. If you would rather buy a finished light source than build one, REVOX also makes complete illumination systems - see fiber optic illuminators and LED line lights, both quoted on request.
Why near-infrared shows what visible light cannot
NIR imaging relies on two effects working together. Longer wavelengths transmit through many materials that block visible light, and specific materials absorb specific NIR bands. REVOX describes this combination as the reason NIR imaging makes internal structure visible: the light passes through the surrounding material, while absorbing regions stay dark to the camera.
Two inspection cases published by REVOX are directly relevant to electronics manufacturing:
- Circuit board trace patterns. REVOX reports that NIR wavelengths sharpen the line pattern of a circuit board. Inspection under visible white light is possible, but the sharper NIR image allows finer inspection. The published setup uses a 940 nm fiber light source with a broadband NIR camera.
- Silicon wafer transmission inspection. REVOX reports that NIR wavelengths pass through a silicon wafer, so the wafer can be inspected in transmission, using an 1100 nm source. REVOX also states that its NIR LED light sources deliver more optical power than a 150 W NIR halogen lamp while suppressing heat generation.
The same two effects are used outside electronics, for example to inspect foreign objects inside colored liquids, or the contents of plastic cases that are opaque in the visible range.
Match the wavelength to your camera first
In NIR inspection the practical constraint is the sensor, not the light source. Silicon sensors are limited by the 1.12 eV bandgap of silicon, which places the response cutoff near 1100 nm, with quantum efficiency already falling steeply before that point. InGaAs sensors cover roughly 900–1700 nm instead.
| Wavelength | Typical camera | Typical use in electronics inspection |
|---|---|---|
| 740 nm | Standard silicon CMOS or CCD | Added contrast on boards, films, and assemblies without changing to an infrared camera |
| 1060–1150 nm | InGaAs (silicon response is marginal at best) | Transmission through materials that block visible light, including silicon wafer inspection |
| 1200–1300 nm | InGaAs | Deeper transmission where the shorter bands are still absorbed |
This is why 740 nm is the usual entry point for AOI: it adds NIR contrast while keeping the existing silicon camera. If the task depends on transmission through silicon, the wavelength has to sit beyond the silicon cutoff, and an InGaAs camera becomes part of the specification rather than an option.
Specify radiant flux, not lumens
NIR output is invisible, so photometric units such as lumens or lux do not describe it. Our emitters are rated in watts of radiant flux at a defined forward current, measured with a spectrometer at Tc = 25 °C.
Available flux also drops as wavelength increases, from 15.09 W at 740 nm to 3.64 W at 1300 nm. A system that works at 740 nm will not automatically work at 1300 nm with the same exposure, working distance, and optics, so budget irradiance for the wavelength you actually need.
Check the spectral half-width before specifying filters
Spectral half-width ranges from 36 nm at 740 nm to 78 nm at 1300 nm. If the inspection uses a bandpass filter to reject ambient light, or depends on narrow spectral contrast, the wider bands at longer wavelengths may require the filter to be re-specified.
Plan the thermal path
These are high-power components: 16 chips on a 28.0 × 26.8 mm package, rated for 16 A forward current. Thermal resistance is 0.3 °C/W for the 1060–1150 nm devices, 0.8 °C/W at 740 nm, and 1.0 °C/W at 1200–1300 nm, and junction temperature is limited to 125 °C. Every device includes a built-in 10 kΩ NTC thermistor, so junction temperature can be monitored in the finished assembly rather than estimated.
NIR COB LED emitters for AOI illumination
| Peak wavelength | Model number | Radiant flux (Typ.) | Spectral half-width | Typical camera |
|---|---|---|---|---|
| 740 nm | 740L-120D-16C-2827COB-01 | 15.09 W @ 16 A | 36 nm | Silicon |
| 1060 nm | 1060L-120D-16C-2827COB-01 | 11.7 W @ 16 A | 72 nm | InGaAs |
| 1100 nm | 1100L-120D-16C-2827COB-01 | 9.16 W @ 16 A | 60 nm | InGaAs |
| 1150 nm | 1150L-120D-16C-2827COB-01 | 6.9 W @ 16 A | 57 nm | InGaAs |
| 1200 nm | 1200L-120D-16C-2827COB-01 | 4.0 W @ 16 A | 65 nm | InGaAs |
| 1300 nm | 1300L-120D-16C-2827COB-01 | 3.64 W @ 16 A | 78 nm | InGaAs |
Full specifications, characteristic curves, and outline drawings are on each product page. See NIR COB LED emitters for the complete band, machine vision LED emitters for the UV-to-SWIR range used in inspection, and SWIR COB LED emitters for 1450–1650 nm.
Finished NIR light sources. If your station needs a complete illuminator rather than a bare emitter, REVOX builds near-infrared fiber optic light sources as well. The SLG-150V-NIR is the NIR model in that series, specified by REVOX for external and internal inspection, with closed-loop light output feedback and 10-bit dimming; see fiber optic illuminators for the full lineup. For line-scan inspection, the SPX-TA200 LED line light is available with NIR LEDs. Both are quoted individually.
Wavelengths that are not in the catalog
REVOX assembles its COB and SMD packages in-house in Japan, with die bonding, wire bonding and phosphor coating all performed on its own equipment. Owning the die bonding process is what allows the arrays to be packed this tightly: chips are placed with a chip-to-chip gap of 60 µm, which keeps the emitting area compact enough to couple efficiently into lenses and fiber optics. Because the whole assembly line is in-house, wavelengths outside this catalog can be produced to order. Chip count, array layout, substrate, and package dimensions are configurable as well. If your inspection recipe is built around a wavelength we do not offer as a standard COB product, send us the target wavelength, the optical power you need, and the annual quantity, and we will quote the device.
Standard products cover 365 to 1,650 nm. Wavelengths outside that range, and other chip counts, array layouts or package sizes, are made to order. Tell us the wavelength and quantity you need and we will confirm feasibility with REVOX.
Ordering and sourcing information
Minimum order quantity. Production starts at a single unit. There is no minimum order quantity, so an evaluation build and a production run are both quotable.
Lead time. Approximately one month when parts are in stock at the factory, and 1.5 to 2.5 months when they are not.
Shipping. Orders are shipped either direct from REVOX in Kanagawa, Japan, or through our Torrance, California office. We do not hold U.S. inventory; devices are built to order, which is what drives the lead time above.
Technical support. Technical questions are handled from the United States in English, and we connect you directly with the design team in Japan when a question needs the manufacturer.
Pricing. All products are quoted individually, because pricing depends on wavelength, optical power, chip configuration, and quantity. Use the Request a Quote form on any product page, submit the Custom Order Form for non-standard requirements, or email sales@terapowerled.com.
For more on our distributor status and frequently asked questions, see Authorized U.S. Distributor of REVOX.