Infrared SMD LED Datasheets

Choosing Between 850 nm and 940 nm SMD Infrared Emitters

The two workhorse wavelengths in surface-mount infrared are not interchangeable, and picking the wrong one shows up as either a faint red glow on camera or a sensor starved for signal. Silicon photodetectors peak near 850 nm, so an 850 nm emitter delivers roughly 30–40% more usable detector current than an equivalent 940 nm part. The trade-off: 850 nm dies leak a small visible-red component during operation, while 940 nm is essentially invisible to the human eye.

Package Footprints and Beam Geometry

SMD IR emitters follow the same metric footprints as visible SMD LEDs — 0603 (1608), 0805 (2012), and 1206 (3216) — so existing placement footprints and pick-and-nozzle programs carry over. Beam geometry is set by the molding lens integrated into the package: narrow ~30° parts concentrate radiant intensity for distance sensing and beam-break counters, while wide 100–140° parts build uniform flood arrays for room-scale presence detection. In dense arrays, overlap the 50% intensity contours at the working distance to avoid sensitivity dead zones.

Drive and Pulsing Practice

• Sensing circuits should pulse at 1:10 to 1:100 duty cycle — peak current can then run 2–5× the DC rating without thermal penalty
• Synchronous detection (pulsing the emitter and gating the receiver together) rejects ambient light and is standard in reflective sensing
• Camera illumination runs DC or low-frequency PWM above the frame rate; verify the camera’s IR-cut filter is removed or bypassed for the illuminator band
• Match the emitter wavelength to the photodiode’s response curve, not just its peak — see our infrared camera application case study for a worked design

Frequently Asked Questions

Why does my 850 nm array show up on smartphone video?

Phone cameras without IR-cut filters resolve the weak visible tail of an 850 nm die. If the installation is photographed or recorded, specify 940 nm and budget for the output reduction by adding emitters or narrowing the beam.

What radiant intensity do I need for a beam-break sensor at 2 meters?

Work backward from the receiver’s minimum irradiance: for a typical phototransistor needing 0.1 mW/cm², a 30 mW/sr narrow-angle emitter aimed directly at the receiver covers 2 m with margin. Wider angles require proportionally more die or closer spacing.

Are SMD IR parts as reliable as DIP for outdoor exposure?

Yes, when the board is conformally coated. SMD packages carry the same moisture-sensitivity handling rules — bake per MSL rating before reflow and avoid reworking a populated IR array with a hot air gun, which delaminates the lens.