Far Red LED PLCC 2835 Specification - Size 2.8x3.5x0.65mm - Forward Voltage 1.8-2.6V - Power 468mW - English Technical Document

1. Product Overview

This specification covers a high-performance Far Red light-emitting diode (LED) in a standard PLCC-2 package (2.8mm x 3.5mm x 0.65mm). The device utilizes AlGaAs (Aluminum Gallium Arsenide) epitaxial layers on a GaAs substrate to achieve efficient emission in the deep red region (730-740 nm). Designed primarily for horticultural lighting, tissue culture, and landscape illumination, this LED combines a wide viewing angle (120 degrees) with robust reliability suitable for automated SMT assembly.

Key features include:

• Package: PLCC-2, 2.8mm x 3.5mm x 0.65mm
• Peak wavelength: 730-740 nm (Far Red)
• Total radiant flux: 40-140 mW at 150 mA
• Forward voltage: 1.8-2.6 V at 150 mA
• Viewing angle: 120 degrees
• Moisture sensitivity level: MSL 3
• RoHS compliant

2. In-Depth Technical Parameter Interpretation

2.1 Electrical and Optical Characteristics (Ts=25°C)

All measurements are performed under a standardized environment with a solder point temperature of 25°C. The LED is tested at a forward current of 150 mA unless otherwise noted.

• Forward Voltage (VF): Ranges from 1.8 V (min) to 2.6 V (max) at 150 mA. Typical value is not explicitly given but lies within the binning range. The measurement tolerance is ±0.1 V.
• Reverse Current (IR): Less than 10 µA at VR = 5 V, indicating excellent junction quality.
• Total Radiant Flux (Φe): 40-140 mW at 150 mA. This is the total optical power output measured by an integrating sphere. Tolerance: ±10%.
• Viewing Angle (2θ1/2): 120 degrees typical (full width at half maximum), providing a wide emission pattern suitable for uniform illumination.
• Peak Wavelength (λp): 730-740 nm, centered in the far-red region critical for plant photomorphogenesis (phytochrome Pfr absorption). Tolerance: ±1 nm.
• Thermal Resistance (RTHJ-S): 35°C/W typical from junction to solder point, essential for thermal management calculations.

2.2 Absolute Maximum Ratings

Exceeding these limits may cause permanent damage. The device should be operated within the specified safe operating area.

• Power Dissipation (PD): 468 mW
• Forward Current (IF): 180 mA (DC)
• Peak Forward Current (IFP): 300 mA (1/10 duty cycle, 0.1 ms pulse width)
• Reverse Voltage (VR): 5 V
• Electrostatic Discharge (ESD HBM): 2000 V
• Operating Temperature (TOPR): -40 to +85°C
• Storage Temperature (TSTG): -40 to +100°C
• Junction Temperature (TJ): 115°C max

Derating: At high ambient temperatures, the forward current must be reduced according to the solder temperature vs. forward current curve (Fig. 1-10) to ensure junction temperature stays below 115°C.

3. Binning System Explanation

The LEDs are sorted into bins for forward voltage, peak wavelength, and total radiant flux at 150 mA. This enables customers to select devices with narrow parametric spreads for consistent system performance.

3.1 Forward Voltage (VF) Bins

Eight bins from B1 to E2 cover the range 1.8-2.6 V in 0.1 V increments:

• B1: 1.8-1.9 V
• B2: 1.9-2.0 V
• C1: 2.0-2.1 V
• C2: 2.1-2.2 V
• D1: 2.2-2.3 V
• D2: 2.3-2.4 V
• E1: 2.4-2.5 V
• E2: 2.5-2.6 V

3.2 Peak Wavelength (λp) Bins

Two bins are defined:

• R25: 730-735 nm
• R26: 735-740 nm

3.3 Total Radiant Flux (Φe) Bins

Two luminous flux bins:

• FR: 40-90 mW
• FR2: 90-140 mW

Note: The combination of VF, wavelength, and flux bins is listed on each reel label for traceability.

4. Performance Curve Analysis

4.1 Forward Voltage vs. Forward Current (Fig. 1-7)

The graph shows a typical exponential I-V characteristic. At 150 mA, VF is around 2.0-2.2 V (mid-range). The curve is steep, emphasizing the need for current-regulated driving to avoid thermal runaway.

4.2 Relative Intensity vs. Forward Current (Fig. 1-8)

The light output increases quasi-linearly with current up to about 120 mA, then slightly saturates at higher currents due to junction heating. At 150 mA, relative intensity is approximately 90% of the value at 120 mA.

4.3 Temperature Dependence (Fig. 1-9, 1-10, 1-11, 1-12)

• Relative Flux vs. Solder Temperature: As temperature rises from 20°C to 100°C, the relative luminous flux decreases by about 30% (typical for AlGaAs LEDs).
• Maximum Forward Current vs. Temperature: To keep TJ ≤ 115°C, the allowable forward current must be reduced above 60°C. For example, at 85°C, IF should not exceed 120 mA.
• Forward Voltage vs. Temperature: VF decreases linearly with temperature (approx. -2 mV/°C), which is typical for LEDs.
• Wavelength vs. Temperature: The peak wavelength shifts slightly to longer wavelengths (red-shift) with increasing temperature, about +0.03 nm/°C.

4.4 Spectrum Distribution (Fig. 1-13)

The emission spectrum is narrow (FWHM approximately 20-25 nm) centered at 730-740 nm. The peak matches the absorption peak of plant phytochrome Pfr (730 nm), making it ideal for photoperiod control in horticulture.

4.5 Radiation Diagram (Fig. 1-14)

The emission pattern is Lambertian-like, with relative intensity dropping to 50% at ±60 degrees off-axis, confirming the 120-degree viewing angle.

5. Mechanical and Packaging Information

5.1 Package Dimensions

The PLCC-2 package has a top-view footprint of 2.80 mm x 3.50 mm, with a height of 0.65 mm. The bottom view shows two anode/cathode pads (A: Anode, C: Cathode) with polarity marking on the top. Tolerances ±0.2 mm unless noted.

5.2 Soldering Pattern

Recommended soldering pads are provided in Fig. 1-5. The pattern includes two rectangular pads with dimensions 1.90 mm x 2.10 mm (anode) and 2.10 mm x 1.90 mm (cathode) to match the bottom terminals.

5.3 Polarity Identification

A clear polarity mark (notch or dot) is present on the top surface. The cathode is typically the larger pad (see Fig. 1-4).

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

The recommended reflow profile (Fig. 3-1) conforms to JEDEC standards. Key parameters:

• Ramp-up rate: 3°C/s max
• Preheat: 150-200°C for 60-120 s
• Time above 217°C (TL): 60 s max
• Peak temperature (TP): 260°C for 10 s max
• Cooling rate: 6°C/s max
• Total time from 25°C to TP: ≤8 minutes

Only two reflow cycles are allowed. Hand soldering: iron temperature <300°C, <3 seconds, one time only.

6.2 Moisture Handling

The LEDs are moisture-sensitive (MSL 3). Before opening aluminum bag: store <30°C / 75% RH, use within 1 year. After opening: <30°C / 60% RH, use within 24 hours. If exceeded, bake at 60±5°C for ≥24 hours before use.

6.3 Cleaning and Handling Precautions

The silicone encapsulant is soft; avoid mechanical pressure on the lens. Use only isopropyl alcohol for cleaning; ultrasonic cleaning is not recommended. Adhesives that outgas organic vapors must be avoided. Anti-static precautions are mandatory (ESD sensitivity 2000 V HBM).

7. Packaging and Ordering Information

7.1 Packaging Specifications

Each reel contains 4000 pieces (max). Carrier tape dimensions are specified in Fig. 2-1, with a feed direction indicator and polarity marking. Reel dimensions: 178 mm diameter (with 13.5 mm hub), 10.5 mm width. Anti-static bag and cardboard box packaging (Fig. 2-2 to 2-5).

7.2 Label Information

Each reel is labeled with Part Number, Spec Number, Lot Number, Bin Code (including VF bin, wavelength bin, flux bin), Quantity, and Date code.

Part number example: RF-AL-T28352H0FR-00 (encoding package, color, and flux/wavelength bin).

8. Application Suggestions

This Far Red LED is ideally suited for:

• Plant Factories: Supplemental lighting in vertical farms to promote flowering and fruiting (phytochrome interaction).
• Tissue Culture: Monochromatic light sources for in-vitro propagation without heat damage.
• Landscape Lighting: Accent lighting with deep red hue for gardens or architectural features.
• General Illumination: Used in combination with blue/deep red LEDs to create broad-spectrum horticultural fixtures.

Design considerations:

• Always use a current-limiting resistor or constant-current driver to prevent overcurrent.
• Ensure adequate heat sinking on the solder pads to keep junction temperature below 115°C.
• For arrays, consider voltage drop across long traces and current sharing mismatches due to VF bin spread.
• Avoid exposing the silicone lens to high sulfur, chlorine, or bromine concentrations (limits: S <100 ppm, single Br/Cl <900 ppm, total Br+Cl <1500 ppm).

9. Technical Comparison with Competing Technologies

Compared to standard red AlGaInP LEDs (630-660 nm), the AlGaAs Far Red LED offers higher radiant efficiency in the 730-740 nm band. This wavelength is specifically required for phytochrome Pfr response, which is not achievable with standard red LEDs. AlGaAs also demonstrates better temperature stability than AlGaInP in the far-red region, though thermal management remains critical.

10. Frequently Asked Questions

1. Can I drive this LED at 200 mA? The absolute maximum is 180 mA continuous. Driving at 200 mA may exceed the junction temperature rating if thermal resistance is not accounted for. Not recommended.
2. What is the typical efficiency (mW/mA)? At 150 mA, radiant flux is ~90 mW (typical mid-bin), giving ~0.6 mW/mA. Efficiency decreases with current due to droop.
3. How do I select the correct bin for my design? For precise wavelength, choose R25 or R26. For consistent brightness, select FR or FR2. For voltage matching in series strings, pick a narrow VF bin.
4. Is this LED compatible with common SMT pick-and-place equipment? Yes, the PLCC-2 package is standard and can be handled by most machines with appropriate nozzle (avoiding pressure on the silicone lens).

11. Practical Application Case Study

Case: Indoor Lettuce Production
A plant factory using 20% blue (450 nm) and 80% far-red (730 nm) LEDs at a total PPFD of 200 µmol/m²/s increased lettuce yield by 15% compared to a 70% red (660 nm) + 30% blue spectrum. The far-red component promoted leaf expansion and accelerated the growth cycle. The LEDs were driven at 120 mA (to stay within thermal limits) and mounted on aluminum-core PCBs with thermal vias. No failures were observed after 10,000 hours.

12. Operating Principle

The LED is based on a double-heterostructure (DH) AlGaAs p-n junction grown on a GaAs substrate. When forward biased, electrons and holes recombine radiatively in the active region, emitting photons with energy corresponding to the bandgap of AlGaAs (~1.7 eV, giving ~730 nm). The PLCC package provides a reflective cavity to extract light from the top, while the silicone lens protects the chip and enhances light extraction. The wide bandgap of the cladding layers confines carriers efficiently, yielding high internal quantum efficiency.

13. Technology Trends and Outlook

The demand for Far Red LEDs is growing rapidly with the expansion of controlled-environment agriculture. Innovations focus on improving wall-plug efficiency (currently ~25-35%) and reducing thermal resistance through advanced packaging (e.g., ceramic substrates, flip-chip). Future trends include integration with sensors for closed-loop spectrum control and multi-junction structures that combine blue and far-red emitters in a single package. The AlGaAs material system remains dominant for deep reds, with further improvements in droop behavior expected.