SMD LED 18-225/S2G6C-A01/3T Specification - Size 1.6x0.8x0.5mm - Voltage 1.75-2.35V - Power 60mW - Orange/Yellow-Green - English Technical Document

1. Product Overview

The 18-225/S2G6C-A01/3T is a compact, surface-mount LED designed for high-density applications. It is a mono-color device available in two distinct chip variants: the S2 (Brilliant Orange) and the G6 (Brilliant Yellow Green). The primary advantage of this component is its miniature footprint, measuring 1.6mm x 0.8mm x 0.5mm, which enables significant space savings on PCBs, reduces storage requirements, and allows for the design of smaller end-user equipment. Its lightweight construction further makes it ideal for portable and miniature electronic devices.

The LED is packaged on 8mm tape wound onto a 7-inch diameter reel, making it fully compatible with standard automated pick-and-place assembly equipment. It is designed for use with infrared (IR) and vapor phase reflow soldering processes. The product is compliant with key environmental and safety standards, being Pb-free, RoHS compliant, EU REACH compliant, and halogen-free (with Bromine <900 ppm, Chlorine <900 ppm, and Br+Cl < 1500 ppm).

1.1 Target Applications

This LED series is versatile and finds use in various illumination and indication roles. Key application areas include backlighting for instrument panels, switches, and symbols; indicator and backlighting functions in telecommunication devices such as telephones and fax machines; flat backlighting for LCD displays; and general-purpose indicator applications where reliable, compact lighting is required.

2. Technical Parameter Deep-Dive

2.1 Absolute Maximum Ratings

Operating the device beyond these limits may cause permanent damage. The absolute maximum ratings are specified at an ambient temperature (Ta) of 25°C.

• Reverse Voltage (V_R): 5V
• Continuous Forward Current (I_F): 25 mA for both S2 and G6 variants.
• Peak Forward Current (I_FP): 60 mA (at a duty cycle of 1/10 and 1 kHz frequency) for both variants.
• Power Dissipation (P_d): 60 mW for both variants.
• Electrostatic Discharge (ESD) Human Body Model (HBM): 2000V.
• Operating Temperature Range (T_opr): -40°C to +85°C.
• Storage Temperature Range (T_stg): -40°C to +90°C.
• Soldering Temperature (T_sol): For reflow soldering, a peak temperature of 260°C for 10 seconds is specified. For hand soldering, 350°C for 3 seconds is the limit.

2.2 Electro-Optical Characteristics

The following parameters are measured at Ta=25°C and a forward current (I_F) of 20 mA, unless otherwise stated. Tolerances are critical for design: Luminous Intensity (±11%), Dominant Wavelength (±1 nm), and Forward Voltage (±0.10V).

For S2 (Brilliant Orange):

• Luminous Intensity (I_v): 36.0 - 112 mcd (see binning).
• Peak Wavelength (λ_p): 611 nm (typical).
• Dominant Wavelength (λ_d): 599.0 - 611.0 nm.
• Spectral Bandwidth (Δλ): 17 nm (typical).
• Forward Voltage (V_F): 1.75 - 2.35 V.
• Reverse Current (I_R): 10 μA max at V_R=5V.

For G6 (Brilliant Yellow Green):

• Luminous Intensity (I_v): 16.0 - 45.0 mcd (see binning).
• Peak Wavelength (λ_p): 575 nm (typical).
• Dominant Wavelength (λ_d): 568.5 - 574.5 nm.
• Spectral Bandwidth (Δλ): 20 nm (typical).
• Forward Voltage (V_F): 1.75 - 2.35 V.
• Reverse Current (I_R): 10 μA max at V_R=5V.

Common Parameter:

• Viewing Angle (2θ_1/2): 120 degrees (typical) for both variants.

3. Binning System Explanation

To ensure color and brightness consistency in production, the LEDs are sorted into bins based on luminous intensity and dominant wavelength.

3.1 S2 (Orange) Binning

Luminous Intensity Bins (at I_F=20mA):

• Bin 1: 36 - 72 mcd
• Bin 2: 72 - 112 mcd

Dominant Wavelength Bins (at I_F=20mA):

• Bin 1: 599 - 605 nm
• Bin 2: 605 - 611 nm

3.2 G6 (Yellow-Green) Binning

Luminous Intensity Bins (at I_F=20mA):

• Bin 1: 16.0 - 28.5 mcd
• Bin 2: 28.5 - 36.0 mcd
• Bin 3: 36.0 - 45.0 mcd

Dominant Wavelength Bins (at I_F=20mA):

• Bin 1: 568.5 - 570.5 nm
• Bin 2: 570.5 - 572.5 nm
• Bin 3: 572.5 - 574.5 nm

4. Performance Curve Analysis

The datasheet provides typical characteristic curves for both LED types, which are essential for understanding device behavior under different operating conditions.

4.1 Forward Current vs. Luminous Intensity

These curves show that luminous intensity increases with forward current but not linearly. Designers must operate within the specified current limits to avoid accelerated degradation. The derating curves illustrate how the maximum allowable forward current decreases as the ambient temperature rises above 25°C, which is critical for thermal management.

4.2 Forward Current vs. Forward Voltage (IV Curve)

The IV curve demonstrates the diode's exponential relationship. The forward voltage (V_F) has a negative temperature coefficient, meaning it decreases slightly as the junction temperature increases. This must be considered in constant-current driver design.

4.3 Spectral Distribution

The spectrum plots confirm the monochromatic nature of the LEDs. The S2 chip emits in the orange region centered around 611 nm, while the G6 chip emits in the yellow-green region around 575 nm. The narrow bandwidth (FWHM of ~17-20 nm) indicates high color purity.

4.4 Radiation Pattern

The polar diagram confirms the wide 120-degree viewing angle, providing a broad, Lambertian-like emission pattern suitable for area illumination and wide-angle indicators.

5. Mechanical & Packaging Information

5.1 Package Dimensions

The LED has a compact rectangular footprint. Key dimensions (in mm, tolerance ±0.1mm unless noted) are: Length=1.6, Width=0.8, Height=0.5. The cathode is marked for polarity identification. A recommended solder pad layout is provided (0.7mm x 0.8mm for pads, 0.3mm gap), but this should be optimized based on specific PCB design rules and soldering processes.

5.2 Reel, Tape, and Moisture-Sensitive Packaging

The components are supplied in carrier tape on 7-inch reels, with a standard loaded quantity of 3000 pieces per reel. Detailed reel and tape dimensions are provided for feeder compatibility. The LEDs are packaged in a moisture-resistant aluminum bag with desiccant to prevent moisture absorption, which is critical for preventing \"popcorn\" cracking during reflow soldering.

6. Soldering & Assembly Guidelines

6.1 Soldering Profile

The device is rated for lead-free reflow soldering with a peak temperature of 260°C for a maximum of 10 seconds. A standard reflow profile with appropriate pre-heating, ramp-up, peak, and cooling stages should be followed. Hand soldering is permissible at 350°C for up to 3 seconds, but care must be taken to avoid thermal shock.

6.2 Storage and Handling Precautions

Over-Current Protection: An external current-limiting resistor is mandatory. LEDs are current-driven devices; a small voltage change can cause a large current surge, leading to immediate failure.

Moisture Sensitivity: This is a Moisture Sensitivity Level (MSL) component. The unopened bag must be stored at ≤30°C and ≤90% RH. Once opened, the \"floor life\" is 1 year under conditions of ≤30°C and ≤60% RH. Unused parts must be resealed in a moisture-proof bag with desiccant. If the desiccant indicator shows saturation or the storage time is exceeded, a bake-out at 60±5°C for 24 hours is required before reflow.

7. Label and Ordering Information

The label on the reel provides key traceability and technical data: Customer Part Number (CPN), Manufacturer Part Number (P/N), Packing Quantity (QTY), Luminous Intensity Rank (CAT), Chromaticity/Dominant Wavelength Rank (HUE), Forward Voltage Rank (REF), and Lot Number (LOT No.). This information is crucial for quality control and ensuring the correct components are used in production.

8. Application Design Considerations

8.1 Driver Circuit Design

Always use a constant-current driver or a voltage source with a series resistor. Calculate the resistor value using R = (V_supply - V_F) / I_F, considering the worst-case V_F from the datasheet to ensure I_F never exceeds 25 mA. For precision applications, select bins for intensity and wavelength to achieve uniform appearance across multiple LEDs.

8.2 Thermal Management

Although power dissipation is low (60mW), proper PCB layout is essential. Use thermal vias under the LED's thermal pad (if applicable) and ensure adequate copper area to dissipate heat, especially in high ambient temperature environments or when driving at higher currents. Adhere to the forward current derating curve.

8.3 Optical Design

The wide 120-degree viewing angle makes these LEDs suitable for applications requiring broad illumination without secondary optics. For focused light, external lenses or light guides may be necessary. The clear resin package provides good light extraction.

9. Technical Comparison & Differentiation

The 18-225 series differentiates itself through its use of AlGaInP (Aluminum Gallium Indium Phosphide) semiconductor material. This material system is highly efficient for producing high-brightness red, orange, amber, and yellow-green light, offering superior performance and stability compared to older technologies like GaAsP. The combination of small size, high reliability, and compliance with modern environmental standards (RoHS, Halogen-Free) makes it a preferred choice for contemporary electronic designs over larger, leaded alternatives.

10. Frequently Asked Questions (FAQ)

Q: Can I drive this LED directly from a 3.3V or 5V logic supply?

A: No. You must use a series current-limiting resistor. For example, with a 3.3V supply and a typical V_F of 2.0V at 20mA, R = (3.3V - 2.0V) / 0.020A = 65 Ohms. Use the maximum V_F (2.35V) for a safer calculation.

Q: What is the difference between peak wavelength and dominant wavelength?

A: Peak wavelength (λ_p) is the wavelength at the highest intensity point in the spectrum. Dominant wavelength (λ_d) is the single wavelength of monochromatic light that matches the perceived color of the LED. λ_d is more relevant for color specification.

Q: Why is baking necessary before soldering?

A: Plastic packages can absorb moisture. During the high-temperature reflow process, this moisture turns to steam rapidly, creating internal pressure that can crack the package (\"popcorn effect\"). Baking removes this absorbed moisture.

11. Practical Design Case Study

Scenario: Designing a status indicator panel with 10 uniformly bright orange indicators.

1. Component Selection: Choose the S2 (Orange) variant. For uniformity, specify tight binning for both luminous intensity (e.g., Bin 2: 72-112 mcd) and dominant wavelength (e.g., Bin 1: 599-605 nm).
2. Circuit Design: The system uses a 5V rail. Using the max V_F of 2.35V and target I_F of 20mA, calculate R = (5V - 2.35V) / 0.02A = 132.5 Ohms. Use the nearest standard value of 130 or 150 Ohms. A 150 Ohm resistor gives I_F ≈ 17.7mA, which is within spec and provides a safety margin.
3. Layout: Place the LEDs on a 0.05\" (1.27mm) grid. Follow the recommended solder pad dimensions but adjust the gap to 0.25mm to match the PCB manufacturer's capabilities. Include a small ground copper pour around each LED for minor heat dissipation.
4. Assembly: Ensure the factory bag is sealed upon receipt. Schedule PCB assembly within the 1-year floor life after opening. If exceeded, bake the reels before sending to the assembly house.

12. Technology Principle Introduction

This LED is based on an AlGaInP (Aluminum Gallium Indium Phosphide) heterostructure grown on a substrate. When a forward voltage is applied, electrons and holes are injected into the active region where they recombine, releasing energy in the form of photons (light). The specific color (orange or yellow-green) is determined by the bandgap energy of the semiconductor material in the active region, which is controlled by the precise ratios of aluminum, gallium, and indium. The light is emitted through a clear epoxy resin lens that also provides environmental protection.

13. Industry Trends

The trend in SMD LEDs continues toward higher efficiency (more lumens per watt), smaller package sizes for increased density, and improved color consistency and rendering. There is also a strong drive for broader adoption of environmentally friendly materials and manufacturing processes. While this 18-225 series represents a mature and reliable technology, newer generations may utilize advanced phosphor-converted designs or different semiconductor materials like InGaN for broader color gamuts. However, AlGaInP remains the dominant and most efficient technology for the orange-red-yellow spectrum.