SMD LED 15-21/S2C-AQ2R2B/2T Specification - Brilliant Orange - 20mA - 60mW - English Technical Document

1. Product Overview

The 15-21/S2C-AQ2R2B/2T is a surface-mount device (SMD) LED utilizing AlGaInP (Aluminum Gallium Indium Phosphide) semiconductor technology to emit a Brilliant Orange color. This component is designed for high-density PCB applications where space and weight are critical constraints. Its compact form factor enables significant reductions in board size and equipment dimensions compared to traditional lead-frame type LEDs.

The LED is packaged on 8mm tape wound onto a 7-inch diameter reel, making it fully compatible with automated pick-and-place assembly equipment. It is a mono-color type, compliant with Pb-free, RoHS, EU REACH, and halogen-free regulations (Br <900 ppm, Cl <900 ppm, Br+Cl < 1500 ppm). The device is suitable for both infrared and vapor phase reflow soldering processes.

2. Technical Parameter Deep Dive

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed.

• Reverse Voltage (VR): 5 V. Exceeding this voltage in reverse bias can cause junction breakdown.
• Continuous Forward Current (IF): 25 mA. The maximum DC current for reliable operation.
• Peak Forward Current (IFP): 60 mA. This is permissible only under pulsed conditions with a duty cycle of 1/10 at 1 kHz. It should not be used for continuous operation.
• Power Dissipation (Pd): 60 mW. The maximum power the package can dissipate at an ambient temperature (Ta) of 25°C. This value derates with increasing temperature.
• Electrostatic Discharge (ESD) Human Body Model (HBM): 2000 V. This indicates the device's sensitivity to static electricity. Proper ESD handling procedures are mandatory.
• Operating Temperature (Topr): -40°C to +85°C. The ambient temperature range over which the device is specified to operate.
• Storage Temperature (Tstg): -40°C to +90°C.
• Soldering Temperature: The device can withstand reflow soldering with a peak temperature of 260°C for up to 10 seconds, or hand soldering at 350°C for up to 3 seconds per terminal.

2.2 Electro-Optical Characteristics

These parameters are measured at a standard test condition of Ta=25°C and IF=20 mA, unless otherwise specified. They define the optical and electrical performance of the LED.

• Luminous Intensity (Iv): Ranges from 90.0 mcd (minimum) to 180.0 mcd (maximum), with a typical tolerance of ±11%. This is the perceived brightness of the light source.
• Viewing Angle (2θ1/2): Typically 130 degrees. This is the full angle at which the luminous intensity is half of the intensity at 0 degrees (on-axis).
• Peak Wavelength (λp): Typically 611 nm. The wavelength at which the spectral power distribution is maximum.
• Dominant Wavelength (λd): Ranges from 600.5 nm to 612.5 nm. This is the single wavelength that best matches the perceived color of the LED, with a tolerance of ±1 nm.
• Spectral Bandwidth (Δλ): Typically 17 nm. The width of the spectrum at half the maximum intensity (FWHM).
• Forward Voltage (VF): Ranges from 1.75 V (minimum) to 2.35 V (maximum) at 20 mA, with a tolerance of ±0.1V.
• Reverse Current (IR): Maximum 10 μA when a reverse voltage (VR) of 5V is applied. The device is not designed for operation in reverse bias.

3. Binning System Explanation

To ensure color and brightness consistency in production, LEDs are sorted into bins based on key parameters. The part number 15-21/S2C-AQ2R2B/2T contains bin codes (A, Q2, R2, B).

3.1 Luminous Intensity Binning

LEDs are categorized by their measured luminous intensity at IF=20mA.

• Bin Q2: 90.0 mcd to 112.0 mcd
• Bin R1: 112.0 mcd to 140.0 mcd
• Bin R2: 140.0 mcd to 180.0 mcd

The "R2" in the part number indicates this device falls into the highest brightness bin for this series.

3.2 Dominant Wavelength Binning

LEDs are sorted by their dominant wavelength to control color hue.

• Bin D8: 600.5 nm to 603.5 nm
• Bin D9: 603.5 nm to 606.5 nm
• Bin D10: 606.5 nm to 609.5 nm
• Bin D11: 609.5 nm to 612.5 nm

The "A" in the part number likely corresponds to one of these wavelength bins (e.g., D10 or D11 for a typical orange).

3.3 Forward Voltage Binning

Sorting by forward voltage helps in designing consistent current drive circuits.

• Bin 0: 1.75 V to 1.95 V
• Bin 1: 1.95 V to 2.15 V
• Bin 2: 2.15 V to 2.35 V

The "B" in the part number indicates the forward voltage bin.

4. Performance Curve Analysis

The datasheet provides several characteristic curves that are crucial for understanding the LED's behavior under different operating conditions.

4.1 Relative Luminous Intensity vs. Forward Current

This curve shows that light output is not linearly proportional to current. It increases sub-linearly at higher currents due to efficiency droop and thermal effects. Operating significantly above the recommended 20mA may yield diminishing returns in brightness and reduce lifetime.

4.2 Relative Luminous Intensity vs. Ambient Temperature

The luminous intensity decreases as the ambient temperature increases. This is a characteristic of semiconductor LEDs. The curve allows designers to estimate brightness loss in elevated temperature environments, which is critical for applications like automotive dashboards.

4.3 Forward Current Derating Curve

This graph defines the maximum allowable continuous forward current as a function of ambient temperature. As temperature rises, the maximum current must be reduced to stay within the device's power dissipation limits and prevent thermal runaway.

4.4 Forward Voltage vs. Forward Current

This IV (Current-Voltage) curve shows the exponential relationship typical of a diode. The voltage increases logarithmically with current. The curve is essential for designing the current-limiting resistor or constant-current driver.

4.5 Radiation Diagram and Spectrum Distribution

The radiation diagram (polar plot) visually represents the 130-degree viewing angle. The spectrum distribution plot confirms the monochromatic nature of the AlGaInP LED, showing a single peak around 611 nm with a typical FWHM of 17 nm.

5. Mechanical and Package Information

5.1 Package Dimensions

The 15-21 SMD LED has a compact rectangular package. Key dimensions (in mm, tolerance ±0.1mm unless noted) include the overall length, width, and height. The datasheet provides a detailed drawing showing the chip placement, lens shape, and lead frame. A cathode mark is clearly indicated on the package for correct polarity orientation during assembly.

5.2 Polarity Identification

Correct polarity is essential. Applying reverse voltage exceeding 5V can instantly damage the LED. The package features a distinct cathode identifier (typically a green dot, a notch, or a chamfered corner) as shown in the dimension drawing. Designers must ensure the PCB footprint matches this orientation.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

A lead-free reflow profile is specified:

• Pre-heating: 150–200°C for 60–120 seconds.
• Time Above Liquidus (TAL): Above 217°C for 60–150 seconds.
• Peak Temperature: Maximum of 260°C, held for a maximum of 10 seconds.
• Heating Rate: Maximum 6°C/sec.
• Time Above 255°C: Maximum 30 seconds.
• Cooling Rate: Maximum 3°C/sec.

Reflow soldering should not be performed more than two times on the same device.

6.2 Hand Soldering

If hand soldering is necessary, extreme care is required:

• Use a soldering iron with a tip temperature less than 350°C.
• Limit contact time to a maximum of 3 seconds per terminal.
• Use an iron with a power rating of 25W or less.
• Allow an interval of at least 2 seconds between soldering each terminal.

Hand soldering poses a high risk of thermal damage.

6.3 Storage and Moisture Sensitivity

The LEDs are packaged in a moisture-resistant barrier bag with desiccant.

• Do not open the bag until ready for use.
• After opening, unused LEDs should be stored at ≤30°C and ≤60% Relative Humidity.
• The "floor life" after bag opening is 168 hours (7 days).
• If the exposure time is exceeded or the desiccant indicator has changed color, a bake-out at 60 ±5°C for 24 hours is required before reflow to prevent "popcorn" damage during soldering.

6.4 Critical Precautions

• Current Limiting: An external current-limiting resistor is MANDATORY. The LED's exponential V-I characteristic means a small voltage change causes a large current change, leading to immediate burnout without a resistor.
• Mechanical Stress: Avoid applying stress to the LED body during soldering or in the final application. Do not warp the PCB after assembly.
• Repair: Repair after soldering is strongly discouraged. If absolutely necessary, use a dual-head soldering iron to simultaneously heat both terminals and lift the component evenly to avoid pad damage. Verify LED functionality after any repair attempt.

7. Packaging and Ordering Information

7.1 Reel and Tape Specifications

The device is supplied in embossed carrier tape on a 7-inch (178mm) diameter reel.

• Carrier Tape Width: 8 mm.
• Pocket Pitch: As per the detailed dimension drawing.
• Quantity per Reel: 2000 pieces.

Detailed drawings for the reel, carrier tape, and cover tape dimensions are provided with tolerances of ±0.1mm unless specified.

7.2 Label Explanation

The reel label contains critical information for traceability and correct application:

• CPN: Customer's Product Number.
• P/N: Manufacturer's Product Number (e.g., 15-21/S2C-AQ2R2B/2T).
• QTY: Packing Quantity.
• CAT: Luminous Intensity Rank (e.g., R2).
• HUE: Chromaticity/Dominant Wavelength Rank (e.g., A).
• REF: Forward Voltage Rank (e.g., B).
• LOT No: Manufacturing Lot Number for traceability.

8. Application Suggestions

8.1 Typical Application Scenarios

• Automotive Interior: Backlighting for dashboard instruments, switches, and control panels.
• Telecommunications Equipment: Status indicators and keypad backlighting in phones and fax machines.
• Consumer Electronics: Flat backlighting for small LCD displays, switch illumination, and symbolic indicators.
• General Indicator Use: Any application requiring a compact, bright, orange status indicator.

8.2 Design Considerations

• Drive Circuit: Always use a series resistor or constant-current driver. Calculate the resistor value using R = (Vsupply - VF) / IF, where VF should be chosen from the maximum bin value (2.35V) for a robust design.
• Thermal Management: While the package is small, ensure adequate PCB copper area or thermal vias if operating near maximum current or in high ambient temperatures, as heat reduces light output and lifespan.
• Optical Design: The 130-degree viewing angle provides a wide beam. For more focused light, external lenses or light pipes may be required.
• ESD Protection: Implement ESD protection on input lines if the LED is in a user-accessible location, even though the device has a 2kV HBM rating.

9. Technical Comparison and Differentiation

Compared to older through-hole LEDs or larger SMD packages, the 15-21 offers distinct advantages:

• Size & Weight: Its miniature footprint allows for higher packing density and lighter end products, crucial for portable and miniaturized devices.
• Automation Compatibility: The tape-and-reel packaging is optimized for high-speed, automated assembly, reducing manufacturing costs.
• Performance: The use of AlGaInP material provides high luminous efficiency in the orange/red spectrum range compared to older technologies.
• Compliance: Full compliance with modern environmental regulations (RoHS, Halogen-Free, REACH) is built-in, simplifying the compliance process for end products.

A potential consideration is thermal performance; the very small size can limit heat dissipation compared to larger packages with more thermal mass.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 What resistor value should I use with a 5V supply?

Using the maximum forward voltage (2.35V) from Bin 2 and the recommended current (20mA): R = (5V - 2.35V) / 0.020A = 132.5 Ohms. The nearest standard value of 130 Ohms or 150 Ohms would be appropriate. Always verify actual current in the circuit.

10.2 Can I drive this LED at 30mA for more brightness?

No. The Absolute Maximum Rating for continuous forward current (IF) is 25 mA. Operating at 30 mA exceeds this rating, which will significantly reduce reliability and lifespan, and may cause immediate failure. Use the peak current (60mA pulsed) only for very short duty cycles if necessary.

10.3 Why does the brightness drop when the board gets hot?

This is a fundamental characteristic of LED semiconductors, as shown in the "Relative Luminous Intensity vs. Ambient Temperature" curve. Increased temperature increases non-radiative recombination within the semiconductor, reducing efficiency. Proper thermal design mitigates this effect.

10.4 The bag was opened a month ago. Can I still use the LEDs?

Not without precaution. The moisture sensitivity level requires use within 168 hours (7 days) of bag opening. If exceeded, you must bake the LEDs at 60°C for 24 hours before subjecting them to reflow soldering to drive out absorbed moisture and prevent internal delamination during the high-temperature soldering process.

11. Practical Design and Usage Case

Case: Designing a Status Indicator Panel
A designer is creating a control panel with 20 orange status indicators. They choose the 15-21/S2C-AQ2R2B/2T for its brightness (R2 bin) and compact size.

1. Circuit Design: A common 5V rail is used. Using a conservative VF of 2.35V, a 150-ohm current-limiting resistor is selected for each LED, resulting in a current of ~17.7mA, safely below the 25mA maximum.
2. PCB Layout: The compact footprint allows all 20 LEDs to fit in a single row. The cathode mark on the footprint is clearly aligned with the package drawing to prevent assembly errors.
3. Manufacturing: The tape-and-reel packaging allows the PCB assembler to use automated pick-and-place machines, ensuring fast, accurate, and reliable population of all 20 components.
4. Result: The panel has uniform, bright orange indicators with consistent color (thanks to wavelength binning) and brightness (thanks to intensity binning), manufactured efficiently and reliably.

12. Principle Introduction

The 15-21 LED is based on AlGaInP (Aluminum Gallium Indium Phosphide) semiconductor material. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the active region. Their recombination releases energy in the form of photons (light). The specific composition of the AlGaInP alloy determines the bandgap energy, which directly defines the wavelength (color) of the emitted light—in this case, brilliant orange (~611 nm). The epoxy resin lens encapsulates the semiconductor die, provides mechanical protection, and shapes the light output pattern to achieve the specified 130-degree viewing angle.

13. Development Trends

The evolution of SMD LEDs like the 15-21 follows several key industry trends:

• Miniaturization: Continuous reduction in package size (e.g., from 0603 to 0402 to 0201 metric sizes) to enable ever-smaller electronic devices.
• Increased Efficiency: Ongoing improvements in epitaxial growth and chip design yield higher luminous efficacy (more light output per electrical watt), reducing power consumption and thermal load.
• Enhanced Reliability: Improvements in packaging materials and die attach technologies lead to longer operational lifetimes and better performance under harsh conditions (high temperature, humidity).
• Advanced Binning: Tighter binning tolerances for color (wavelength) and flux are becoming standard, driven by applications requiring high color consistency, such as full-color displays and automotive lighting clusters.
• Integration: A trend towards integrating multiple LED chips (RGB, or white + color) into a single package, or incorporating control ICs for "smart LED" modules.

While the 15-21 represents a mature and reliable technology, newer packages may offer smaller footprints or higher efficiency, but the fundamental principles of operation and key application guidelines remain largely consistent.