SMD LED 24-21/BHC-AP1Q2/2A Datasheet - Blue - 2.0x1.25x0.8mm - 3.3V - 20mA - English Technical Document

1. Product Overview

The 24-21 SMD LED is a compact, surface-mount device designed for modern electronic applications requiring miniaturization and high reliability. This blue LED, based on InGaN chip technology, offers a balance of performance and size, making it suitable for automated assembly processes.

1.1 Core Advantages and Positioning

The primary advantage of this component is its significantly reduced footprint compared to traditional lead-frame LEDs. This enables smaller printed circuit board (PCB) designs, higher component packing density, and ultimately contributes to the development of more compact end-user equipment. Its lightweight construction further enhances its suitability for miniature and portable applications.

1.2 Target Market and Applications

This LED is targeted at general lighting and indication markets. Key application areas include backlighting for instrument panels, switches, and symbols; status indicators and backlighting in telecommunication devices such as telephones and fax machines; and general-purpose illumination where a compact blue light source is required.

2. Key Features and Compliance

• Packaged in 8mm tape on 7-inch diameter reels for compatibility with automated pick-and-place equipment.
• Designed for use with standard infrared and vapor phase reflow soldering processes.
• Mono-color (Blue) type.
• Constructed with Pb-free materials.
• The product complies with the RoHS directive.
• Compliance with EU REACH regulations is maintained.
• Halogen-free construction: Bromine (Br) <900 ppm, Chlorine (Cl) <900 ppm, Br+Cl < 1500 ppm.

3. Technical Parameters: In-Depth Objective Interpretation

3.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed and should be avoided for reliable performance.

• Reverse Voltage (V_R): 5V. Exceeding this voltage in reverse bias can cause junction breakdown.
• Forward Current (I_F): 20mA. The recommended continuous operating current.
• Peak Forward Current (I_FP): 40mA. Permissible only under pulsed conditions (duty cycle 1/10 @ 1kHz).
• Power Dissipation (P_d): 75mW. The maximum power the package can dissipate at 25°C ambient.
• Electrostatic Discharge (ESD): 150V (Human Body Model). Proper ESD handling precautions are essential.
• Operating Temperature (T_opr): -40°C to +85°C. The ambient temperature range for normal operation.
• Storage Temperature (T_stg): -40°C to +90°C.
• Soldering Temperature (T_sol): Reflow: 260°C peak for 10 seconds max. Hand soldering: 350°C for 3 seconds max per terminal.

3.2 Electro-Optical Characteristics

Measured at T_a = 25°C and I_F = 20mA, unless otherwise specified. These are the key performance parameters under standard test conditions.

• Luminous Intensity (I_v): 45.0 to 112.0 mcd (millicandela). The specific output is determined by the bin code (P1, P2, Q1, Q2). A tolerance of ±11% applies.
• Viewing Angle (2θ_1/2): Typically 130 degrees. This defines the angular spread where intensity is at least half of the peak value.
• Peak Wavelength (λ_p): Typically 468 nm. The wavelength at which the spectral emission is strongest.
• Dominant Wavelength (λ_d): 464.5 to 476.5 nm. This defines the perceived color of the light and is binned (A9-A12). A tolerance of ±1nm applies.
• Spectral Bandwidth (Δλ): Typically 25 nm. The width of the emission spectrum at half the maximum intensity.
• Forward Voltage (V_F): 2.7V to 3.7V, with a typical value of 3.3V at 20mA.
• Reverse Current (I_R): Maximum 50 μA at V_R = 5V. The device is not designed for operation in reverse bias.

4. Binning System Explanation

To ensure color and brightness consistency in production, LEDs are sorted into bins.

4.1 Luminous Intensity Binning

Bins define the minimum and maximum luminous output at I_F=20mA. P1: 45.0 - 57.0 mcd P2: 57.0 - 72.0 mcd Q1: 72.0 - 90.0 mcd Q2: 90.0 - 112.0 mcd

3.2 Dominant Wavelength Binning

Bins define the range of the dominant wavelength, which correlates to the shade of blue. A9: 464.5 - 467.5 nm A10: 467.5 - 470.5 nm A11: 470.5 - 473.5 nm A12: 473.5 - 476.5 nm

5. Performance Curve Analysis

The datasheet provides several characteristic curves measured at T_a=25°C. These are essential for understanding device behavior under non-standard conditions.

5.1 Forward Current vs. Forward Voltage (I-V Curve)

This curve shows the exponential relationship between current and voltage. The typical forward voltage is 3.3V at 20mA. Designers must use a current-limiting resistor to prevent thermal runaway, as a small increase in voltage can cause a large, potentially destructive increase in current.

5.2 Relative Luminous Intensity vs. Forward Current

Luminous intensity increases with forward current, but not linearly. Operating above the recommended 20mA may yield higher output but will reduce efficiency and device lifetime due to increased junction temperature.

5.3 Relative Luminous Intensity vs. Ambient Temperature

LED light output decreases as ambient temperature rises. This curve is critical for applications operating in elevated temperature environments, as it allows designers to derate the expected output or implement thermal management.

5.4 Forward Current Derating Curve

This graph defines the maximum allowable continuous forward current as a function of ambient temperature. To ensure reliability, the operating current must be reduced when the ambient temperature exceeds 25°C.

5.5 Spectrum Distribution

The emission spectrum is centered around 468 nm (blue) with a typical bandwidth of 25 nm. This information is vital for optical system design and color-sensitive applications.

5.6 Radiation Pattern

The polar diagram illustrates the spatial distribution of light intensity, confirming the 130-degree viewing angle. The pattern is typically Lambertian or near-Lambertian for this type of package.

6. Mechanical and Package Information

6.1 Package Dimensions

The 24-21 SMD package has nominal dimensions of 2.0mm (length) x 1.25mm (width) x 0.8mm (height). The detailed mechanical drawing specifies all critical dimensions, including pad size (0.6mm x 0.55mm), spacing (1.0mm between pad centers), and component tolerances (typically ±0.1mm unless otherwise noted).

6.2 Polarity Identification

The cathode is typically marked, often by a notch, a green dot, or a different pad shape on the carrier tape. The datasheet's package drawing should be consulted for the specific marking scheme.

7. Soldering and Assembly Guidelines

7.1 Reflow Soldering Profile

A lead-free reflow profile is recommended: - Preheat: 150-200°C for 60-120 seconds. - Time above liquidus (217°C): 60-150 seconds. - Peak temperature: 260°C maximum, held for 10 seconds maximum. - Heating rate: Maximum 6°C/sec up to 255°C. - Cooling rate: Maximum 3°C/sec. Reflow soldering should not be performed more than two times.

7.2 Hand Soldering

If hand soldering is necessary: - Use a soldering iron with a tip temperature less than 350°C. - Limit contact time to 3 seconds per terminal. - Use an iron with a power rating less than 25W. - Allow a minimum of 2 seconds between soldering each terminal to avoid thermal shock.

7.3 Storage and Moisture Sensitivity

The components are packaged in moisture-resistant barrier bags with desiccant. - Do not open the bag until ready for use. - After opening, unused LEDs must be stored at ≤30°C and ≤60% Relative Humidity. - The "floor life" after bag opening is 168 hours (7 days). - If exceeded, or if the desiccant indicator has changed color, a bake-out at 60±5°C for 24 hours is required before reflow.

8. Packaging and Ordering Information

8.1 Reel and Tape Specifications

The LEDs are supplied in embossed carrier tape with a width of 8mm, wound on a standard 7-inch diameter reel. Each reel contains 2000 pieces. Detailed reel, carrier tape, and cover tape dimensions are provided in the datasheet.

8.2 Label Explanation

The reel label contains several codes: - CPN: Customer's Product Number. - P/N: Manufacturer's Product Number (e.g., 24-21/BHC-AP1Q2/2A). - QTY: Packing Quantity. - CAT: Luminous Intensity Bin Code (e.g., Q2). - HUE: Dominant Wavelength Bin Code (e.g., A10). - REF: Forward Voltage Rank. - LOT No: Traceable manufacturing lot number.

9. Application Suggestions and Design Considerations

9.1 Current Limiting

An external current-limiting resistor is mandatory. The value can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet (3.7V) for a worst-case design to ensure the current does not exceed 20mA even with component tolerances.

9.2 Thermal Management

While the package is small, thermal considerations are important for longevity. Ensure adequate copper area on the PCB under and around the LED pads to act as a heat sink, especially when operating at high ambient temperatures or near maximum current.

9.3 Optical Design

The 130-degree viewing angle provides wide illumination. For focused light, secondary optics (lenses) are required. The spectrum is suitable for backlighting color filters or for use as a pure blue indicator.

10. Technical Comparison and Differentiation

The 24-21 package offers a smaller footprint than traditional 3mm or 5mm through-hole LEDs, enabling higher-density designs. Compared to other SMD LEDs like the 0402 or 0603, the 24-21 (approx. 0805 metric) typically offers higher light output and better thermal performance due to its larger size, while remaining significantly smaller than high-power LED packages. Its compatibility with standard reflow processes differentiates it from devices requiring special handling.

11. Frequently Asked Questions (Based on Technical Parameters)

11.1 What resistor should I use with a 5V supply?

Using the typical V_F of 3.3V and I_F of 20mA: R = (5V - 3.3V) / 0.02A = 85 Ohms. For a robust design using the max V_F of 3.7V: R = (5V - 3.7V) / 0.02A = 65 Ohms. A standard 68 or 75 Ohm resistor would be appropriate. Always calculate power rating: P = I²R.

11.2 Can I drive this LED without a resistor using a constant current source?

Yes, a constant current driver set to 20mA is an excellent method that eliminates variations due to V_F tolerance and supply voltage fluctuations, offering more consistent brightness and better longevity.

11.3 Why is the luminous intensity given as a range?

Due to inherent variations in semiconductor manufacturing, LEDs are sorted (binned) by output. The specific bin (P1, P2, Q1, Q2) on the reel label tells you the guaranteed minimum and maximum intensity for that batch.

11.4 How do I interpret the wavelength bins?

The dominant wavelength bin (A9-A12) ensures color consistency. For example, bin A10 (467.5-470.5 nm) will produce a slightly different shade of blue than bin A12 (473.5-476.5 nm). For uniform appearance in an array, specify and use LEDs from the same wavelength and intensity bins.

12. Practical Use Case Example

Scenario: Designing a low-power status indicator for a portable consumer device. Design Choices: The 24-21 LED is selected for its small size and suitability for reflow soldering. A blue color is chosen for a "power-on" indicator. The device runs on a 3.3V regulated rail. Calculation: Using a typical V_F of 3.3V at 20mA would require near-zero voltage drop, making current control impossible. Therefore, the LED is driven at a lower current, e.g., 10mA, for adequate visibility while saving power. Using the typical V_F curve, V_F at 10mA is approximately 3.1V. Resistor R = (3.3V - 3.1V) / 0.01A = 20 Ohms. A 22 Ohm resistor is selected. The power dissipation in the LED is P = V_F * I_F ≈ 3.1V * 0.01A = 31mW, well within the 75mW rating.

13. Operating Principle Introduction

This is a semiconductor light-emitting diode. When a forward voltage exceeding the junction's built-in potential is applied, electrons and holes are injected across the p-n junction. In the active region, these charge carriers recombine, releasing energy in the form of photons. The specific material used (Indium Gallium Nitride - InGaN) determines the bandgap energy and thus the wavelength (color) of the emitted light, which in this case is in the blue spectrum. The epoxy resin package serves to protect the semiconductor chip, provide mechanical stability, and acts as a primary lens shaping the light output.

14. Technology Trends

The development of SMD LEDs like the 24-21 follows broader industry trends towards miniaturization, increased efficiency (lumens per watt), and higher reliability. Advancements in InGaN material quality have enabled brighter and more consistent blue LEDs. Packaging technology continues to evolve to improve thermal management in smaller form factors, allowing for higher drive currents and greater luminous output from compact devices. The standardization of footprints and soldering profiles facilitates their integration into automated, high-volume manufacturing processes.