SMD LED 27-21 Pure White Datasheet - Package Size 2.7x2.1mm - Voltage 2.7-3.15V - Power 40mW - Technical Documentation

1. Product Overview

27-21 SMD LED is a compact surface-mount light-emitting diode designed for modern electronic applications requiring miniaturization and high reliability. Compared to traditional lead-frame type LEDs, this component represents a significant technological advancement, enabling substantial reduction in circuit board space usage, increased packaging density, and ultimately contributing to the development of smaller, more efficient end-user devices. Its lightweight structure makes it particularly suitable for application scenarios where space and weight are critical limiting factors.

This LED emits pure white light, achieved through the InGaN (Indium Gallium Nitride) chip material encapsulated within a yellow diffusing resin. This combination provides uniform and diffused light output, suitable for various indicator and backlighting functions. The product fully complies with contemporary environmental and safety standards, including RoHS (Restriction of Hazardous Substances), the EU REACH regulation, and is manufactured as a halogen-free component, with bromine and chlorine content maintained below specified limits.

2. Technical Specifications and Objective Interpretation

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation under or beyond these conditions is not guaranteed and should be avoided in circuit design.

• Reverse voltage (V_R):5V. Exceeding this voltage under reverse bias may cause junction breakdown.
• Forward current (I_F):10mA (continuous). This is the maximum recommended DC current for ensuring long-term reliable operation.
• Peak Forward Current (I_FP):100mA. This current is only permitted under pulse conditions (duty cycle 1/10 @ 1kHz) and must not be used for continuous drive.
• Power Dissipation (P_d):40mW. This is the maximum power that can be dissipated by the package without exceeding its thermal limit, calculated as forward voltage (V_F) * forward current (I_F).
• Electrostatic Discharge (ESD) Human Body Model (HBM):150V. This indicates that the device has moderate sensitivity to ESD; appropriate handling procedures must be taken (e.g., grounded workstation, ESD-safe packaging).
• Operating temperature (T_opr):-40°C to +85°C. This device is suitable for the industrial temperature range.
• Storage Temperature (T_stg):-40°C to +90°C.
• Soldering Temperature (T_sol):Compatible with standard reflow soldering temperature profile (peak 260°C for 10 seconds) and hand soldering (maximum 350°C per terminal for up to 3 seconds).

2.2 Electro-Optical Characteristics

These parameters are measured under standard test conditions of 25°C ambient temperature and 5mA forward current, serving as a common reference point for comparison and binning.

• Luminous intensity (I_v):57.0 - 112 mcd. The wide range reflects the binning process, where LEDs are sorted into specific output groups (P2, Q1, Q2). A typical value is not explicitly given and falls within this binning range.
• Viewing angle (2θ_1/2):140 degrees (typical). This wide viewing angle is a characteristic of the yellow diffused resin, which scatters light, making the LED suitable for applications requiring broad illumination rather than a focused beam.
• Forward Voltage (V_F):2.70V - 3.15V. This is the voltage drop across the LED when driven at 5mA. LEDs are also binned according to their forward voltage range (code 15, 16, 17). A tolerance of ±0.1V is specified.
• Reverse current (I_R):At V_R=5V, maximum 50 µA. This parameter is for test purposes only; the device is not intended for reverse bias operation.

Important note:The datasheet explicitly warns that reverse voltage conditions are for test purposes only; LEDs must not be operated under reverse bias. Designers must ensure correct polarity in the circuit.

3. Grading System Description

To ensure consistency in mass production, LEDs are tested against key performance parameters and sorted into different "bins." This allows designers to select components with tightly controlled characteristics for their specific application requirements.

3.1 Luminous Intensity Binning

LEDs are categorized into three bins based on their light output at 5mA.

• Bin P2:57.0 - 72.0 mcd
• Gear Q1:72.0 - 90.0 mcd
• Gear Q2:90.0 - 112 mcd

A general tolerance of ±11% for luminous intensity is also specified.

3.2 Forward Voltage Binning

To assist current regulation design, LEDs are also binned according to their forward voltage drop:

• Bin 15:2.70V - 2.85V
• Gear 16:2.85V - 3.00V
• Gear 17:3.00V - 3.15V

The tolerance of forward voltage is ±0.1V.

3.3 Chromaticity Coordinate Binning

To ensure color consistency, the white light output is binned according to its coordinates on the CIE 1931 chromaticity diagram. The datasheet defines six bins (1 to 6), each specifying a quadrilateral area on the x, y color coordinate chart with a tolerance of ±0.01. This precise binning ensures that all LEDs within a selected bin will exhibit nearly identical white color points, which is crucial for applications where color uniformity is critical, such as backlight arrays.

4. Performance Curve Analysis

Although the PDF references "typical photoelectric characteristic curves," specific charts (e.g., I_Vversus I_Frelationship, I_Vversus temperature relationship, spectral distribution) are not detailed in the provided text. Typically, such curves would display:

• Luminous Intensity vs. Forward Current (I_V-I_F):A nonlinear relationship where light output increases with current but may saturate or degrade at higher currents exceeding the rated maximum.
• Luminous Intensity vs. Ambient Temperature (I_V-T_a):Light output typically decreases as junction temperature increases. This curve quantifies this derating and is crucial for thermal management in applications.
• Forward Voltage vs. Junction Temperature (V_F-T_j): V_FTypically has a negative temperature coefficient, decreasing as temperature increases.
• Spectral Power Distribution:A chart showing the relative intensity of light across the entire visible wavelength spectrum, defining the color quality of "white" (e.g., cool white, warm white).

When an LED operates outside the standard 5mA/25°C test conditions, designers should refer to these curves to accurately predict performance.

5. Mechanical and Packaging Information

5.1 Package Size

The 27-21 SMD LED features a compact package size. The dimension drawing illustrates the package dimensions, with a tolerance of ±0.1mm unless otherwise specified. Key features visible in the diagram include the component outline, electrode pad locations, and polarity marking (likely a cathode indicator). Precise dimensions (length, width, height) are crucial for PCB pad pattern design and ensuring correct placement by automated equipment.

5.2 Polarity Identification

The package includes a marking to identify the cathode (negative) terminal. Correct polarity must be observed during assembly to prevent device damage from reverse bias.

6. Welding and Assembly Guide

6.1 Reflow Soldering Temperature Profile

This LED is compatible with infrared and vapor phase reflow processes. The recommended lead-free reflow soldering temperature profile is provided:

• Preheat:150-200°C, for 60-120 seconds.
• Time above liquidus (217°C):60-150 seconds.
• Peak Temperature:Maximum 260°C, maintain for no more than 10 seconds.
• Heating Rate:Maximum 6°C/s.
• Time above 255°C:Maximum 30 seconds.
• Cooling rate:Maximum 3°C/second.

Critical rule:No more than two reflow soldering processes should be performed on the same LED component.

6.2 Manual Soldering

If manual welding must be performed:

• Use a soldering iron with a tip temperature below 350°C.
• Limit the contact time for each terminal to within 3 seconds.
• Use a soldering iron with a capacity of 25W or lower.
• Weld each terminal with at least a 2-second interval between them to manage thermal stress.

The datasheet warns that damage often occurs during manual soldering, so extra caution is required.

6.3 Storage and Moisture-proof Requirements

LEDs are packaged with moisture-proof materials (the carrier tape is placed in an aluminum moisture-proof bag with desiccant).

• Before opening:Store at ≤30°C and ≤90% relative humidity (RH).
• After opening:Under conditions of ≤30°C and ≤60% RH, the "shop floor life" is 1 year. Unused components should be resealed in moisture barrier packaging.
• Baking:If the desiccant indicator shows saturation or the storage time is exceeded, the LEDs should be baked at 60 ±5°C for 24 hours before use to remove absorbed moisture and prevent the "popcorn" phenomenon during reflow soldering.

7. Packaging and Ordering Information

7.1 Reel Specifications

LEDs are supplied in industry-standard packaging for automated assembly:

• Carrier Tape:8mm wide carrier tape, wound on a 7-inch diameter reel.
• Quantity:3000 pieces per reel.
• Detailed dimensional drawings of the carrier tape and reel are provided, with a standard tolerance of ±0.1mm.

7.2 Label Description

The reel label contains several key codes for traceability and specification.

• P/N:Product number (e.g., 27-21/T3D-AP2Q2HY/3C).
• QTY:Packaging quantity.
• CAT:Luminous intensity grade (e.g., P2, Q1, Q2).
• HUE:Chromaticity coordinates and dominant wavelength grade (e.g., grade 1-6).
• REF:Forward voltage grade (e.g., 15, 16, 17).
• LOT No:Production batch number, used for traceability.

8. Application Suggestions

8.1 Typical Application Scenarios

The datasheet lists several major applications that take advantage of the LED's small size, diffused light, and reliability:

• Backlighting:Used for instrument panels, switches, and keyboards.
• Telecommunications equipment:Serves as status indicator lights and backlights in telephones and fax machines.
• LCD Display:Provides flat, uniform backlighting for small LCD panels, switch legends, and symbols.
• General Indicator Light:Any application requiring compact, bright, white indicator lights.

8.2 Design Considerations and Precautions

The datasheet contains critical warnings to ensure reliable operation:

• Current limiting is mandatory:An external current-limiting resistor must always be used in series with the LED. The forward voltage has a slight negative temperature coefficient, meaning V_Fdecreases slightly as the LED heats up. Without a resistor, this can lead to a significant increase in current (thermal runaway), potentially destroying the LED. The resistor stabilizes the current.
• Avoid mechanical stress:During soldering or final assembly, do not apply stress to the LED body. Avoid PCB bending after soldering.
• Rework:It is strongly not recommended to rework or repair the circuit board after the LED is soldered. If absolutely necessary, use a dedicated dual-tip soldering iron to heat both terminals simultaneously to minimize thermal stress. Single-point reheating may cause damage.
• ESD Protection:Due to the device's 150V HBM rating, standard ESD precautions must be implemented during handling and assembly.

9. Technical Comparison and Differentiation

Although the datasheet does not provide a direct comparison with other specific LED models, the 27-21 package offers distinct advantages in specific scenarios:

• Compared to leaded LEDs:The main advantages are a significant reduction in PCB space occupation and weight, enabling modern miniaturized electronic products. It also eliminates the need for lead bending and insertion, simplifying automated assembly.
• Compared to larger SMD LEDs (e.g., 3528, 5050):The 27-21 offers a smaller footprint for ultra-compact designs, although it may involve trade-offs in total light output or thermal dissipation capability compared to larger packages.
• Compared to LEDs with clear lenses:Yellow diffused resin provides a wider viewing angle (140°) and a softer, more uniform appearance, making it superior in applications where LEDs are viewed directly, while clear lenses produce a more focused beam.

Its compliance with RoHS, REACH, and halogen-free standards is a fundamental requirement for modern components, yet it remains a key differentiator compared to older, non-compliant inventory products.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 Why is it necessary to connect a current-limiting resistor in series?

LED is a current-driven device, not voltage-driven. Its V-I curve is very steep. A small change in forward voltage (which may be caused by temperature variation or manufacturing differences) can lead to a large change in current. The series resistor acts as a simple linear current regulator, stabilizing the operating point and preventing thermal runaway and LED damage.

10.2 What does the bin code (P2, Q1, 15, 16, etc.) mean for my design?

Binning ensures product consistency. If your design requires uniform brightness among multiple LEDs (e.g., in a backlight array), you should specify LEDs from the same luminous intensity bin (CAT). If your power supply voltage margin is tight, specifying a tighter forward voltage bin (REF) is helpful. For applications with strict color requirements, specifying a chromaticity bin (HUE) is crucial. Using unbinned or mixed-bin LEDs may lead to visible brightness or color differences in the final product.

10.3 Can I continuously drive this LED with a 10mA current?

Yes, 10mA is the rated maximum continuous forward current. However, operating at absolute maximum ratings may reduce long-term reliability and increase junction temperature. For optimal lifespan and stability, it is recommended to drive the LED at a test current of 5mA or below, especially in cases of limited thermal management.

10.4 Pembe ya maono ni digrii 140. Je, mwanga unatolewa sawasawa ndani ya pembe hii?

"Viewing Angle" (2θ_1/2) is defined as the angle at which the luminous intensity drops to half of its value at 0 degrees (on-axis). The yellow diffusing resin produces a near-Lambertian emission pattern, with intensity highest on-axis and decreasing towards the edges. Compared to a clear lens LED, it provides excellent uniformity for wide-angle viewing but cannot achieve perfect uniformity across the full 140° range.

11. Usanifu halisi na Mifano ya Matumizi

Scenario: Designing a backlit membrane switch panel.

1. Component Selection:The 27-21 LED was chosen for its small size (suitable for placement behind switch icons), diffused light (providing even illumination), and surface-mount compatibility (suitable for automated assembly onto the switch PCB).
2. Circuit Design:Select a constant current of 5mA to balance brightness and lifespan. Use a 3.3V power supply, and assume V_Ffrom gear 16 (typical value 2.93V), calculate the series resistance: R = (V_{Power Supply}- V_F) / I_F= (3.3V - 2.93V) / 0.005A = 74 ohms. Select a standard 75-ohm resistor.
3. PCB Layout:Pad patterns shall be designed strictly according to the package dimension drawing. Maintain sufficient clearance between the LED and the film layer.
4. Procurement:When ordering LEDs, specify brightness bin Q1 and chromaticity bin 2 or 3 to ensure consistent white color point across all switches on the panel.
5. Assembly:Components are stored in sealed bags before use. The PCB undergoes a single reflow soldering process using the specified temperature profile. Avoid applying stress to the LEDs during handling.

12. Introduction to Working Principles

27-21 LED is a solid-state light source based on a semiconductor p-n junction. The active region uses an InGaN (indium gallium nitride) compound semiconductor. When a forward voltage exceeding the diode's turn-on threshold (forward voltage, V_F) is applied, electrons and holes are injected into the active region and recombine within it. In direct bandgap semiconductors like InGaN, this recombination primarily releases energy in the form of photons (light). The specific bandgap energy of the InGaN alloy determines the wavelength of the emitted light. To generate white light from the blue/UV-emitting InGaN chip, a yellow phosphor (contained within the yellow diffusing resin package) is used. A portion of the blue light emitted by the chip is absorbed by the phosphor and re-emitted as yellow light. The remaining blue light mixes with the converted yellow light, which is perceived as white by the human eye. The diffusing resin contains scattering particles that randomize the direction of emitted photons, resulting in a wide, uniform viewing angle.

13. Teknoloji Trendleri ve Gelişimi

SMD LEDs like the 27-21 represent a mature and widely adopted technology. Current industry trends focus on several key areas that build upon this foundation:

• Improving efficiency (lumens per watt):Continuous advancements in epitaxial growth, chip design, and phosphor technology continue to drive improvements in luminous efficacy. This enables brighter light output at the same current or achieves lower power consumption and reduced heat generation for the same light output.
• Improving color quality and consistency:Advances in phosphor formulations and more precise binning techniques (e.g., using 3-5 step MacAdam ellipses for tighter color control) have enabled LEDs to achieve higher Color Rendering Index (CRI) and greater color point consistency between batches.
• Miniaturization:The pursuit of smaller devices continues to drive further reductions in package size (e.g., 2016, 1515) while maintaining or improving optical performance.
• Enhanced Reliability and Lifespan:Research on better packaging materials and thermal management technologies aims to improve the operational lifespan and stability of LEDs, especially under high-temperature or high-humidity conditions.
• Integrated Solutions:The trend is moving towards LEDs with integrated drivers, controllers, and even multi-color chips (RGB) in a single package, simplifying circuit design for end-users.

The 27-21 LED, with its standardized package and well-defined characteristics, serves as a reliable workhorse component within this evolving technological landscape.