SMD LED 91-21SYGC/S530-XX/XXX Datasheet - 2.0x1.25x1.1mm - 2.0V - 40mW - Brilliant Yellow Green - English Technical Document

1. Product Overview

The 91-21 series is a surface-mount device (SMD) LED designed for modern, compact electronic applications. This component utilizes AlGaInP semiconductor technology to produce a Brilliant Yellow Green light output, encapsulated in a water-clear resin. Its primary design goal is to enable miniaturization and high-density board layouts while maintaining reliable performance.

1.1 Core Advantages and Product Positioning

The key advantage of the 91-21 LED is its significantly reduced footprint compared to traditional leaded components. This enables smaller printed circuit board (PCB) designs, higher component packing density, reduced storage space requirements, and ultimately contributes to the development of smaller end-user equipment. Its light weight makes it particularly suitable for miniature and portable applications. Furthermore, the component is designed for compatibility with automated pick-and-place assembly equipment, which ensures high placement accuracy and manufacturing efficiency.

1.2 Target Market and Applications

This LED is targeted at a wide range of consumer, industrial, and office electronics requiring compact, reliable indicator or backlighting solutions. Typical application scenarios include, but are not limited to:

• Status indicators for indoor equipment.
• Backlighting for LCD panels, membrane switches, and control panel symbols.
• Indicator and backlight functions in office automation equipment (e.g., printers, scanners).
• Battery status indicators and keypad backlighting in portable, battery-driven devices.
• Indicator lights and display backlighting in audio/video equipment.
• Dashboard and switch backlighting in automotive or control panel contexts.
• Indicator and backlighting functions in telecommunication devices such as telephones and fax machines.

2. Technical Specifications and In-Depth Interpretation

This section provides a detailed breakdown of the electrical, optical, and thermal parameters that define the operational boundaries and performance of the LED.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation at or near these limits is not recommended for extended periods.

• Reverse Voltage (V_R): 5 V. Exceeding this voltage in reverse bias can cause junction breakdown.
• Continuous Forward Current (I_F): 20 mA. This is the recommended maximum DC operating current.
• Peak Forward Current (I_FP): 60 mA. Permissible only under pulsed conditions (duty cycle 1/10 @ 1 kHz).
• Power Dissipation (P_d): 60 mW. The maximum power the package can dissipate, calculated as V_F * I_F.
• Operating Temperature (T_opr): -40°C to +85°C. The ambient temperature range for reliable operation.
• Storage Temperature (T_stg): -40°C to +100°C.
• Electrostatic Discharge (ESD): Withstands 2000 V (Human Body Model). Proper ESD handling procedures are essential.
• Soldering Temperature: Reflow: 260°C peak for 10 seconds max. Hand soldering: 350°C for 3 seconds max per terminal.

2.2 Electro-Optical Characteristics (T_a = 25°C)

These parameters describe the typical performance of the LED under specified test conditions.

• Luminous Intensity (I_v): Measured at I_F = 20 mA. Available in multiple ranks (E1 to E4), with typical values ranging from 198 mcd to 630 mcd. A ±11% tolerance applies.
• Viewing Angle (2θ_1/2): 25 degrees. This defines the angular spread where luminous intensity is at least half of the peak intensity.
• Peak Wavelength (λ_p): 575 nm (typical). The wavelength at which the spectral power distribution is maximum.
• Dominant Wavelength (λ_d): 573 nm (typical) with a tolerance of ±1 nm. This is the single wavelength perceived by the human eye as the color of the light.
• Spectral Bandwidth (Δλ): 20 nm (typical). The width of the emitted spectrum at half the maximum intensity.
• Forward Voltage (V_F): 2.0 V (typical), ranging from 1.7 V to 2.4 V at I_F = 20 mA, with a ±0.1V tolerance on the typical value.
• Reverse Current (I_R): 10 μA (maximum) at V_R = 5 V.

3. Binning System Explanation

The product is categorized into different performance bins to ensure consistency in application design. The selection guide indicates the primary binning parameters.

3.1 Luminous Intensity Binning (CAT)

The luminous output is sorted into ranks labeled E1 through E4, as detailed in the Electro-Optical Characteristics table. Designers must select the appropriate rank based on the required brightness for their application, considering the specified minimum and typical values.

3.2 Wavelength Binning (HUE)

The dominant wavelength is controlled to a tight tolerance of ±1 nm around the typical value of 573 nm. This ensures very consistent color perception across different production lots and units.

3.3 Forward Voltage Binning (REF)

The forward voltage is also binned, with a typical value of 2.0V and a tolerance of ±0.1V. This information is crucial for designing the current-limiting circuitry, especially in battery-powered applications where voltage headroom is limited.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet, the following analysis is based on standard LED behavior and the provided parameters.

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

The LED exhibits a typical forward voltage of 2.0V at 20mA. Like all diodes, the V_F has a negative temperature coefficient, meaning it decreases slightly as junction temperature increases. The specified V_F range (1.7V-2.4V) must be accounted for in the driver design to ensure proper current regulation.

4.2 Luminous Intensity vs. Forward Current

Luminous intensity is approximately proportional to forward current within the operating range. Operating above the absolute maximum current (20mA DC) will increase light output but will also generate more heat, potentially leading to accelerated lumen depreciation or catastrophic failure.

4.3 Temperature Characteristics

The LED's luminous output typically decreases as the junction temperature rises. The wide operating temperature range (-40°C to +85°C) indicates robust performance, but designers should consider thermal management if operating at high ambient temperatures or high drive currents to maintain consistent brightness.

5. Mechanical and Package Information

5.1 Package Outline Dimensions (91-21)

The component has a compact SMD footprint. Key dimensions (in mm) include a typical package size. The cathode is typically identified by a marking or a specific pad geometry (e.g., a notch or a green marking as indicated in the label explanation). Precise dimensional drawings are provided in the datasheet for PCB land pattern design.

5.2 Polarity Identification

Correct polarity is critical. The datasheet indicates polarity identification markings on the package. The cathode is typically marked. Designers must ensure the PCB footprint matches this orientation.

6. Soldering and Assembly Guidelines

Adherence to these guidelines is essential for reliability and to prevent damage during the assembly process.

6.1 Reflow Soldering Profile (Pb-free)

A recommended temperature profile is provided:

• Pre-heating: 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.
• Time Above 255°C: 30 seconds maximum.
• Heating/Cooling Rate: Maximum 3°C/sec (heating), 6°C/sec (cooling).

6.2 Hand Soldering

If hand soldering is unavoidable, use a soldering iron with a tip temperature below 350°C, applying heat to each terminal for no more than 3 seconds. Use a low-power iron (≤25W) and allow an interval of at least 2 seconds between soldering each terminal to prevent thermal shock.

6.3 Moisture Sensitivity and Storage

The LEDs are packaged in moisture-barrier bags.

• Before opening: Store at ≤30°C and ≤90% RH.
• After opening: The "floor life" is 72 hours at ≤30°C and ≤60% RH. Unused parts must be resealed in a moisture-proof package with desiccant.
• Baking: If the storage time is exceeded or the desiccant indicates moisture, bake at 60±5°C for 24 hours before use.

7. Packaging and Ordering Information

7.1 Standard Packaging

The device is supplied in 12mm wide embossed carrier tape on 7-inch diameter reels, compatible with automated assembly equipment. Bulk packaging of 1000 pieces per bag is also available.

7.2 Label Explanation

The reel or package label contains several key identifiers:

• CPN: Customer's Product Number.
• P/N: Manufacturer's Product Number (e.g., 91-21SYGC/S530-XX/XXX).
• LOT No.: Traceable manufacturing lot number.
• QTY: Quantity of pieces in the package.
• CAT, HUE, REF: Codes for Luminous Intensity, Dominant Wavelength, and Forward Voltage ranks, respectively.

8. Application Design Considerations

8.1 Current Limiting is Mandatory

An external current-limiting resistor is absolutely required. The LED's exponential I-V characteristic means a small increase in forward voltage can cause a large, potentially destructive increase in current. The resistor value (R) can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Always use the maximum V_F from the datasheet for a conservative design that ensures I_F does not exceed 20mA under worst-case conditions.

8.2 Thermal Management

Although power dissipation is low (max 60mW), ensuring adequate heat sinking through the PCB pads is good practice, especially in high ambient temperature environments or when driving at the maximum current. This helps maintain stable light output and long-term reliability.

8.3 ESD Protection

With an ESD withstand rating of 2000V, standard ESD precautions during handling and assembly are necessary. Incorporating transient voltage suppression on sensitive lines in the end application may be required in harsh environments.

9. Technical Comparison and Differentiation

The 91-21 LED differentiates itself through its combination of a very small 2.0x1.25mm footprint, relatively high luminous intensity for its size (up to 630 mcd typ.), and the specific Brilliant Yellow Green color produced by the AlGaInP chip material. Compared to older through-hole LEDs, it offers massive space savings. Compared to other SMD LEDs, its key advantages are the clear resin for maximum light extraction and the well-defined viewing angle, making it suitable for both indicator and backlighting roles where a directed beam is beneficial.

10. Frequently Asked Questions (FAQ)

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

Using the formula R = (V_supply - V_F) / I_F, and assuming a worst-case V_F of 2.4V and target I_F of 20mA: R = (5V - 2.4V) / 0.02A = 130 Ohms. The nearest standard higher value (e.g., 150 Ohms) would provide a margin of safety, resulting in a current of approximately 17.3mA.

10.2 Can I drive this LED without a resistor using a constant voltage source?

No. This will almost certainly destroy the LED. The forward voltage is not a fixed value but a characteristic of the diode junction. A constant voltage source set to the typical V_F (2.0V) will not regulate current, and minor variations or temperature changes will lead to uncontrolled current flow.

10.3 How do I identify the cathode?

Refer to the package outline drawing in the datasheet. The cathode is typically indicated by a green marking on the top or side of the package, or by a specific feature in the pad layout (e.g., the cathode pad may be square while the anode is round, or vice-versa).

11. Practical Design and Usage Case

Scenario: Designing a low-battery indicator for a portable device. The device uses a 3.3V regulated supply. The goal is to have an LED illuminate brightly when the battery is low. A 91-21 LED from the E3 bin (400-630 mcd) is selected for good visibility. Calculation: R = (3.3V - 2.4V) / 0.02A = 45 Ohms. A 47 Ohm standard resistor is chosen. The microcontroller's GPIO pin, configured as an open-drain output, sinks the current to ground to turn the LED on. The compact size of the 91-21 allows it to fit into a very small area on the crowded PCB of the portable device.

12. Operating Principle

The LED operates on the principle of electroluminescence in a semiconductor p-n junction. The chip material is Aluminum Gallium Indium Phosphide (AlGaInP). When a forward voltage exceeding the junction's built-in potential is applied, electrons from the n-type region and holes from the p-type region are injected into the active region where they recombine. This recombination event releases energy in the form of photons (light). The specific composition of the AlGaInP alloy determines the bandgap energy, which in turn defines the wavelength (color) of the emitted light, in this case, Brilliant Yellow Green (~573 nm). The water-clear epoxy resin encapsulant protects the chip and acts as a lens, shaping the light output into the specified 25-degree viewing angle.

13. Technology Trends

The 91-21 LED represents a mature and reliable technology within the broader trend of electronics miniaturization. The ongoing development in SMD LEDs focuses on several key areas: increasing luminous efficacy (more light output per watt of electrical input), improving color consistency and color rendering index (CRI) for lighting applications, developing ever-smaller package sizes (e.g., 01005, micro-LEDs), and enhancing reliability under higher temperature and humidity conditions. Furthermore, integration of control electronics directly with the LED die (e.g., IC-driven LEDs) is a growing trend for smart lighting applications. The 91-21, with its focus on a specific color and compact indicator/backlight role, remains a fundamental and widely used component within this evolving landscape.