SMD LED 91-21SUGC/S400-A4/TR7 Datasheet - 2.0x1.25x1.1mm - 3.5V - 25mA - Brilliant Green - English Technical Document

1. Product Overview

The 91-21SUGC/S400-A4/TR7 is a surface-mount device (SMD) LED designed for compact, high-density electronic assemblies. It features a brilliant green light output using InGaN chip technology encapsulated in a water-clear resin. Its miniature footprint enables significant reductions in PCB size and equipment dimensions, making it ideal for space-constrained applications.

1.1 Key Features and Advantages

• Miniaturization: The package is significantly smaller than traditional leaded components, facilitating smaller board designs, higher component packing density, and reduced storage requirements.
• Automation Compatibility: Supplied on 12mm tape on 7-inch reels, it is fully compatible with automated pick-and-place assembly equipment, ensuring high placement accuracy and manufacturing efficiency.
• Environmental Compliance: The product is Pb-free, compliant with RoHS, EU REACH, and halogen-free standards (Br <900ppm, Cl <900ppm, Br+Cl <1500ppm).
• Lightweight Design: Its minimal weight is advantageous for portable and miniature electronic devices.
• Standardized Package: Conforms to EIA standard packaging for broad industry compatibility.

2. Technical Specifications and In-Depth Interpretation

2.1 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.

• Reverse Voltage (V_R): 5V. Exceeding this voltage in reverse bias can cause junction breakdown.
• Forward Current (I_F): 25mA DC. The continuous operating current should not exceed this value.
• Peak Forward Current (I_FP): 100mA at a duty cycle of 1/10 and 1kHz frequency. Suitable for pulsed operation but not for DC.
• Power Dissipation (P_d): 95mW. The maximum power the package can dissipate, calculated as V_F * I_F.
• Operating & Storage Temperature: -40°C to +85°C (operating), -40°C to +90°C (storage). Ensures reliability across a wide environmental range.
• Electrostatic Discharge (ESD): 150V (Human Body Model). Requires standard ESD handling precautions during assembly.
• Soldering Temperature: Withstands reflow soldering at 260°C for 10 seconds or hand soldering at 350°C for 3 seconds per terminal.

2.2 Electro-Optical Characteristics @ T_a=25°C

These are the typical performance parameters under standard test conditions (I_F=20mA).

• Luminous Intensity (I_v): 2000-2300 mcd (Typical). This high brightness is suitable for indicator and backlight applications.
• Viewing Angle (2θ_1/2): 25° (Typical). A relatively narrow viewing angle, providing directed light output.
• Peak Wavelength (λ_p): 518 nm (Typical). The wavelength at which the spectral emission is strongest.
• Dominant Wavelength (λ_d): 525 nm (Typical). The perceived color of the light.
• Spectral Bandwidth (Δλ): 35 nm (Typical). The range of wavelengths emitted, centered around the peak.
• Forward Voltage (V_F): 3.5V (Typical), 4.3V (Max) @ 20mA. A constant current driver or series resistor is mandatory to limit current, as V_F has a negative temperature coefficient.
• Reverse Current (I_R): 50 µA (Max) @ V_R=5V. The device is not designed for reverse operation; this parameter is for test purposes only.

3. Binning System Explanation

The datasheet indicates the use of a binning system for key parameters, as referenced in the label explanation (CAT, HUE, REF). This system ensures color and brightness consistency within a defined range.

• Luminous Intensity Rank (CAT): Bins the LED based on its measured luminous output (e.g., 2000-2300 mcd is likely one bin).
• Dominant Wavelength Rank (HUE): Bins the LED based on its dominant wavelength (e.g., around 525nm), controlling the precise shade of green.
• Forward Voltage Rank (REF): Bins the LED based on its forward voltage drop at a specified current, aiding in circuit design for consistent current drive.

4. Performance Curve Analysis

The datasheet references "Typical Electro-Optical Characteristics Curves." While not displayed in the provided text, such curves typically include:

• Relative Luminous Intensity vs. Forward Current: Shows how light output increases with current, typically in a near-linear relationship before saturation.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the derating of light output as junction temperature increases.
• Forward Voltage vs. Forward Current: The diode's IV characteristic curve.
• Forward Voltage vs. Ambient Temperature: Shows the negative temperature coefficient of V_F.
• Spectral Distribution: A graph plotting intensity against wavelength, showing the peak at ~518nm and bandwidth of ~35nm.

5. Mechanical and Package Information

5.1 Package Outline Dimensions

The 91-21 package has nominal dimensions of 2.0mm (L) x 1.25mm (W) x 1.1mm (H). Tolerances are ±0.1mm unless otherwise specified. The drawing details the cathode identifier, lens shape, and terminal locations.

5.2 Polarity Identification

The package includes a visual marker (typically a notch or a green dot on the cathode side) to identify the cathode terminal, which is crucial for correct PCB orientation.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile (Pb-free)

• Pre-heating: 150-200°C for 60-120 seconds. Max ramp-up rate: 3°C/sec.
• 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.
• Cooling Rate: Maximum 6°C/sec.
• Reflow Cycles: Maximum of two times.

6.2 Hand Soldering

If necessary, use a soldering iron with a tip temperature <350°C, capacity <25W, and limit contact time to 3 seconds per terminal. Allow a 2-second interval between soldering each terminal.

6.3 Storage and Moisture Sensitivity

This component is moisture-sensitive (MSL).

• Before Opening: Store at ≤30°C / ≤90% RH.
• After Opening (Floor Life): 72 hours at ≤30°C / ≤60% RH.
• Rebaking: If the desiccant indicator changes or floor life is exceeded, bake at 60±5°C for 24 hours before use.

6.4 Critical Precautions

• Current Limiting: An external series resistor is mandatory to prevent thermal runaway and burnout due to the negative temperature coefficient of V_F.
• Stress Avoidance: Avoid mechanical stress on the LED during soldering and do not warp the PCB after assembly.
• Repair: Not recommended. If unavoidable, use a dual-head soldering iron to simultaneously heat both terminals and avoid thermal shock. Verify performance after repair.

7. Packaging and Ordering Information

7.1 Packaging Specifications

• Carrier Tape: 12mm width, 7-inch diameter reel.
• Quantity per Reel: 1000 pieces.
• Moisture-Resistant Bag: Packed with desiccant in a sealed aluminum moisture-proof bag.

7.2 Label Explanation

The reel label contains the following information: Customer's Product Number (CPN), Product Number (P/N), Lot Number (LOT No.), Packing Quantity (QTY), and the Binning Codes for Luminous Intensity (CAT), Dominant Wavelength (HUE), and Forward Voltage (REF).

8. Application Suggestions

8.1 Typical Application Scenarios

• Status indicators in consumer electronics (audio/video equipment, battery-powered devices).
• Backlighting for LCD panels, membrane switches, and instrument symbols.
• Indicator and backlighting in office automation equipment (printers, scanners).
• Dashboard and control panel switch backlighting in automotive interiors.
• Indicator lights in telecommunication devices (phones, fax machines).

8.2 Design Considerations

• Driver Circuit: Always use a constant current source or a current-limiting resistor in series with the LED. Calculate the resistor value using R = (V_supply - V_F) / I_F.
• Thermal Management: While low-power, ensure adequate PCB copper area or thermal vias if operating at high ambient temperatures or maximum current to maintain junction temperature within limits.
• ESD Protection: Implement ESD protection on input lines if the LED is exposed to user interfaces.
• Optical Design: The 25° viewing angle provides a focused beam. Consider light pipes or diffusers if wider illumination is needed.

9. Technical Comparison and Differentiation

Compared to older through-hole LEDs or larger SMD packages, the 91-21 offers:

• Size Advantage: One of the smallest standardized SMD LED packages, enabling ultra-miniaturization.
• Brightness Efficiency: High luminous intensity for its size and power consumption, thanks to InGaN technology.
• Automation Readiness: Tape-and-reel packaging optimized for high-speed assembly, reducing manufacturing cost versus manual insertion.
• Compliance Lead: Full compliance with modern environmental regulations (RoHS, REACH, Halogen-Free) is a standard requirement but remains a key differentiator against non-compliant legacy parts.

10. Frequently Asked Questions (FAQs)

Q1: Why is a series resistor absolutely necessary?
A1: The forward voltage (V_F) decreases as the LED's junction temperature rises. Without a current-limiting element, a small increase in supply voltage or decrease in V_F can cause a large, uncontrolled increase in current, leading to rapid overheating and failure.

Q2: Can I drive this LED with a 5V supply directly?
A2: No. With a typical V_F of 3.5V, connecting it directly to 5V would attempt to pass a very high current, destroying it instantly. A series resistor is required. For example, targeting I_F=20mA: R = (5V - 3.5V) / 0.02A = 75Ω (use nearest standard value, e.g., 75Ω or 82Ω).

Q3: What does the "Floor Life" of 72 hours mean?
A3: After the moisture-proof bag is opened, the components can be exposed to factory ambient conditions (≤30°C/60% RH) for up to 72 hours before they must be soldered. Exceeding this time risks popcorn cracking during reflow due to absorbed moisture vaporizing. Unused parts must be re-dried (rebaked).

Q4: How do I identify the correct polarity?
A4: Refer to the package outline drawing. The cathode is typically marked by a green dot on the top or a notch/chamfer on one side of the package. The PCB footprint silkscreen should mirror this marking.

11. Practical Design and Usage Case

Scenario: Designing a low-battery indicator for a portable device.
The LED needs to be bright, small, and low power. The 91-21SUGC is an excellent choice.
Implementation: Use a microcontroller GPIO pin to drive the LED. The pin can sink/source up to 20mA. Connect the LED anode to the GPIO pin via a current-limiting resistor. Connect the cathode to ground. Calculate the resistor value based on the MCU's V_OH (e.g., 3.3V). R = (3.3V - 3.5V) / 0.02A = -10Ω. This negative value indicates 3.3V is insufficient to forward bias the LED to 20mA. Solution: Either drive the LED at a lower current (e.g., 10mA: R = (3.3V-3.5V)/0.01A, still problematic) or use the GPIO to control a transistor switch connected to a higher voltage rail (e.g., the battery voltage) with an appropriate series resistor. This case highlights the importance of matching driver voltage to LED V_F.

12. Operating Principle Introduction

This LED is based on an Indium Gallium Nitride (InGaN) semiconductor chip. When a forward voltage exceeding the diode's junction potential is applied, electrons and holes are injected into the active region where they recombine. In this material system, the energy released during recombination is emitted as photons (light). The specific composition of the InGaN alloy determines the bandgap energy, which directly corresponds to the wavelength (color) of the emitted light—in this case, brilliant green (~525 nm). The water-clear epoxy resin acts as a protective encapsulant and a primary lens, shaping the light output beam.

13. Technology Trends

The development of SMD LEDs like the 91-21 package follows several key industry trends: Miniaturization continues to drive package sizes down while maintaining or improving optical output. Increased Efficiency through advancements in epitaxial growth and chip design leads to higher lumens per watt. Enhanced Reliability is achieved with improved packaging materials and thermal management designs. Broader Color Gamuts in display backlighting are pushing for LEDs with narrower spectral bandwidths and more precise wavelength control. Integration is another trend, with multi-chip packages (RGB, white) and LED drivers being combined into single modules. The 91-21 represents a mature, highly optimized point in the evolution of single-color, indicator-class SMD LEDs.