SMD LED LTST-C950KGKT Datasheet - AlInGaP Green - 25mA - 62.5mW - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a high-brightness, surface-mount LED designed for automated assembly processes. The device utilizes an advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor chip to produce green light, offering superior luminous efficiency and reliability in a compact package. It is engineered for integration into space-constrained electronic applications where consistent performance and ease of manufacturing are critical.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Incorporates a dome lens design for optimized light output and viewing angle.
• Utilizes an ultra-bright AlInGaP chip technology.
• Supplied in industry-standard 8mm tape on 7-inch diameter reels for automated pick-and-place equipment.
• Compatible with standard infrared (IR) reflow soldering processes.
• Logic-level compatible drive current.

1.2 Applications

This LED is suitable for a broad range of indicator and backlighting functions across multiple industries, including:

• Telecommunication equipment (e.g., cellular phones, network switches).
• Office automation devices (e.g., printers, scanners).
• Consumer home appliances.
• Industrial control panels and equipment.
• Keypad and keyboard backlighting.
• Status and power indicators.
• Micro-displays and symbolic luminaries.

2. Package Dimensions

The LED is housed in a standard surface-mount device (SMD) package. The lens color is water clear, and the light source is an AlInGaP chip emitting green light. All dimensional tolerances are ±0.1 mm unless otherwise specified. Refer to the dimensional drawings in the original datasheet for precise measurements of the component body, cathode identifier, and pad layout.

3. Ratings and Characteristics

3.1 Absolute Maximum Ratings

Stresses beyond these limits may cause permanent damage to the device. All ratings are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): 62.5 mW
• Peak Forward Current (I_F(peak)): 60 mA (at 1/10 duty cycle, 0.1ms pulse width)
• Continuous Forward Current (I_F): 25 mA DC
• Reverse Voltage (V_R): 5 V
• Operating Temperature Range: -30°C to +85°C
• Storage Temperature Range: -40°C to +85°C
• Infrared Reflow Soldering Condition: 260°C peak temperature for a maximum of 10 seconds.

3.2 Electrical and Optical Characteristics

Typical performance parameters measured at Ta=25°C and I_F=20mA, unless noted.

• Luminous Intensity (I_V): 280 - 1120 mcd (millicandela). The specific value is determined by the bin rank.
• Viewing Angle (2θ_1/2): 25 degrees (the off-axis angle where intensity is half the on-axis value).
• Peak Emission Wavelength (λ_P): 574.0 nm (typical).
• Dominant Wavelength (λ_d): 564.5 - 576.5 nm (dependent on bin).
• Spectral Line Half-Width (Δλ): 15 nm (typical).
• Forward Voltage (V_F): 1.8 - 2.4 V.
• Reverse Current (I_R): 10 µA maximum at V_R=5V.

Measurement Notes: Luminous intensity is measured using a sensor filtered to match the CIE photopic eye-response curve. The dominant wavelength is derived from the CIE chromaticity diagram.

3.3 Electrostatic Discharge (ESD) Caution

This device is sensitive to electrostatic discharge and electrical surges. Proper ESD control measures must be implemented during handling and assembly. Recommendations include the use of grounded wrist straps, anti-static gloves, and ensuring all equipment and workstations are properly grounded.

4. Bin Rank System

To ensure color and brightness consistency in production, devices are sorted into bins based on key parameters. This allows designers to select LEDs matching their specific tolerance requirements.

4.1 Forward Voltage (V_F) Rank

Binned at I_F=20mA. Tolerance per bin is ±0.1V.

• D2: 1.8V (Min) - 2.0V (Max)
• D3: 2.0V (Min) - 2.2V (Max)
• D4: 2.2V (Min) - 2.4V (Max)

4.2 Luminous Intensity (I_V) Rank

Binned at I_F=20mA. Tolerance per bin is ±15%.

• T: 280.0 mcd (Min) - 450.0 mcd (Max)
• U: 450.0 mcd (Min) - 710.0 mcd (Max)
• V: 710.0 mcd (Min) - 1120.0 mcd (Max)

4.3 Hue (Dominant Wavelength, λ_d) Rank

Binned at I_F=20mA. Tolerance per bin is ±1 nm.

• B: 564.5 nm (Min) - 567.5 nm (Max)
• C: 567.5 nm (Min) - 570.5 nm (Max)
• D: 570.5 nm (Min) - 573.5 nm (Max)
• E: 573.5 nm (Min) - 576.5 nm (Max)

5. Typical Performance Curves

The datasheet includes graphical representations of key characteristics under typical conditions (25°C unless noted). These curves are essential for understanding device behavior under different operating conditions.

• Relative Luminous Intensity vs. Forward Current: Shows how light output increases with drive current, typically in a sub-linear relationship that highlights efficiency changes.
• Forward Voltage vs. Forward Current: Illustrates the diode's I-V characteristic, crucial for designing current-limiting circuits.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the thermal derating of light output, which is critical for high-temperature or high-power applications.
• Spectral Distribution: Depicts the relative radiant power as a function of wavelength, centered around the peak wavelength, showing the narrow bandwidth typical of AlInGaP LEDs.

6. User Guide and Assembly Information

6.1 Cleaning

Unspecified chemical cleaners may damage the LED package. If cleaning is necessary post-soldering, immerse the LEDs in ethyl alcohol or isopropyl alcohol at room temperature for no more than one minute.

6.2 Recommended PCB Pad Layout

A suggested land pattern (footprint) for the printed circuit board is provided to ensure proper solder joint formation, mechanical stability, and heat dissipation during reflow. Adherence to this layout promotes reliable assembly.

6.3 Tape and Reel Packaging

The LEDs are supplied in embossed carrier tape (8mm width) wound onto 7-inch (178mm) diameter reels. This packaging is compliant with EIA-481 standards for automated handling.

• Reel capacity: 2000 pieces per reel.
• Minimum order quantity for remnants: 500 pieces.
• The tape is sealed with a cover tape to protect components.
• A maximum of two consecutive empty pockets is allowed.

7. Cautions and Handling Instructions

7.1 Application Scope

These LEDs are designed for standard commercial and industrial electronic equipment. They are not intended for safety-critical applications where failure could lead to direct risk to life or health (e.g., aviation, medical life-support, transportation control) without prior consultation and specific qualification.

7.2 Storage Conditions

• Sealed Moisture Barrier Bag (MBB): Store at ≤ 30°C and ≤ 90% Relative Humidity (RH). Shelf life within the sealed bag with desiccant is one year.
• After Bag Opening: The storage environment should not exceed 30°C / 60% RH. Components removed from the MBB should be subjected to IR reflow soldering within one week (Moisture Sensitivity Level 3, MSL 3). For longer storage outside the original bag, store in a sealed container with desiccant or in a nitrogen desiccator. Components stored for more than one week outside the MBB require baking at approximately 60°C for at least 20 hours before soldering to prevent "popcorn" delamination during reflow.

7.3 Soldering Recommendations

This device is compatible with infrared reflow soldering processes. A lead-free (Pb-free) process profile is recommended.

• Reflow Soldering:
  • Pre-heat Temperature: 150°C – 200°C
  • Pre-heat Time: Maximum 120 seconds
  • Peak Body Temperature: Maximum 260°C
  • Time above 260°C: Maximum 10 seconds
  • Maximum number of reflow cycles: Two
• Hand Soldering (Iron):
  • Iron Tip Temperature: Maximum 300°C
  • Contact Time: Maximum 3 seconds per joint
  • Maximum number of hand-solder cycles: One

Note: The optimal reflow profile depends on the specific PCB design, solder paste, and oven. The provided conditions are guidelines based on JEDEC standards. Characterization for the specific assembly line is advised.

8. Design Considerations and Application Notes

8.1 Current Driving

Always drive LEDs with a constant current source or through a series current-limiting resistor. Operating at or below the maximum continuous forward current (25mA) is essential for longevity. The forward voltage varies with bin (1.8V to 2.4V), so the current-limiting circuit must be designed for the maximum V_F in the selected bin to ensure proper current under all conditions.

8.2 Thermal Management

While the power dissipation is relatively low (62.5mW), effective thermal management on the PCB is still important, especially in high ambient temperature environments or when multiple LEDs are placed closely. The PCB pad layout acts as a heat sink. Ensuring adequate copper area connected to the thermal pads helps maintain lower junction temperature, preserving luminous output and operational life.

8.3 Optical Design

The 25-degree viewing angle provides a relatively focused beam. For applications requiring wider illumination, secondary optics (e.g., diffusers, light guides) must be considered. The water-clear lens is suitable for applications where the chip color is not an issue when the LED is off.

9. Technical Principle: AlInGaP Technology

This LED uses an Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material grown on a substrate. By adjusting the ratios of these elements in the active region, the bandgap energy is tuned to emit light in the green-yellow-orange-red spectrum. AlInGaP technology is known for its high internal quantum efficiency and excellent performance at elevated temperatures compared to older technologies like GaAsP, resulting in higher brightness and better color stability.

10. Comparison and Selection Guidance

When selecting an SMD LED, key differentiating factors include:

• Chip Technology: AlInGaP (as used here) vs. InGaN (common for blue/white/green). AlInGaP typically offers higher efficiency in the amber-red range, while specific green AlInGaP devices provide distinct color points.
• Brightness (Luminous Intensity): The binning system (T, U, V) allows selection based on required brightness, impacting power consumption and visibility.
• Color Consistency (Wavelength Binning): The tight hue binning (B through E) is critical for applications where color matching between multiple LEDs is essential.
• Viewing Angle: A 25-degree angle is moderately focused. Wider or narrower angles are available in other packages for different diffusion requirements.
• Package Size and Thermal Performance: The compact SMD package saves board space but requires attention to PCB thermal design for maximum performance.

11. Frequently Asked Questions (FAQs)

11.1 What is the difference between Peak Wavelength and Dominant Wavelength?

Peak wavelength (λ_P) is the single wavelength at which the emitted optical power is maximum. Dominant wavelength (λ_d) is the single wavelength of monochromatic light that matches the perceived color of the LED when compared to a reference white light. λ_d is more relevant for color specification in human-centric applications.

11.2 Can I drive this LED with a 3.3V supply without a resistor?

No. The forward voltage is only 1.8-2.4V. Connecting it directly to a 3.3V supply would cause excessive current to flow, potentially exceeding the absolute maximum rating and destroying the LED instantly. A series current-limiting resistor is mandatory when using a voltage source.

11.3 How do I interpret the bin code (e.g., LTST-C950KGKT)?

The full part number includes internal coding. For procurement, the key selectable parameters are the Forward Voltage (D2/D3/D4), Luminous Intensity (T/U/V), and Dominant Wavelength (B/C/D/E) bins. These should be specified based on your design's electrical and optical requirements.

11.4 Why is baking required if the bag is opened for more than a week?

SMD packages can absorb moisture from the atmosphere. During the high-temperature reflow soldering process, this trapped moisture can rapidly vaporize, creating internal pressure that may crack the package or delaminate internal layers ("popcorn effect"). Baking removes this absorbed moisture.