SMD LED LTST-S115KGKFKT-5A Datasheet - Side Looking Dual Color (Green/Orange) - 5mA - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTST-S115KGKFKT-5A, a side-looking, dual-color Surface-Mount Device (SMD) Light Emitting Diode (LED). This component integrates two distinct semiconductor chips within a single package: one emitting green light and the other emitting orange light. It is designed for applications requiring compact, reliable, and bright indicator lights or backlighting where space is at a premium and multiple color states are needed from a single component location.

The LED utilizes advanced Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor technology for both chips, which is known for producing high luminous efficiency and excellent color purity. The device is housed in a standard EIA-compliant package, making it compatible with automated pick-and-place assembly equipment and standard infrared (IR) reflow soldering processes used in high-volume electronics manufacturing. The product is compliant with RoHS (Restriction of Hazardous Substances) directives, classifying it as a green product.

2. Absolute Maximum Ratings

The absolute maximum ratings define the stress limits beyond which permanent damage to the device may occur. These ratings are specified at an ambient temperature (Ta) of 25°C and are identical for both the green and orange chips within the package.

• Power Dissipation (Pd): 75 mW maximum per chip. Exceeding this limit can lead to overheating and catastrophic failure.
• Peak Forward Current (I_FP): 80 mA maximum. This rating applies under pulsed conditions with a duty cycle of 1/10 and a pulse width of 0.1 ms. It should not be used for continuous DC operation.
• DC Forward Current (I_F): 30 mA maximum for continuous operation. This is the recommended maximum current for reliable long-term performance.
• Operating Temperature Range: -30°C to +85°C. The device is designed to function within this ambient temperature range.
• Storage Temperature Range: -40°C to +85°C. The device can be stored without degradation within these limits.
• Infrared Soldering Condition: The package can withstand a peak temperature of 260°C for a maximum of 10 seconds during reflow soldering, which is typical for lead-free (Pb-free) assembly processes.

3. Electrical and Optical Characteristics

The following parameters are measured at Ta=25°C with a forward current (I_F) of 5 mA, unless otherwise stated. These represent the typical performance of the device.

3.1 Luminous Intensity and Viewing Angle

• Green Chip Luminous Intensity (I_V): Minimum 9.0 mcd, typical value not specified, maximum 22.4 mcd.
• Orange Chip Luminous Intensity (I_V): Minimum 11.2 mcd, typical value not specified, maximum 28.0 mcd.
• Viewing Angle (2θ_1/2): 120 degrees (typical) for both colors. The viewing angle is defined as the full angle at which the luminous intensity is half of the intensity measured on the central axis (0°). This wide viewing angle is characteristic of side-looking LED packages.

3.2 Spectral Characteristics

• Green Chip Peak Wavelength (λ_P): 575 nm (typical).
• Orange Chip Peak Wavelength (λ_P): 611 nm (typical).
• Green Chip Dominant Wavelength (λ_d): Ranges from 567.5 nm (min) to 576.5 nm (max) at I_F=5mA. The dominant wavelength is the single wavelength perceived by the human eye that defines the color.
• Orange Chip Dominant Wavelength (λ_d): Ranges from 600.5 nm (min) to 612.5 nm (max) at I_F=5mA.
• Spectral Line Half-Width (Δλ): Approximately 20 nm (typical) for green and 17 nm (typical) for orange. This parameter indicates the spectral purity of the emitted light.

3.3 Electrical Parameters

• Forward Voltage (V_F): For both green and orange chips, V_F ranges from 1.7 V (minimum) to 2.4 V (maximum) at I_F=5mA.
• Reverse Current (I_R): 10 μA maximum for both chips when a reverse voltage (V_R) of 5V is applied. Important Note: This LED is not designed for operation under reverse bias. The I_R test is for characterization only; applying reverse voltage in circuit may damage the device.

4. Binning System Explanation

To ensure consistency in brightness and color, the LEDs are sorted into bins based on measured luminous intensity and dominant wavelength. This allows designers to select parts that meet specific application requirements for uniformity.

4.1 Luminous Intensity Binning

Green Chip: Binned at I_F=5mA.
- Bin Code KL: 9.0 mcd (Min) to 14.0 mcd (Max).
- Bin Code LM: 14.0 mcd (Min) to 22.4 mcd (Max).
Tolerance within each intensity bin is +/-15%.

Orange Chip: Binned at I_F=5mA.
- Bin Code L: 11.2 mcd (Min) to 18.0 mcd (Max).
- Bin Code M: 18.0 mcd (Min) to 28.0 mcd (Max).
Tolerance within each intensity bin is +/-15%.

4.2 Dominant Wavelength Binning

Green Chip: Binned at I_F=5mA.
- Bin Code C: 567.5 nm to 570.5 nm.
- Bin Code D: 570.5 nm to 573.5 nm.
- Bin Code E: 573.5 nm to 576.5 nm.
Tolerance for each wavelength bin is +/- 1 nm.

Orange Chip: Binned at I_F=5mA.
- Bin Code P: 600.5 nm to 603.5 nm.
- Bin Code Q: 603.5 nm to 606.5 nm.
- Bin Code R: 606.5 nm to 609.5 nm.
- Bin Code S: 609.5 nm to 612.5 nm.
Tolerance for each wavelength bin is +/- 1 nm.

5. Performance Curve Analysis

The datasheet references typical performance curves which are essential for understanding device behavior under different conditions. While the specific graphs are not reproduced in text, their implications are critical for design.

• Forward Current vs. Forward Voltage (I-V Curve): This curve shows the relationship between the current flowing through the LED and the voltage drop across it. It is non-linear, typical of a diode. Designers use this to determine the appropriate current-limiting resistor value for a given supply voltage to achieve the desired operating current (e.g., 5mA or up to 30mA DC).
• Luminous Intensity vs. Forward Current: This graph illustrates how light output increases with current. It is generally linear within the recommended operating range but will saturate at very high currents. It helps in selecting the drive current for required brightness.
• Luminous Intensity vs. Ambient Temperature: The light output of LEDs decreases as the junction temperature rises. This curve is vital for applications operating in elevated temperature environments to ensure sufficient brightness is maintained.
• Spectral Distribution: These curves plot the relative radiant power against wavelength, showing the peak and dominant wavelengths and the spectral half-width, confirming the color purity.

6. Mechanical and Package Information

6.1 Package Dimensions and Pin Assignment

The device uses a standard EIA package footprint. The specific dimensional drawing provides critical measurements for PCB (Printed Circuit Board) land pattern design. The pin assignment is as follows: Cathode for the Orange chip is connected to Pin C1, and the Cathode for the Green chip is connected to Pin C2. The common anode is typically the other pin(s) as defined in the drawing. Correct polarity must be observed during assembly.

6.2 Suggested Soldering Pad Layout

A recommended solder pad footprint is provided to ensure reliable solder joint formation during reflow. Adhering to these dimensions helps prevent tombstoning (component standing up on one end) and ensures proper wetting and mechanical strength.

7. Soldering and Assembly Guidelines

7.1 Reflow Soldering Profile

A detailed suggested IR reflow profile is provided for Pb-free assembly processes. Key parameters include:
- Pre-heat Zone: Ramp-up to 150-200°C.
- Soak/Pre-heat Time: Maximum of 120 seconds.
- Peak Temperature: Maximum of 260°C.
- Time Above Liquidus (TAL): The time within 5°C of the peak temperature should be limited, typically to a maximum of 10 seconds as per the absolute rating.
Critical Note: The datasheet explicitly states that soldering profiles with peak temperatures below 245°C may be insufficient unless the PCB has tin plating, highlighting the need for adequate thermal energy for proper solder joint formation with lead-free solder.

7.2 Hand Soldering

If hand soldering is necessary, it should be performed with a temperature-controlled iron.
- Iron Temperature: Maximum 300°C.
- Soldering Time: Maximum 3 seconds per joint.
- Frequency: This should be performed only once to avoid thermal stress damage to the LED package or wire bonds.

7.3 Cleaning

If cleaning is required after soldering, only specified solvents should be used. The datasheet recommends immersing the LED in ethyl alcohol or isopropyl alcohol at normal room temperature for less than one minute. The use of unspecified chemicals can damage the plastic lens or package material.

8. Packaging and Handling

8.1 Tape and Reel Specifications

The LEDs are supplied in industry-standard 8mm carrier tape on 7-inch (178mm) diameter reels. This packaging is compatible with automated SMD assembly equipment.
- Quantity per Reel: 3000 pieces.
- Minimum Pack Quantity: 500 pieces for remainder quantities.
- The packaging follows ANSI/EIA-481 specifications. Empty pockets in the tape are sealed with a cover tape.

8.2 Storage Conditions

Proper storage is crucial to maintain solderability and performance.
- Sealed Package: Store at ≤30°C and ≤90% Relative Humidity (RH). The components are usable for one year from the date code when stored in the original moisture-barrier bag with desiccant.
- Opened Package: If the moisture barrier bag is opened, the storage ambient should not exceed 30°C / 60% RH. Components should be subjected to IR reflow soldering within one week of exposure. For longer exposure, baking at approximately 60°C for at least 20 hours is recommended before assembly to remove absorbed moisture and prevent \"popcorning\" (package cracking during reflow).

8.3 Electrostatic Discharge (ESD) Precautions

AlInGaP LEDs are sensitive to electrostatic discharge. Handling precautions must be taken:
- Use grounded wrist straps or anti-static gloves.
- Ensure all workstations, tools, and equipment are properly grounded.
- Transport and store components in ESD-safe packaging.

9. Application Suggestions and Design Considerations

Typical Applications: This dual-color, side-emitting LED is ideal for space-constrained applications where status indication is required. Examples include:
- Panel-mounted status indicators on consumer electronics, networking equipment, or industrial controls.
- Backlighting for symbols or icons on front panels, where light needs to be directed parallel to the PCB.
- Multi-state indicators (e.g., green for \"on/ready,\" orange for \"standby/warning\") using a single component footprint.

Design Considerations:
1. Current Limiting: Always use a series resistor to limit the forward current to the desired value (e.g., 5mA for standard brightness, up to 30mA for maximum). Calculate the resistor value using R = (V_supply - V_F) / I_F, using the maximum V_F from the datasheet for a conservative design.
2. Thermal Management: While power dissipation is low, ensure the PCB layout does not trap heat around the LED, especially if driving near the maximum DC current. Adequate copper area can help dissipate heat.
3. Driving Circuit: The two chips have separate cathodes (C1, C2) and a common anode. They can be driven independently by connecting the common anode to a positive supply and sinking current through the respective cathode pins via transistors or microcontroller GPIO pins configured as current sinks.
4. Optical Design: The 120-degree side-emitting pattern is useful for wide-angle visibility. Consider the placement relative to light pipes or diffusers to achieve the desired visual effect.

10. Technical Comparison and Differentiation

The key differentiating features of this LED are its dual-color capability in a side-looking package and the use of AlInGaP technology.

• vs. Single-Color Side-Looking LEDs: This device saves PCB space and assembly cost by replacing two separate single-color LEDs with one component, simplifying the bill of materials and layout.
• AlInGaP vs. Other Technologies: Compared to traditional GaP (Gallium Phosphide) LEDs, AlInGaP offers significantly higher luminous efficiency, resulting in brighter output at the same drive current. It also provides superior color saturation and stability over temperature and lifetime compared to some older technologies.
• Package Compatibility: The standard EIA footprint ensures drop-in compatibility with many existing designs and automated assembly lines, reducing qualification effort.

11. Frequently Asked Questions (FAQ)

Q1: Can I drive both the green and orange chips simultaneously?
A1: Yes, but you must ensure the total power dissipation does not exceed the package limits. If driving both at their maximum DC current (30mA each) with a typical V_F of ~2.0V, the power would be ~120mW, exceeding the 75mW per chip rating. Therefore, simultaneous operation at full current is not recommended. For simultaneous use, derate the current to keep total power within safe limits.

Q2: What is the difference between peak wavelength and dominant wavelength?
A2: Peak wavelength (λ_P) is the wavelength at which the emission spectrum has its maximum intensity. Dominant wavelength (λ_d) is the single wavelength that the human eye perceives as the color of the light, calculated from the CIE chromaticity coordinates. λ_d is often more relevant for color specification in applications.

Q3: Why is the reverse current rating important if I shouldn't apply reverse voltage?
A3: The I_R rating is a quality and leakage test parameter for the manufacturer. In your circuit, you must protect the LED from accidental reverse voltage, which can occur during hot-plugging or in certain circuit configurations. Using a series diode or ensuring correct polarity is essential.

Q4: How do I interpret the bin codes when ordering?
A4: The part number LTST-S115KGKFKT-5A includes specific bin codes (e.g., KG for green intensity/wavelength, KF for orange). Consult the manufacturer's detailed bin code list or specify your required brightness (e.g., LM bin for brighter green) and color (e.g., D bin for specific green hue) when ordering to ensure you receive parts matching your uniformity requirements.

12. Operational Principles

Light emission in this LED is based on electroluminescence in AlInGaP semiconductor materials. When a forward voltage exceeding the diode's turn-on voltage (approximately 1.7-2.4V) is applied, electrons and holes are injected into the active region of the semiconductor chip from the n-type and p-type layers, respectively. These charge carriers recombine, releasing energy in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the bandgap energy of the AlInGaP alloy composition, which is carefully engineered during chip fabrication to produce green (~575 nm) and orange (~611 nm) light. The side-looking package incorporates a molded lens that shapes the emitted light into a wide 120-degree viewing pattern, directing it parallel to the mounting plane of the PCB.