LTST-S115TGKFKT Dual Color SMD LED Datasheet - Side View Package - Green (530nm) & Orange (611nm) - 3.2V/2.0V - 76mW/75mW - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a dual-color, side-view surface-mount device (SMD) LED. This component is specifically engineered for applications requiring compact, high-brightness illumination from the side, with a primary target market being LCD panel backlighting units. Its core advantages include the integration of two distinct semiconductor chips within a single package, compatibility with automated assembly processes, and adherence to RoHS and green product standards.

The LED features a water-clear lens and houses two separate light-emitting chips: one producing green light and the other producing orange light. This design allows for color mixing or independent control in space-constrained designs. The package is supplied on industry-standard 8mm tape mounted on 7-inch reels, facilitating high-volume, automated pick-and-place assembly and reflow soldering.

2. Technical Parameters Deep Objective 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. Key parameters include:

• Power Dissipation (Pd): 76 mW for the green chip, 75 mW for the orange chip. This is the maximum allowable power the LED can dissipate as heat at an ambient temperature (Ta) of 25°C. Exceeding this limit risks thermal runaway and failure.
• Peak Forward Current (I_FP): 100 mA (green) and 80 mA (orange) under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This rating is significantly higher than the DC rating, allowing for brief high-current pulses for applications like multiplexing or achieving momentary peak brightness.
• DC Forward Current (I_F): 20 mA (green) and 30 mA (orange). This is the recommended continuous operating current for reliable long-term performance.
• Reverse Voltage (V_R): 5 V for both chips. Applying a reverse voltage exceeding this value can cause immediate and catastrophic junction breakdown. The datasheet explicitly notes that reverse voltage operation cannot be continuous.
• Temperature Ranges: Operating from -20°C to +80°C; storage from -30°C to +100°C. These define the environmental limits for functional use and non-operational storage.
• Infrared Soldering Condition: Withstands 260°C for 10 seconds, which is a standard requirement for lead-free (Pb-free) reflow soldering processes per IPC/JEDEC standards.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at Ta=25°C and I_F=20mA, representing the expected behavior under normal operating conditions.

• Luminous Intensity (I_V): The green chip has a minimum of 71.0 mcd and a maximum of 450.0 mcd. The orange chip has a minimum of 28.0 mcd and a maximum of 280.0 mcd. The wide range is managed through a binning system (detailed later). Intensity is measured using a sensor filtered to match the photopic (CIE) human eye response curve.
• Viewing Angle (2θ_1/2): A typical value of 130 degrees for both colors. This wide viewing angle is characteristic of side-view LEDs and is ideal for backlighting applications where even light distribution across a panel is required.
• Peak Wavelength (λ_P): Typically 530 nm for green and 611 nm for orange. This is the wavelength at which the spectral power distribution is maximum.
• Dominant Wavelength (λ_d): Typically 525 nm for green and 605 nm for orange. This is the single wavelength perceived by the human eye that defines the color, derived from the CIE chromaticity diagram. It is the more relevant parameter for color specification.
• Spectral Line Half-Width (Δλ): Typically 35 nm for green and 17 nm for orange. This indicates the spectral purity; a narrower half-width means a more saturated, pure color. The orange AlInGaP chip exhibits higher color purity than the green InGaN chip in this device.
• Forward Voltage (V_F): Typically 3.2 V (max 3.6 V) for green and 2.0 V (max 2.4 V) for orange at 20mA. This parameter is crucial for driver circuit design, as the two chips require different supply voltages for the same current.
• Reverse Current (I_R): Maximum 10 µA for both at V_R=5V. A low reverse leakage current is indicative of a high-quality semiconductor junction.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins. This system allows designers to select parts that meet specific minimum criteria for their application.

3.1 Luminous Intensity Binning

The luminous output is categorized into bins denoted by letters. Each bin has a defined minimum and maximum intensity, with a tolerance of +/-15% within each bin.

• Green Chip: Bins Q (71.0-112.0 mcd), R (112.0-180.0 mcd), S (180.0-280.0 mcd), T (280.0-450.0 mcd).
• Orange Chip: Bins N (28.0-45.0 mcd), P (45.0-71.0 mcd), Q (71.0-112.0 mcd), R (112.0-180.0 mcd), S (180.0-280.0 mcd).

3.2 Dominant Wavelength Binning (Green Only)

The green chips are also binned by dominant wavelength to control color consistency.

• Bins AP (520.0-525.0 nm), AQ (525.0-530.0 nm), AR (530.0-535.0 nm). The tolerance for each wavelength bin is +/- 1 nm.

Specific bin combinations for the complete part (e.g., intensity bin for green, intensity bin for orange, wavelength bin for green) would typically be specified in a full ordering code or available from the manufacturer.

4. Performance Curve Analysis

The datasheet references typical characteristic curves which are essential for understanding device behavior under varying conditions. While the exact graphs are not provided in the text, their standard interpretations are:

• I-V (Current-Voltage) Curve: Shows the relationship between forward voltage (V_F) and forward current (I_F). It is non-linear, with a turn-on/threshold voltage (approx. 2.8V for green, 1.8V for orange) after which current increases rapidly. This curve is vital for designing constant-current drivers.
• Relative Luminous Intensity vs. Forward Current: Demonstrates how light output increases with current, typically in a near-linear relationship within the recommended operating range. Driving above I_F yields diminishing returns and increases heat.
• Relative Luminous Intensity vs. Ambient Temperature: Shows the derating of light output as junction temperature rises. LEDs are less efficient at higher temperatures. This curve is critical for thermal management design to maintain consistent brightness.
• Spectral Distribution: A plot of relative radiant power versus wavelength, showing the peak (λ_P) and the half-width (Δλ).

5. Mechanical & Packaging Information

5.1 Package Dimensions and Polarity

The device uses a standard EIA package footprint. The pin assignment is clearly defined: Cathode 2 (C2) is for the Green (InGaN) chip, and Cathode 1 (C1) is for the Orange (AlInGaP) chip. The common anode configuration is typical for multi-chip LEDs. Detailed dimensioned drawings (not fully detailed in the text extract) would provide exact length, width, height, lead spacing, and lens geometry, all with a standard tolerance of ±0.10 mm.

5.2 Suggested Soldering Pad Layout and Direction

The datasheet includes recommendations for the printed circuit board (PCB) land pattern (solder pad dimensions) and the orientation for soldering. Following these guidelines ensures proper mechanical alignment, reliable solder joint formation, and prevents issues like tombstoning during reflow.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profile

A suggested infrared (IR) reflow profile for lead-free processes is provided. Key parameters of this profile, which aligns with JEDEC standards, include:

• Pre-heat: 150-200°C for a maximum of 120 seconds to gradually heat the board and components, activating the flux and minimizing thermal shock.
• Peak Temperature: Maximum of 260°C. The device is rated to withstand this temperature for 10 seconds.
• The profile emphasizes that board-specific characterization is necessary due to variations in board design, components, and solder paste.

6.2 Hand Soldering

If manual soldering is necessary, a soldering iron temperature not exceeding 300°C is recommended, with a soldering time of 3 seconds maximum per joint. This should be performed only once to avoid thermal damage to the plastic package and the wire bonds inside.

6.3 Cleaning

Only specified cleaning agents should be used. The recommended method is immersion in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute. Harsh or unspecified chemicals can damage the epoxy lens and package, leading to reduced light output or premature failure.

6.4 Storage and Handling

LEDs are moisture-sensitive devices (MSD).

• Sealed Package: Store at ≤30°C and ≤90% RH. The shelf life in the moisture-proof bag with desiccant is one year.
• Opened Package: Storage conditions should not exceed 30°C and 60% RH. Components removed from their original packaging should be reflow-soldered within one week. For longer storage, they must be kept in a sealed container with desiccant or in a nitrogen desiccator. If stored open for more than one week, a bake-out at approximately 60°C for at least 20 hours is required before assembly to remove absorbed moisture and prevent "popcorning" during reflow.

7. Packaging & Ordering Information

The product is supplied in a tape-and-reel format compatible with automated SMD assembly equipment.

• Reel: 7-inch diameter reel.
• Tape: 8mm wide carrier tape.
• Quantity: 3000 pieces per full reel. A minimum packing quantity of 500 pieces is available for remainder quantities.
• Quality: The packaging conforms to ANSI/EIA 481-1-A-1994 specifications. Empty pockets in the tape are sealed with a cover tape. The maximum number of consecutive missing components ("missing lamps") is two.

8. Application Suggestions

8.1 Typical Application Scenarios

The primary and explicitly stated application is LCD Backlighting, particularly for small to medium-sized displays where side-view LEDs are used to inject light into a light guide plate (LGP). The dual-color capability allows for tunable white backlights (by mixing green and orange with a blue LED elsewhere) or for creating specific color accents and indicators within the display assembly. Other potential applications include status indicators, panel illumination, and decorative lighting in consumer electronics, office equipment, and communication devices.

8.2 Design Considerations

• Driver Circuit: Since the green and orange chips have different forward voltages (3.2V vs 2.0V), they cannot be driven in a simple parallel configuration from a single constant-voltage source without current-limiting resistors for each chip. A constant-current driver is recommended for optimal performance and stability.
• Thermal Management: Although power dissipation is low, proper PCB layout with adequate thermal relief and possibly a small copper pad can help dissipate heat, especially if operating near maximum current or in elevated ambient temperatures. This maintains luminous efficiency and longevity.
• Optical Design: The 130-degree viewing angle is suitable for edge-lit backlights. The design of the light guide plate, diffusers, and reflectors must be optimized to couple with this LED's emission pattern for uniform illumination.

9. Technical Comparison & Differentiation

This device offers specific advantages in its niche:

• Dual-Chip Integration: Compared to using two separate single-color LEDs, this package saves PCB space, simplifies assembly (one placement step), and ensures precise mechanical alignment between the two light sources, which is critical for color mixing.
• Side-View Form Factor: Versus top-view LEDs, the side-view package is essential for slim backlighting modules where height (Z-axis) is constrained, and light must be emitted parallel to the PCB plane.
• Chip Technology: The use of AlInGaP for orange offers higher efficiency and better temperature stability compared to older technologies like GaAsP, resulting in brighter and more consistent orange light output.
• Process Compatibility: Full compatibility with reflow soldering and automatic placement makes it suitable for modern, high-volume manufacturing lines.

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive both the green and orange chips simultaneously at their maximum DC current (20mA and 30mA)?

A1: Yes, but you must consider the total power dissipation. Simultaneous operation at max current would dissipate power roughly equal to (3.2V * 0.02A) + (2.0V * 0.03A) = 0.124W. This is below the individual Pd ratings but close to their sum. Adequate thermal design on the PCB is necessary to prevent the junction temperature from exceeding safe limits, especially in a sealed enclosure.

Q2: Why is the reverse voltage rating only 5V, and what does "cannot be continued operating" mean?

A2: LED semiconductor junctions are not designed to block high reverse voltages. A 5V rating is typical. The phrase means that even applying a reverse voltage below 5V continuously is not recommended or specified. In circuit design, ensure the LED is never subjected to a reverse bias, or use a protection diode in parallel if necessary.

Q3: How do I interpret the bin codes when ordering?

A3: You would specify the required bin codes for luminous intensity (for both green and orange) and for the dominant wavelength (for green) to ensure your product receives LEDs with the desired brightness and color characteristics. For example, you might order parts binned as "Green: Intensity T, Wavelength AQ; Orange: Intensity R". Consult the manufacturer for the exact ordering code format.

11. Practical Design Case

Scenario: Designing a status indicator for a device that requires two distinct colors (green for "Ready," orange for "Standby/Warning") in an extremely space-constrained area on the edge of a PCB that is mounted vertically inside a product chassis.

Implementation: The LTST-S115TGKFKT is an ideal choice. A single component footprint is used. A simple microcontroller GPIO pin can be connected to each cathode (C1 for orange, C2 for green) via a suitable current-limiting resistor (calculated based on the desired current, up to 20/30mA, and the supply voltage), with the common anode connected to the positive supply. The side-view emission allows the light to be directed out through a small aperture or light pipe on the side of the device enclosure. The wide viewing angle ensures the indicator is visible from a broad range of perspectives. The reflow-compatible package allows it to be soldered alongside all other SMD components in one pass.

12. Principle Introduction

Light emission in LEDs is based on electroluminescence in a semiconductor p-n junction. When a forward voltage is applied, electrons and holes are injected into the active region where they recombine, releasing energy in the form of photons. The color (wavelength) of the emitted light is determined by the bandgap energy of the semiconductor material.

• Green Chip (InGaN): Indium Gallium Nitride is a compound semiconductor whose bandgap can be tuned by adjusting the indium/gallium ratio to emit in the blue to green spectrum. Here, it is engineered for green emission at ~530 nm.
• Orange Chip (AlInGaP): Aluminum Indium Gallium Phosphide is another compound semiconductor known for high efficiency in the red, orange, and yellow wavelength regions. Its bandgap is tuned here for orange emission at ~611 nm.

The two chips are mounted on a lead frame within a single epoxy package with a water-clear lens that minimally absorbs the emitted light, allowing for high optical efficiency.

13. Development Trends

The field of SMD LEDs continues to evolve with several clear trends relevant to components like this one:

• Increased Efficiency (lm/W): Ongoing material science and chip design improvements aim to extract more light (lumens) from the same electrical input power (watts), reducing energy consumption and thermal load.
• Higher Reliability and Lifetime: Advancements in packaging materials, die attach techniques, and phosphor technology (where applicable) are extending operational lifetimes and improving performance under harsh environmental conditions.
• Miniaturization: The drive for smaller electronic devices pushes for LEDs in even smaller package footprints and lower profiles while maintaining or increasing light output.
• Color Precision and Consistency: Tighter binning tolerances and improved manufacturing processes lead to less variation in color and brightness between batches, which is critical for applications requiring uniform appearance.
• Integration: Beyond dual-color, there is a trend towards integrating more functions, such as RGB chips, driver ICs, or even photodetectors, into single packages to create smarter, more compact lighting solutions.