LTST-S115KFKGKT-5A Dual Color SMD LED Datasheet - Side View Package - Orange/Green - 5mA - English Technical Document

1. Product Overview

The LTST-S115KFKGKT-5A is a dual-color, side-viewing Surface Mount Device (SMD) LED specifically engineered for applications requiring compact backlighting solutions, such as in LCD panels. This component integrates two distinct semiconductor chips within a single package: one emitting in the orange spectrum and the other in the green spectrum. Its primary design purpose is to provide a reliable, bright, and space-efficient light source compatible with modern automated assembly processes.

The core advantages of this LED include its compliance with RoHS (Restriction of Hazardous Substances) directives, classifying it as a green product. It utilizes ultra-bright AlInGaP (Aluminum Indium Gallium Phosphide) chip technology for both colors, which is known for high efficiency and good color purity. The device is packaged on 8mm tape wound onto 7-inch diameter reels, making it fully compatible with high-speed automatic pick-and-place equipment. Furthermore, it is designed to withstand standard infrared (IR) reflow soldering processes, facilitating its integration into printed circuit board (PCB) assemblies.

The target market encompasses consumer electronics, industrial instrumentation, and automotive interiors where side-emitting LEDs are crucial for edge-lit display backlighting, indicator panels, and status illumination in confined spaces.

2. Technical Parameter Deep Dive

2.1 Absolute Maximum Ratings

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

• Power Dissipation (Pd): 75 mW maximum per color chip.
• Peak Forward Current (I_FP): 80 mA, permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This rating is for transient events, not continuous operation.
• DC Forward Current (I_F): 30 mA maximum continuous current for reliable long-term operation.
• Reverse Voltage (V_R): 5 V maximum. Exceeding this voltage in reverse bias can damage the LED junction. Continuous operation under reverse voltage is prohibited.
• Operating Temperature Range: -30°C to +85°C. The device is functional within this ambient temperature span.
• Storage Temperature Range: -40°C to +85°C for non-operational conditions.
• Infrared Soldering Condition: The package can withstand a peak temperature of 260°C for a maximum of 10 seconds during reflow soldering, which is standard for lead-free (Pb-free) assembly processes.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at Ta=25°C and a forward current (I_F) of 5mA, which is a common test and operating condition.

• Luminous Intensity (I_V):
  • Orange Chip: Minimum 11.2 mcd, Typical value not specified, Maximum 71.0 mcd.
  • Green Chip: Minimum 4.5 mcd, Typical value not specified, Maximum 28.0 mcd.
  • Measurement is performed using a sensor-filter combination that approximates the photopic (CIE) eye-response curve.
• Viewing Angle (2θ_1/2): 130 degrees typical for both colors. This is the full angle at which the luminous intensity drops to half of its peak (axial) value, defining the beam width.
• Peak Emission Wavelength (λ_P): The wavelength at which the spectral power output is highest.
  • Orange: 611 nm typical.
  • Green: 574 nm typical.
• Dominant Wavelength (λ_d): The single wavelength perceived by the human eye that defines the color.
  • Orange: 605 nm typical at I_F=5mA.
  • Green: 571 nm typical at I_F=5mA.
• Spectral Line Half-Width (Δλ): The bandwidth of the emitted spectrum at half its maximum intensity.
  • Orange: 17 nm typical.
  • Green: 15 nm typical.
• Forward Voltage (V_F):
  • Both Colors: Typical 1.90 V, Maximum 2.30 V at I_F=5mA.
• Reverse Current (I_R): Maximum 10 µA when a reverse voltage (V_R) of 5V is applied.

3. Binning System Explanation

To ensure color and brightness consistency in production, LEDs are sorted into bins based on measured parameters.

3.1 Luminous Intensity Binning

Orange Color (@5mA):
Bin Code L: 11.2 - 18.0 mcd
Bin Code M: 18.0 - 28.0 mcd
Bin Code N: 28.0 - 45.0 mcd
Bin Code P: 45.0 - 71.0 mcd
Tolerance within each bin is ±15%.

Green Color (@5mA):
Bin Code J: 4.5 - 7.1 mcd
Bin Code K: 7.1 - 11.2 mcd
Bin Code L: 11.2 - 18.0 mcd
Bin Code M: 18.0 - 28.0 mcd
Tolerance within each bin is ±15%.

3.2 Dominant Wavelength Binning (Green Only)

Bin Code B: 564.5 - 567.5 nm
Bin Code C: 567.5 - 570.5 nm
Bin Code D: 570.5 - 573.5 nm
Tolerance for each wavelength bin is ±1 nm. Note: Orange wavelength binning is not specified in this datasheet.

4. Performance Curve Analysis

The datasheet references typical characteristic curves which are essential for design engineers. While the specific graphs are not reproduced in text, their implications are analyzed.

• Relative Luminous Intensity vs. Forward Current: This curve would show how light output increases with current, typically in a sub-linear fashion, highlighting the importance of current regulation over voltage driving for consistent brightness.
• Forward Voltage vs. Forward Current: This IV curve demonstrates the diode's exponential relationship, crucial for calculating series resistor values or designing constant-current drivers.
• Relative Luminous Intensity vs. Ambient Temperature: LED light output generally decreases as junction temperature rises. This curve is vital for thermal management in the application to maintain desired brightness levels.
• Spectral Distribution: Graphs showing the relative power versus wavelength for both orange and green chips, illustrating the peak and dominant wavelengths and the spectral half-width.

5. Mechanical & Package Information

5.1 Package Dimensions and Pin Assignment

The device conforms to an EIA standard side-view SMD package. Detailed dimensional drawings are provided in the original datasheet with all measurements in millimeters. Key mechanical notes include a general tolerance of ±0.10 mm unless otherwise specified.

Pin Assignment:
- Cathode 1 (C1): Connected to the Green chip.
- Cathode 2 (C2): Connected to the Orange chip.
The lens material is water clear.

5.2 Suggested Soldering Pad Layout & Polarity

A recommended solder pad footprint is provided to ensure proper mechanical attachment and solder joint reliability during reflow. A suggested soldering direction is also indicated to minimize potential tombstoning (component standing up on one end) during the reflow process. Designers should adhere to these guidelines for optimal assembly yield.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profile

A suggested infrared (IR) reflow profile is provided for lead-free (Pb-free) solder processes. Key parameters include:
- Pre-heat: 150°C to 200°C.
- Pre-heat Time: Maximum 120 seconds.
- Peak Temperature: Maximum 260°C.
- Time Above Liquidus: The sample profile shows critical time-temperature zones, including a recommended ramp-up rate, soak zone, and cooling rate, compliant with JEDEC standards. The profile on page 3 of the datasheet serves as a generic target, but board-specific characterization is advised.

6.2 Hand Soldering

If hand soldering is necessary:
- Iron Temperature: Maximum 300°C.
- Soldering Time: Maximum 3 seconds per joint.
- This should be performed only once to avoid thermal stress.

6.3 Cleaning

Only specified cleaning agents should be used. Unspecified chemicals may damage the LED package. If cleaning is required post-soldering, immersion in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute is recommended.

6.4 Storage Conditions

Sealed Package (with desiccant): Store at ≤30°C and ≤90% Relative Humidity (RH). Use within one year.
Opened Package: Store at ≤30°C and ≤60% RH. For components out of their original packaging for more than one week, a bake-out at approximately 60°C for at least 20 hours is recommended before soldering to remove moisture and prevent \"popcorning\" during reflow.

7. Packaging & Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied in embossed carrier tape:
- Tape Width: 8 mm.
- Reel Diameter: 7 inches.
- Quantity per Reel: 3000 pieces.
- Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
- Empty pockets in the tape are sealed with a top cover tape. The packaging conforms to ANSI/EIA 481-1-A-1994 standards. A maximum of two consecutive missing components is allowed per specification.

8. Application Recommendations

8.1 Typical Application Scenarios

• LCD Backlighting: Primary application as a side-view light source for small to medium LCD displays in consumer electronics, automotive dashboards, and industrial control panels.
• Status Indicators: Dual-color capability allows for multiple status signals (e.g., green for \"on/ready,\" orange for \"standby/warning\") from a single component footprint.
• Front Panel Illumination: Lighting for buttons, switches, or symbols where side emission is required.

8.2 Design Considerations

• Current Driving: Always use a series current-limiting resistor or a constant-current driver circuit. Calculate the resistor value using R = (V_supply - V_F) / I_F, using the maximum V_F from the datasheet for a safe design.
• Thermal Management: Although power dissipation is low, ensure adequate PCB copper area or thermal vias if operating at high ambient temperatures or near maximum current to maintain light output and longevity.
• ESD Protection: Standard ESD precautions should be observed during handling and assembly, as with all semiconductor devices.
• Optical Design: The 130-degree viewing angle should be considered for light guide or diffuser design in backlight applications to achieve uniform illumination.

9. Technical Comparison & Differentiation

While a direct competitor comparison is not provided, the key differentiating features of this component can be inferred:
1. Dual-Chip in Single Package: Saves PCB space and assembly cost compared to using two separate single-color LEDs.
2. Side-View Form Factor: Essential for specific backlighting and edge-lit applications where top-emitting LEDs are unsuitable.
3. AlInGaP Technology: Offers higher efficiency and better temperature stability for orange and red colors compared to older technologies like GaAsP.
4. Reflow Compatibility: Designed for modern SMT assembly lines, unlike older through-hole LEDs requiring manual soldering.

10. Frequently Asked Questions (FAQ)

Q1: Can I drive both LED chips simultaneously at their maximum DC current (30mA each)?
A: No. The absolute maximum power dissipation is 75 mW per chip. At 30mA and a typical V_F of 1.9V, power dissipation would be 57mW, which is within limits. However, driving both at 30mA simultaneously would require careful thermal consideration of the total heat generated in the tiny package. It is generally advisable to operate below absolute maximum ratings for reliability.

Q2: What is the difference between Peak Wavelength and Dominant Wavelength?
A: Peak Wavelength (λ_P) is the physical point of highest spectral output. Dominant Wavelength (λ_d) is a calculated value based on human color perception (CIE chart) and is the single wavelength that best describes the perceived color. They are often close but not identical, especially for broader spectra.

Q3: How do I interpret the bin codes when ordering?
A: Specify the desired bin codes for luminous intensity (for both orange and green) and for dominant wavelength (for green). For example, ordering \"Orange Bin P, Green Bin M, Wavelength Bin D\" would get you the brightest orange, a bright green, and a green towards the longer wavelength side of its range. This ensures color and brightness matching in your production.

11. Practical Design Case Study

Scenario: Designing a status indicator for a portable device with a single 3.3V supply. The indicator must show green for \"power on\" and orange for \"charging.\" Space is extremely limited.

Solution: Use the LTST-S115KFKGKT-5A. Design a driver circuit with two GPIO pins from a microcontroller.
- Connect GPIO1 to the Green cathode (C1) via a current-limiting resistor.
- Connect GPIO2 to the Orange cathode (C2) via another resistor.
- The common anodes are connected to the 3.3V rail.
Calculate the resistor value for a target I_F of 5mA (a common value for good visibility at low power): R = (3.3V - 1.9V) / 0.005A = 280 Ohms. Use the next standard value, 270 or 300 Ohms. The microcontroller can sink current by pulling the GPIO pin low to turn on the respective LED. This design uses one component footprint for two colors, saving space and simplifying assembly.

12. Technology Principle Introduction

The LED is based on AlInGaP semiconductor material. When a forward voltage is applied across the p-n junction, electrons and holes recombine, releasing energy in the form of photons (light). The specific color (wavelength) of the emitted light is determined by the bandgap energy of the semiconductor material. AlInGaP allows for the tuning of this bandgap to produce colors in the red, orange, amber, and yellow-green spectrum with high efficiency. The side-view package incorporates a molded plastic lens that shapes the light output, providing the wide 130-degree viewing angle suitable for backlight applications.

13. Industry Trends & Developments

The trend in SMD LEDs for backlighting and indicators continues towards:
1. Higher Efficiency (lm/W): Reducing power consumption for battery-operated devices and meeting energy regulations.
2. Improved Color Consistency & Binning: Tighter binning tolerances to ensure uniform appearance in displays without additional calibration.
3. Miniaturization: Even smaller package sizes (e.g., 0402, 0201 metric) for increasingly compact electronics.
4. Higher Reliability & Lifetime: Improved materials and packaging to withstand harsher environmental conditions, especially in automotive and industrial applications.
5. Integrated Solutions: Moving beyond simple discrete LEDs towards modules with integrated drivers, controllers, and light guides.