LTST-S327KGKFKT Dual Color SMD LED Datasheet - Package Dimensions - Green/Orange - 30mA - 75mW - English Technical Document

1. Product Overview

The LTST-S327KGKFKT is a compact, surface-mount dual-color LED designed for automated printed circuit board assembly. It integrates two distinct light-emitting chips within a single EIA standard package, making it suitable for space-constrained applications requiring multiple status indications or backlighting in a minimal footprint.

1.1 Core Advantages

• Dual-Color Integration: Combines green and orange AlInGaP chips in one package, saving board space and simplifying assembly for multi-indicator designs.
• High Brightness: Utilizes ultra-bright AlInGaP semiconductor technology for excellent luminous intensity.
• Manufacturing Compatibility: Features tin-plated leads, is compatible with infrared reflow soldering processes, and is supplied on 8mm tape reels for automated pick-and-place equipment.
• Environmental Compliance: Meets RoHS (Restriction of Hazardous Substances) directives.

1.2 Target Applications

This component is ideal for a wide range of electronic devices where reliable, compact visual indicators are required. Primary application areas include:

• Telecommunication equipment (e.g., cellular phones, network switches)
• Office automation devices (e.g., notebooks, printers)
• Consumer appliances and industrial control panels
• Keypad or keyboard backlighting
• Status and power indicators
• Symbolic luminaries and micro-displays

2. In-Depth Technical Parameter Analysis

The following section provides a detailed breakdown of the LED's operational limits and performance characteristics under standard test conditions (Ta=25°C).

2.1 Absolute Maximum Ratings

These values represent the stress limits beyond which permanent damage to the device may occur. Continuous operation at these limits is not advised.

• Power Dissipation (P_d): 75 mW per color chip.
• Continuous Forward Current (I_F): 30 mA DC.
• Peak Forward Current: 80 mA (pulsed at 1/10 duty cycle, 0.1ms pulse width).
• Reverse Voltage (V_R): 5 V.
• Operating Temperature Range: -30°C to +85°C.
• Storage Temperature Range: -40°C to +85°C.
• Soldering Temperature: Withstands 260°C for 10 seconds (Pb-free process).

2.2 Electro-Optical Characteristics

Measured at I_F = 20mA, these parameters define the typical performance of the LED.

Notes on Measurement: Luminous intensity is measured using a sensor filtered to match the CIE photopic eye-response curve. The viewing angle (2θ_1/2) is the full angle at which intensity drops to half its on-axis value. Dominant wavelength is derived from CIE chromaticity coordinates.

2.3 Thermal Considerations

The maximum power dissipation of 75mW per chip is a critical design parameter. Exceeding this limit, either through high forward current or elevated ambient temperature, will reduce luminous output and shorten the device's operational lifespan. Proper PCB layout with adequate thermal relief is recommended for applications running at high duty cycles or in warm environments.

3. Binning System Explanation

To ensure consistency in production, LEDs are sorted into performance bins based on luminous intensity.

3.1 Luminous Intensity Binning

The luminous output of each color chip is classified into specific code ranges with a tolerance of ±15% within each bin.

• Green Chip Bins (mcd @20mA):
  • Code P: 45.0 to 71.0 mcd
  • Code Q: 71.0 to 112.0 mcd
• Orange Chip Bins (mcd @20mA):
  • Code N2: 36.0 to 45.0 mcd
  • Code P: 45.0 to 71.0 mcd
  • Code Q1: 71.0 to 90.0 mcd

This binning allows designers to select parts that meet specific brightness requirements for their application, ensuring visual consistency across a product line.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet, their implications are summarized here.

4.1 Current vs. Voltage (I-V) Curve

The forward voltage (V_F) exhibits a logarithmic relationship with forward current (I_F). For both green and orange chips, V_F typically ranges from 1.7V to 2.4V at the standard 20mA drive current. Designing with a current-limiting resistor is essential, as LEDs are current-driven devices; a small increase in voltage can cause a large, potentially damaging increase in current.

4.2 Luminous Intensity vs. Current (I_V-I_F)

Luminous intensity is approximately proportional to the forward current up to the maximum rated continuous current. However, efficiency (lumens per watt) may decrease at higher currents due to increased thermal effects.

4.3 Spectral Distribution

The green chip emits light centered around a peak wavelength (λ_P) of 574nm with a spectral half-width (Δλ) of 20nm. The orange chip emits at a peak of 611nm with a half-width of 17nm. The narrower spectrum of the orange chip indicates a more saturated color.

5. Mechanical and Package Information

5.1 Physical Dimensions

The device conforms to an industry-standard SMD package outline. Key dimensions include length, width, and height, all with a standard tolerance of ±0.1mm unless otherwise specified. The water-clear lens material allows for high light transmission for both colors.

5.2 Pad Layout and Polarity Identification

The component has two anodes (A1 for Green, A2 for Orange) and a common cathode. The datasheet provides a recommended PCB land pattern (pad geometry) to ensure proper solder joint formation during reflow and to provide adequate mechanical stability. Correct polarity orientation during placement is crucial for functionality.

6. Soldering and Assembly Guidelines

6.1 Infrared Reflow Soldering Profile

For lead-free (Pb-free) assembly processes, the following reflow conditions are suggested as a generic target, compliant with JEDEC standards:

• Pre-heat Temperature: 150°C to 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 Passes: Two.

Important Note: The optimal profile depends on the specific PCB design, solder paste, and oven. Characterization for the actual assembly line is recommended.

6.2 Hand Soldering

If manual soldering is necessary, use a temperature-controlled iron set to a maximum of 300°C. Contact time should be limited to 3 seconds per solder joint, and only one soldering pass should be performed.

6.3 Cleaning

Only alcohol-based solvents like isopropyl alcohol (IPA) or ethyl alcohol should be used for cleaning. The LED should be immersed at room temperature for less than one minute. Unspecified chemical cleaners may damage the epoxy package.

6.4 Storage and Handling

• ESD Precautions: The device is sensitive to electrostatic discharge (ESD). Use wrist straps, anti-static mats, and properly grounded equipment during handling.
• Moisture Sensitivity Level (MSL): The component is rated MSL3. Once the original moisture-barrier bag is opened, the LEDs must be subjected to IR reflow soldering within one week (168 hours) of factory conditions (≤30°C/60% RH).
• Extended Storage: For storage beyond one week after opening, bake the LEDs at 60°C for at least 20 hours before soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied for automated assembly in embossed carrier tape wound on 7-inch (178mm) diameter reels.

• Tape Width: 8mm.
• Quantity per Reel: 3000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Packaging Standard: Complies with ANSI/EIA-481 specifications.

8. Application Design Recommendations

8.1 Circuit Design

Always use a series current-limiting resistor for each anode. The resistor value (R_series) can be calculated using Ohm's Law: R_series = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet (2.4V) for a conservative design that ensures the current does not exceed 20mA even with supply voltage variations.

8.2 Thermal Management on PCB

Connect the thermal pad (cathode) to a sufficiently large copper area on the PCB to act as a heat sink. This helps dissipate heat, maintaining LED performance and longevity, especially when operating near maximum ratings.

8.3 Optical Design

The wide 130-degree viewing angle makes this LED suitable for applications requiring broad visibility. For focused illumination, external lenses or light guides may be necessary. The water-clear lens is optimal for true color emission.

9. Technical Comparison and Differentiation

The primary differentiating factor of the LTST-S327KGKFKT is the integration of two high-brightness AlInGaP chips (green and orange) in a single, miniature SMD package. Compared to using two separate single-color LEDs, this solution offers significant advantages:

• Space Savings: Reduces PCB footprint by approximately 50%.
• Simplified Assembly: One pick-and-place operation instead of two, lowering manufacturing cost and time.
• Alignment Consistency: Guarantees perfect spatial alignment between the two colored light sources, which is critical for certain indicator or backlighting designs.

10. Frequently Asked Questions (FAQ)

10.1 Can I drive both LED chips simultaneously at 20mA each?

Yes, but you must consider total power dissipation. Driving both at 20mA (V_F~2.0V) results in about 40mW per chip, totaling 80mW. This is above the 75mW absolute maximum rating per chip but refers to power dissipated within each semiconductor die. The combined board-level power is 80mW. For continuous operation, it is advisable to consult derating curves or drive the LEDs at a slightly lower current (e.g., 15-18mA) if both are on continuously.

10.2 What is the difference between peak wavelength (λ_P) and dominant wavelength (λ_d)?

Peak wavelength is the single wavelength at which the emission spectrum has its maximum intensity. Dominant wavelength is the single wavelength of monochromatic light that would appear to have the same color to the human eye as the LED's output. λ_d is calculated from the CIE chromaticity coordinates and is often the more relevant parameter for color specification.

10.3 How do I interpret the luminous intensity bin code?

The bin code (e.g., P, Q, N2) on the product label or tape reel indicates the guaranteed minimum and maximum luminous intensity for that batch of LEDs. For consistent brightness in your product, specify the required bin code when ordering. Using LEDs from different bins may result in visible brightness differences.

11. Design and Usage Case Study

11.1 Dual-State Status Indicator

Scenario: Designing a compact IoT sensor module with a single LED to indicate network status (green = connected, orange = searching/error).

Implementation: The LTST-S327KGKFKT is perfect for this. The microcontroller drives anode A1 (green) through a current-limiting resistor to indicate \"connected.\" It drives anode A2 (orange) to indicate \"searching.\" The common cathode is connected to ground. This design uses only one component footprint and one microcontroller GPIO pin per state (two pins total), maximizing space and simplifying firmware control compared to using two separate LEDs.

12. Operating Principle

The LED operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's threshold is applied, electrons from the n-type region recombine with holes from the p-type region within the active layer of the AlInGaP (Aluminum Indium Gallium Phosphide) chip. This recombination releases energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly defines the color (wavelength) of the emitted light—green for the shorter wavelength chip and orange for the longer wavelength chip. The water-clear epoxy package encapsulates and protects the semiconductor dice while also acting as a primary lens to shape the light output.

13. Technology Trends

The use of AlInGaP material systems represents a mature and highly efficient technology for producing red, orange, amber, and green LEDs. Key trends in this sector include:

• Increased Efficiency: Ongoing material science and chip design improvements continue to push luminous efficacy (lumens per watt) higher, reducing power consumption for a given light output.
• Miniaturization: The drive for smaller electronic devices fuels demand for ever-smaller LED packages while maintaining or improving optical performance.
• Integration: The trend exemplified by this component—integrating multiple chips or functions (e.g., RGB, LED+photodiode) into single packages—is growing to save space and simplify system design.
• Reliability and Standardization: Emphasis on robust packaging, strict binning, and standardized testing (like JEDEC reflow profiles) ensures consistent performance and reliability in high-volume automated manufacturing.