SMD LED LTST-S115KSKRKT Datasheet - Side Looking Dual Color (Yellow/Red) - AlInGaP Chip - 25mA - 62.5mW - English Technical Document

1. Product Overview

This document details the specifications for a compact, surface-mount dual-color LED lamp. Designed for automated assembly, this component is ideal for applications where space is at a premium and reliable, bright indication is required. The device integrates two distinct light-emitting chips within a single, industry-standard package.

1.1 Features

• Compliant with RoHS environmental directives.
• Dual-color configuration (Yellow and Red) in a side-looking package.
• Utilizes high-brightness Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor technology.
• Terminals feature tin plating for improved solderability.
• Packaged on 8mm tape wound onto 7-inch diameter reels for automated pick-and-place equipment.
• Conforms to standard EIA package outlines.
• Input logic is compatible with standard integrated circuit (IC) drive levels.
• Fully compatible with automated placement and infrared (IR) reflow soldering processes.

1.2 Applications

This LED is suited for a broad range of electronic devices and systems, including but not limited to:

• Telecommunication equipment (e.g., cordless/cellular phones, network switches).
• Office automation devices (e.g., notebooks, printers).
• Home appliances and industrial control panels.
• Backlighting for keypads and keyboards.
• Status and power indicators.
• Micro-displays and symbolic illumination.

2. Technical Parameters: In-Depth Objective Interpretation

2.1 Absolute Maximum Ratings

These values represent the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed.

• Power Dissipation (P_d): 62.5 mW per chip. This is the maximum power the LED can dissipate as heat at an ambient temperature (T_a) of 25°C. Exceeding this limit risks thermal degradation.
• Peak Forward Current (I_FP): 60 mA. This is the maximum allowable instantaneous current, typically specified under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to prevent overheating the semiconductor junction.
• Continuous Forward Current (I_F): 25 mA DC. This is the recommended maximum current for continuous operation, ensuring long-term reliability and stable light output.
• Reverse Voltage (V_R): 5 V. Applying a reverse bias voltage exceeding this rating can cause immediate and catastrophic failure of the LED junction.
• Operating Temperature Range: -30°C to +80°C. The device is guaranteed to function within this ambient temperature range.
• Storage Temperature Range: -40°C to +100°C. The device can be stored without degradation within these limits.
• Infrared Soldering Condition: Withstands a peak temperature of 260°C for a maximum of 10 seconds, which is standard for lead-free (Pb-free) solder reflow profiles.

2.2 Electro-Optical Characteristics

These parameters are measured at T_a=25°C and I_F=20mA, representing typical operating conditions.

• Luminous Intensity (I_V):
  • Yellow: Minimum 45.0 mcd, Typical value provided, Maximum 180.0 mcd.
  • Red: Minimum 28.0 mcd, Typical value provided, Maximum 180.0 mcd.
  • Measured using a sensor filtered to match the human eye's photopic response (CIE 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 (on-axis) value. A wide 130° angle makes this a side-emitting device suitable for broad, even illumination.
• Peak Emission Wavelength (λ_P):
  • Yellow: Typically 593 nm.
  • Red: Typically 639 nm.
  • This is the wavelength at which the optical output power is greatest.
• Dominant Wavelength (λ_d):
  • Yellow: Range from 587.0 nm (Min) to 594.5 nm (Max).
  • Red: Range from 624 nm (Min) to 638 nm (Max).
  • Derived from the CIE chromaticity diagram, this is the single wavelength perceived by the human eye to define the color.
• Spectral Line Half-Width (Δλ): Typically 15 nm (Yellow) and 20 nm (Red). This indicates the spectral purity; a smaller value means a more monochromatic light.
• Forward Voltage (V_F): Typically 2.0 V, with a maximum of 2.4 V at 20mA for both colors. This is the voltage drop across the LED when operating.
• Reverse Current (I_R): Maximum 10 μA at V_R=5V. This is the small leakage current when the device is reverse-biased within its rating.

3. Bin Ranking System Explanation

The luminous intensity of LEDs varies from batch to batch. A binning system ensures consistency by grouping devices with similar performance.

3.1 Luminous Intensity Binning

Each color has specific bin codes defining minimum and maximum luminous intensity ranges at 20mA. Tolerance within each bin is +/-15%.

Yellow Chip:

• Bin P: 45.0 – 71.0 mcd
• Bin Q: 71.0 – 112.0 mcd
• Bin R: 112.0 – 180.0 mcd

Red Chip:

• Bin N: 28.0 – 45.0 mcd
• Bin P: 45.0 – 71.0 mcd
• Bin Q: 71.0 – 112.0 mcd
• Bin R: 112.0 – 180.0 mcd

Designers should specify the required bin code(s) when ordering to guarantee the necessary brightness level for their application.

4. Mechanical and Packaging Information

4.1 Package Dimensions and Pin Assignment

The device conforms to a standard SMD outline. Critical dimensions include body size and lead spacing. All dimensions are in millimeters with a typical tolerance of ±0.1mm.

Pin Assignment:

• Cathode 1 (C1): Connected to the Red chip's anode. The common cathode configuration means applying forward voltage to C1 (relative to the common anode) illuminates the Red chip.
• Cathode 2 (C2): Connected to the Yellow chip's anode. Applying forward voltage to C2 illuminates the Yellow chip.
• Common Anode: The other terminal (not explicitly labeled C1/C2 in the diagram) is the shared anode for both chips.

This configuration allows independent control of the two colors by driving the respective cathode pins.

4.2 Recommended PCB Pad Layout and Soldering Direction

A recommended land pattern (footprint) is provided to ensure proper solder joint formation, mechanical stability, and thermal relief during reflow. The orientation of the device on the tape relative to the PCB pads is also indicated to facilitate correct automated placement.

4.3 Tape and Reel Packaging Specifications

The LEDs are supplied in embossed carrier tape for automated handling.

• Tape Width: 8 mm.
• Reel Diameter: 7 inches (178 mm).
• Quantity per Reel: 3000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for partial reels.
• The packaging follows ANSI/EIA-481 standards. The tape is sealed with a cover tape, and a maximum of two consecutive empty pockets is allowed.

5. Soldering, Assembly, and Handling Guidelines

5.1 Infrared Reflow Soldering Profile

A detailed temperature vs. time profile is recommended for lead-free (Pb-free) solder assembly. Key parameters include:

• Pre-heat: Ramp-up to 150-200°C.
• Soak/Pre-heat Time: Maximum 120 seconds to activate flux and equalize temperature.
• Reflow (Liquidus): Peak temperature must not exceed 260°C.
• Time Above 260°C: Must be 10 seconds or less.
• Number of Reflow Passes: Maximum of two times.

The profile should be developed in conjunction with the specific solder paste manufacturer's guidelines and validated for the actual PCB assembly.

5.2 Hand Soldering

If manual soldering is necessary:

• Iron Temperature: Maximum 300°C.
• Contact Time: Maximum 3 seconds per solder joint.
• Number of Times: One time only per joint to minimize thermal stress.

5.3 Cleaning

If post-solder cleaning is required:

• Use only specified solvents such as ethyl alcohol or isopropyl alcohol.
• Immersion time should be less than one minute at room temperature.
• Avoid aggressive or unspecified chemicals that may damage the LED lens or package material.

5.4 Storage and Moisture Sensitivity

The LEDs are moisture-sensitive. Proper handling is critical to prevent "popcorning" (package cracking) during reflow.

• Sealed Package: Store at ≤30°C and ≤90% RH. Use within one year of the dry-pack date.
• Opened Package: Store at ≤30°C and ≤60% RH. For extended storage outside the original bag, use a sealed container with desiccant or a nitrogen atmosphere.
• Floor Life: Components exposed to ambient air for more than one week should be baked at approximately 60°C for at least 20 hours before soldering to remove absorbed moisture.

5.5 Electrostatic Discharge (ESD) Precautions

The AlInGaP semiconductor structure is susceptible to damage from electrostatic discharge (ESD) and electrical surges.

• Always handle components in an ESD-protected area.
• Use wrist straps or anti-static gloves.
• Ensure all equipment, tools, and work surfaces are properly grounded.

6. Application Notes and Design Considerations

6.1 Current Limiting

An external current-limiting resistor is mandatory when driving the LED from a voltage source higher than its forward voltage (V_F). The resistor value can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F. For reliable operation, do not exceed the continuous forward current (I_F) of 25mA. For pulsed operation to achieve higher perceived brightness, ensure the peak current and duty cycle stay within the Absolute Maximum Ratings.

6.2 Thermal Management

While the power dissipation is relatively low (62.5mW per chip), proper thermal design extends lifespan and maintains stable light output. Ensure the PCB pad design provides adequate thermal relief. Avoid placing the LED near other significant heat sources. Operating at high ambient temperatures (towards the maximum 80°C) may require derating the maximum forward current.

6.3 Optical Design

The 130-degree side-viewing angle is a key feature. When designing light guides, lenses, or diffusers, this wide emission pattern should be considered to achieve uniform illumination. The "water clear" lens provides the true chip color without diffusion.

7. Technical Comparison and Differentiation

This device offers specific advantages in its category:

• Dual Color in One Package: Saves PCB space and component count compared to using two separate single-color LEDs.
• AlInGaP Technology: Provides higher efficiency and brightness compared to older technologies like standard GaAsP for red/yellow colors, especially at lower currents.
• Side-Viewing Package: Ideal for applications where the PCB is mounted parallel to the viewing surface, such as in edge-lit panels or status indicators on the side of a device.
• Full IR Reflow Compatibility: Can withstand standard lead-free soldering profiles, making it suitable for modern, high-volume SMT assembly lines without requiring secondary processes.

8. Frequently Asked Questions (Based on Technical Parameters)

8.1 Can I drive both the Yellow and Red chips simultaneously?

Yes, but you must consider the total power dissipation. The Absolute Maximum Rating for power dissipation is 62.5mW per chip. Driving both chips at their maximum continuous current (25mA each) with a typical V_F of 2.0V results in 50mW per chip (100mW total), which exceeds the per-chip rating. Therefore, to drive both simultaneously, you must reduce the current to each chip so that the individual power dissipation does not exceed 62.5mW. A safe approach is to limit the current to each chip to a value that keeps P_d within spec, e.g., ~15mA each.

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

Peak Wavelength (λ_P): The physical wavelength where the LED emits the most optical power. It is measured directly by a spectrometer. Dominant Wavelength (λ_d): A calculated value based on the CIE color chart that represents the single wavelength the human eye perceives the color to be. For monochromatic LEDs like these, λ_P and λ_d are usually very close. λ_d is more relevant for color specification in human-centric applications.

8.3 Why is the storage humidity requirement so strict after opening the bag?

The plastic LED package can absorb moisture from the air. During the high-temperature reflow soldering process, this absorbed moisture rapidly turns to steam, creating internal pressure that can delaminate the package or crack the epoxy lens ("popcorning"). The strict humidity controls and baking requirements are standard for moisture-sensitive devices (MSD) per industry standards like JEDEC J-STD-033.