SMD LED LTST-E682KGKFWT Datasheet - Package Dimensions - Forward Voltage 1.8-2.4V - Luminous Intensity up to 450mcd - English Technical Document

1. Product Overview

This document details the specifications for a surface-mount device (SMD) LED designed for automated printed circuit board (PCB) assembly. The component is characterized by its miniature size, making it suitable for space-constrained applications across a broad spectrum of electronic equipment.

1.1 Core Advantages and Target Market

The primary advantages of this LED include its compliance with environmental regulations, compatibility with standard automated manufacturing processes, and robust packaging for handling and storage. It is specifically engineered for integration into telecommunication devices, office automation equipment, home appliances, and industrial control systems. Its primary functions are status indication, signal and symbol illumination, and front panel backlighting.

1.2 Key Features

• Compliant with Restriction of Hazardous Substances (RoHS) directives.
• Packaged in 8mm tape on 7-inch diameter reels, facilitating high-speed pick-and-place assembly.
• Standardized EIA package footprint ensures compatibility with industry-standard PCB layouts.
• Integrated circuit (IC) compatible drive characteristics.
• Fully compatible with automatic placement equipment.
• Withstands infrared (IR) reflow soldering processes as per industry profiles.
• Preconditioned to JEDEC Moisture Sensitivity Level 3, indicating a floor life of 168 hours at <30°C/60% RH after the bag is opened.

2. Technical Parameters: In-Depth Objective Interpretation

The following sections provide a detailed analysis of the LED's electrical, optical, and thermal characteristics based on the provided data.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation at or near these limits is not recommended for reliable design.

• Power Dissipation (P_d): 72 mW maximum for both orange and green chips. This parameter limits the combination of forward current and voltage.
• Peak Forward Current (I_FP): 80 mA, permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This is relevant for multiplexing or brief signal bursts.
• Continuous Forward Current (I_F): 30 mA DC. This is the recommended maximum current for steady-state operation.
• Reverse Voltage (V_R): 5 V maximum. Exceeding this can cause junction breakdown.
• Operating & Storage Temperature: -40°C to +85°C for operation, and -40°C to +100°C for storage. These ranges are typical for commercial-grade components.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured under standard test conditions (Ta=25°C, I_F=20mA).

• Luminous Intensity (I_V): Orange: 140-450 mcd (millicandela). Green: 71-224 mcd. Measured with a filter approximating the photopic (human eye) response. The wide range indicates a binning system is used (see Section 3).
• Viewing Angle (2θ_1/2): 120 degrees (typical). This wide angle, facilitated by the diffused lens, provides a broad, even illumination pattern rather than a narrow beam.
• Peak Wavelength (λ_P): Orange: 611 nm. Green: 574 nm. This is the wavelength at which the emitted optical power is greatest.
• Dominant Wavelength (λ_d): Orange: 605 nm. Green: 571 nm. This is the single wavelength perceived by the human eye, defining the color point on the CIE chromaticity diagram.
• Spectral Bandwidth (Δλ): Orange: 17 nm. Green: 15 nm. This indicates the spectral purity of the light; a narrower bandwidth means a more saturated color.
• Forward Voltage (V_F): 1.8 V to 2.4 V for both colors at 20mA. Designers must account for this voltage drop when calculating series current-limiting resistors.
• Reverse Current (I_R): 10 μA maximum at V_R=5V. A low value indicates good junction quality.

3. Binning System Explanation

To ensure consistent brightness in production, LEDs are sorted (binned) based on their luminous intensity. The tolerance within each bin is +/-11%.

3.1 Luminous Intensity Binning

Orange LED Bins: R2 (140-180 mcd), S1 (180-224 mcd), S2 (224-280 mcd), T1 (280-355 mcd), T2 (355-450 mcd).
Green LED Bins: Q1 (71-90 mcd), Q2 (90-112 mcd), R1 (112-140 mcd), R2 (140-180 mcd), S1 (180-224 mcd).
This system allows designers to select the appropriate brightness grade for their application, balancing cost and performance.

4. Performance Curve Analysis

While specific graphs are referenced in the datasheet, their implications are critical for design.

4.1 Forward Current vs. Forward Voltage (I-V Curve)

The I-V characteristic is non-linear, typical of a diode. The forward voltage has a negative temperature coefficient, meaning V_F decreases slightly as junction temperature increases. This must be considered in constant-current drive designs.

4.2 Luminous Intensity vs. Forward Current

Luminous intensity is approximately proportional to forward current within the recommended operating range. However, efficiency (lumens per watt) may decrease at very high currents due to increased heat.

4.3 Spectral Distribution

The referenced spectral distribution curves would show the narrow emission peaks characteristic of AlInGaP technology, centered around the stated peak wavelengths, confirming the color purity.

5. Mechanical and Package Information

5.1 Package Dimensions and Pin Assignment

The LED utilizes a standard SMD footprint. Critical dimensions include body size and lead spacing. All dimensions are in millimeters with a typical tolerance of ±0.2 mm. The pin assignment is clearly defined: Pins 1 and 2 are for the green LED chip, and pins 3 and 4 are for the orange LED chip. This dual-chip, 4-pin configuration allows for independent control of the two colors.

5.2 Recommended PCB Attachment Pad

A land pattern diagram is provided to ensure proper solder joint formation and mechanical stability. Adhering to this recommendation is crucial for achieving reliable solder connections during reflow and preventing tombstoning or misalignment.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Profile

A suggested reflow profile compliant with J-STD-020B for lead-free processes is provided. Key parameters include a preheat zone (150-200°C for up to 120 sec max), a peak package body temperature not exceeding 260°C, and a time above liquidus (TAL) limited to ensure proper solder joint formation without thermal damage to the LED package or epoxy lens.

6.2 Storage and Handling Cautions

• Storage (Sealed Bag): ≤30°C and ≤70% RH. Use within one year.
• Storage (After Opening): ≤30°C and ≤60% RH. Complete IR reflow within 168 hours (1 week).
• Extended Storage (Opened): Store in a sealed container with desiccant or in a nitrogen atmosphere.
• Baking: If exposed for >168 hours, bake at 60°C for at least 48 hours before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

6.3 Cleaning

Only specified cleaning agents should be used. Isopropyl alcohol or ethyl alcohol is recommended. Immersion should be at normal temperature and for less than one minute to prevent damage to the package materials.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The components are supplied on embossed carrier tape, 8mm wide, wound onto 7-inch (178mm) diameter reels. Standard reel quantity is 2000 pieces. A minimum packing quantity of 500 pieces is available for remainder orders. The packaging conforms to ANSI/EIA-481 specifications.

8. Application Suggestions

8.1 Typical Application Scenarios

• Status Indicators: Power on/off, network activity, battery charging, system ready.
• Backlighting: Illumination of keypads, icons, or symbols on front panels.
• Signal Luminaires: Simple color-coded messages (e.g., green for OK, orange for warning).

8.2 Design Considerations

• Current Limiting: Always use a series resistor or constant-current driver to set the forward current. Calculate resistor value using R = (V_supply - V_F) / I_F.
• Thermal Management: While power dissipation is low, ensure adequate PCB copper area or thermal vias if operating at high ambient temperatures or maximum current to maintain junction temperature within limits.
• ESD Protection: Standard ESD precautions should be observed during handling and assembly.

9. Technical Comparison and Differentiation

This LED's key differentiators are its use of AlInGaP semiconductor material and a diffused lens. AlInGaP technology typically offers higher luminous efficiency and better temperature stability for amber/orange/red colors compared to older technologies like GaAsP. The diffused lens provides a very wide (120°) and uniform viewing angle, which is advantageous for applications where the LED may be viewed from various angles, as opposed to a narrow-angle LED used for directed light.

10. Frequently Asked Questions Based on Technical Parameters

10.1 Can I drive this LED at 30mA continuously?

Yes, 30mA is the maximum rated continuous DC forward current. For optimal longevity and stable performance, operating at a lower current, such as 20mA (the test condition), is often recommended.

10.2 Why is there a range for luminous intensity and forward voltage?

Manufacturing variations cause natural spreads in these parameters. The binning system (Section 3) sorts LEDs by intensity. Forward voltage has a specified tolerance of +/- 0.1V from the typical value at a given current. Circuit designs must accommodate these ranges.

10.3 How do I control the two colors independently?

The LED has two separate semiconductor chips (one green, one orange) with independent anode/cathode connections (pins 1-2 for green, 3-4 for orange). You need two separate drive circuits (e.g., two current-limiting resistors connected to different microcontroller GPIO pins) to control them individually.

11. Practical Design and Usage Case

Case: Dual-Status Indicator for a Network Device. A designer needs a single component to show "Connected" (green) and "Data Transferring" (orange) statuses. This LED is ideal. The green chip is connected to a GPIO pin set high when the link is established. The orange chip is connected to another GPIO pin that is pulsed (e.g., using the 80mA peak current rating) in sync with data activity. The wide viewing angle ensures the status is visible from anywhere in front of the device. The designer selects an R2 bin for green and an S1 bin for orange to ensure sufficient but balanced brightness, and uses 20mA drive currents with appropriate series resistors calculated based on the 2.1V typical V_F and the 3.3V system supply.

12. Principle Introduction

This LED is based on Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor technology. 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 composition of the AlInGaP alloy determines the bandgap energy and thus the wavelength (color) of the emitted light—in this case, green and orange. The diffused lens is made of epoxy resin with scattering particles that randomize the direction of the emitted light, creating a wide, Lambertian-like emission pattern.

13. Development Trends

The general trend in SMD indicator LEDs continues toward higher luminous efficacy (more light output per electrical watt), improved color consistency through tighter binning, and enhanced reliability under higher temperature soldering processes. There is also a drive for miniaturization while maintaining or increasing optical performance. The use of advanced semiconductor materials like AlInGaP for specific color ranges represents an ongoing effort to optimize efficiency and color purity for indicator applications.