SMD LED LTST-T680KFWT Datasheet - White Diffused AlInGaP Orange - 30mA - 72mW - English Technical Document

1. Product Overview

This document details the specifications for a surface-mount device (SMD) LED. This component is designed for automated printed circuit board (PCB) assembly, making it suitable for space-constrained applications. Its miniature size and compatibility with standard assembly processes allow for integration into a wide array of electronic equipment.

1.1 Core Advantages and Target Market

The primary advantages of this LED include its compliance with RoHS regulations, packaging on 8mm tape within 7-inch reels for automated handling, and compatibility with infrared reflow soldering processes. It is designed to be integrated circuit (IC) compatible. The device is preconditioned to JEDEC Level 3 standards for moisture sensitivity. Its target applications span telecommunications, office automation, home appliances, and industrial equipment. Specific uses include status indicators, signal and symbol luminaires, and front panel backlighting.

2. Technical Parameters: In-Depth Objective Interpretation

This section provides a detailed breakdown of the device's operational limits and performance characteristics under standard test conditions.

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 ratings include a maximum power dissipation of 72 mW, a DC forward current of 30 mA, and a peak forward current of 80 mA under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). The device is rated for an operating temperature range of -40°C to +85°C and a storage temperature range of -40°C to +100°C.

2.2 Electrical and Optical Characteristics

Measured at an ambient temperature (Ta) of 25°C and a forward current (IF) of 20 mA, the device exhibits the following typical performance. The luminous intensity (Iv) has a wide range from a minimum of 140.0 mcd to a maximum of 450.0 mcd, with specific values determined by the bin rank. It features a wide viewing angle (2θ1/2) of 120 degrees. The peak emission wavelength (λP) is approximately 609 nm, with a dominant wavelength (λd) typically at 605 nm, defining its orange color perception. The spectral line half-width (Δλ) is 15 nm. The forward voltage (VF) ranges from 1.8V to 2.4V at the test current. The reverse current (IR) is specified at a maximum of 10 μA when a reverse voltage (VR) of 5V is applied, though the device is not designed for reverse operation.

3. Binning System Explanation

To ensure consistency in application, the LEDs are sorted into bins based on key parameters. This allows designers to select components that meet specific voltage, brightness, and color requirements.

3.1 Forward Voltage (VF) Rank

LEDs are categorized into three voltage bins (D2, D3, D4) with ranges of 1.8-2.0V, 2.0-2.2V, and 2.2-2.4V respectively, measured at 20mA. A tolerance of ±0.1V applies within each bin.

3.2 Luminous Intensity (IV) Rank

Brightness is classified into five bins (R2, S1, S2, T1, T2). The minimum luminous intensity ranges from 140.0 mcd (R2) to 355.0 mcd (T2), with corresponding maximums up to 450.0 mcd. A tolerance of ±11% applies.

3.3 Dominant Wavelength (WD) Rank

The color, defined by dominant wavelength, is sorted into four bins (P, Q, R, S) covering the range from 600 nm to 612 nm. The tolerance for dominant wavelength is ±1 nm.

4. Performance Curve Analysis

While specific graphical data is referenced in the source document, typical curves for such devices illustrate the relationship between forward current and forward voltage (IV curve), the variation of luminous intensity with ambient temperature, and the spectral power distribution showing the peak wavelength and spectral width. These curves are essential for understanding device behavior under non-standard conditions and for circuit design.

5. Mechanical and Package Information

5.1 Package Dimensions and Polarity Identification

The LED comes in a standard EIA package. Detailed dimensional drawings specify the length, width, height, and lead positions. The cathode is typically identified by a marking on the package or a specific pad geometry. All dimensions are provided in millimeters with a standard tolerance of ±0.2 mm unless otherwise noted.

5.2 Recommended PCB Attachment Pad Layout

A land pattern design is recommended for infrared or vapor phase reflow soldering. This pattern ensures proper solder joint formation, thermal relief, and mechanical stability during and after the assembly process.

6. Soldering and Assembly Guidelines

6.1 Recommended IR Reflow Profile

For lead-free soldering processes, a profile compliant with J-STD-020B is suggested. Key parameters include a pre-heat zone, a defined time above liquidus, and a peak temperature not exceeding 260°C. The total time within 5°C of the peak temperature should be limited. Because board design variables affect the thermal profile, board-specific characterization is recommended.

6.2 Storage Conditions

Unopened moisture-sensitive bags should be stored at ≤30°C and ≤70% relative humidity (RH), with a recommended use-within period of one year. Once opened, components should be stored at ≤30°C and ≤60% RH. It is recommended to complete IR reflow within 168 hours of opening the bag. For storage beyond this period, baking at approximately 60°C for at least 48 hours before assembly is advised.

6.3 Cleaning

If cleaning is necessary after soldering, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute is acceptable. Unspecified chemicals may damage the package.

6.4 Drive Method

LEDs are current-operated devices. To ensure stable luminous intensity and longevity, they must be driven by a constant current source or with a current-limiting resistor in series when using a voltage source. The forward current must not exceed the absolute maximum DC rating of 30 mA.

7. Packaging and Handling Information

The components are supplied on 8mm wide embossed carrier tape sealed with cover tape, wound onto 7-inch (178mm) diameter reels. Each reel contains 2000 pieces. The packaging conforms to ANSI/EIA 481 specifications. A minimum packing quantity of 500 pieces applies for remainder quantities. Detailed dimensions for the tape pocket and the reel are provided.

8. Application Suggestions

8.1 Typical Application Scenarios

This LED is well-suited for status indication in consumer electronics (phones, laptops, appliances), backlighting for front panels and symbols, and low-level general illumination in signs. Its wide viewing angle makes it effective for applications where visibility from multiple angles is important.

8.2 Design Considerations

Thermal Management: Although power dissipation is low, ensuring adequate PCB copper area or thermal vias can help maintain lower junction temperatures, preserving luminous output and lifespan.
Current Limiting: Always use a series resistor or constant current driver tailored to the supply voltage and desired forward current (≤30mA).
ESD Protection: Standard ESD precautions should be observed during handling and assembly.
Optical Design: The "white diffused" lens provides a softened, wide-angle light emission. For focused or directed light, secondary optics may be required.

9. Technical Comparison and Differentiation

Compared to older LED technologies, the use of AlInGaP (Aluminum Indium Gallium Phosphide) material for an orange source typically offers higher efficiency and better temperature stability of wavelength and output compared to some other material systems for colors in the red-orange-amber range. The combination with a white diffused lens creates a uniform, soft orange appearance, differentiating it from clear-lens LEDs which have a more focused, intense hotspot.

10. Frequently Asked Questions Based on Technical Parameters

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength is the single wavelength at which the emitted optical power is maximum. Dominant wavelength is the single wavelength of monochromatic light that matches the perceived color of the LED when compared to a reference white light. Dominant wavelength is more relevant for color specification.

Q: Can I drive this LED at 30mA continuously?
A: The Absolute Maximum Rating specifies 30mA DC as the upper limit. For reliable long-term operation, it is common practice to drive LEDs below their maximum rating, often at 20mA as used in the test conditions, to enhance longevity and manage thermal effects.

Q: Why is the reverse current specification important if the device is not for reverse operation?
A: This specification is primarily for test purposes (IR test) and indicates the device's leakage characteristic. It underscores that applying a reverse voltage can cause current to flow and potentially damage the LED, so circuit design must prevent reverse bias.

11. Practical Design and Usage Case

Scenario: Designing a multi-status indicator panel. A designer needs three distinct brightness levels (Low, Medium, High) for an orange status indicator on a device powered by a 5V rail. Using the T680KFWT LED from the T2 brightness bin (355-450 mcd), they can achieve High brightness by driving at 20mA. For Medium and Low, they can use pulse-width modulation (PWM) at a frequency high enough to avoid visible flicker (e.g., >100Hz) with duty cycles of, for example, 50% and 10%, respectively. This maintains color consistency while varying perceived brightness. A simple series resistor value would be calculated as R = (5V - VF) / 0.020A. Using a typical VF of 2.0V (from bin D2), R = (5-2)/0.02 = 150 ohms. A 150-ohm, 1/8W resistor would be sufficient.

12. Operating Principle Introduction

Light-emitting diodes are semiconductor devices that emit light through electroluminescence. When a forward voltage is applied across the p-n junction, electrons from the n-type region and holes from the p-type region are injected into the active region. When these charge carriers recombine, energy is released in the form of photons. The specific wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material used in the active region. In this device, AlInGaP is used to produce photons in the orange wavelength range (~605 nm). The epoxy lens is doped with diffuser particles to scatter the light, creating a wider, more uniform emission pattern.

13. Industry Trends and Developments

The general trend in SMD LEDs continues toward higher luminous efficacy (more light output per electrical watt), improved color consistency through tighter binning, and enhanced reliability. There is also a focus on developing packages that can withstand higher temperature reflow profiles required for lead-free soldering and assembly with other components. Miniaturization remains a key driver, alongside integration with control electronics. The principles of solid-state lighting, including efficiency and longevity, continue to make LEDs the dominant solution for indicator and illumination applications across all sectors.