SMD LED LTST-T680VEWT Datasheet - AlInGaP Red - 120° Viewing Angle - 2.1V Typ - 50mA - 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 engineered for space-constrained applications across a broad spectrum of electronic equipment. Its miniature form factor and compatibility with standard assembly processes make it suitable for integration into modern consumer and industrial electronics where reliable status indication or backlighting is required.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Packaged in 8mm tape on 7-inch diameter reels for automated pick-and-place machinery.
• Standard EIA (Electronic Industries Alliance) package outline.
• Input/output compatible with integrated circuit (IC) logic levels.
• Designed for compatibility with automatic placement equipment.
• Suitable for infrared (IR) reflow soldering processes.
• Preconditioned to accelerate to JEDEC (Joint Electron Device Engineering Council) Moisture Sensitivity Level 3.

1.2 Applications

• Telecommunication equipment (e.g., cordless phones, cellular phones).
• Office automation devices (e.g., notebook computers, network systems).
• Home appliances and consumer electronics.
• Industrial control and instrumentation panels.
• General-purpose status and power indicators.
• Signal and symbol illumination.
• Front panel and display backlighting.

2. Package and Dimensions

The LED utilizes a diffused lens material with an AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material as the light source, producing a red color. The package dimensions are provided in detailed mechanical drawings (refer to the original datasheet for figures). All primary dimensions are specified in millimeters (mm) with a standard tolerance of ±0.2 mm unless otherwise stated. The component is polarity-sensitive, and correct orientation during placement is crucial for proper operation.

3. Ratings and Characteristics

3.1 Absolute Maximum Ratings

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

• Power Dissipation (Pd): 130 mW
• Peak Forward Current (IFP): 100 mA (at 1/10 duty cycle, 0.1ms pulse width)
• DC Forward Current (IF): 50 mA
• Reverse Voltage (VR): 5 V
• Operating Temperature Range (Topr): -40°C to +85°C
• Storage Temperature Range (Tstg): -40°C to +100°C

3.2 Suggested IR Reflow Profile

For lead-free (Pb-free) soldering processes, a reflow profile compliant with J-STD-020B is recommended. The profile typically includes a preheat stage, a thermal soak, a reflow zone with a peak temperature, and a cooling phase. Adherence to the specified time and temperature limits, particularly the maximum peak temperature of 260°C, is essential to prevent thermal damage to the LED package and ensure reliable solder joints.

3.3 Electrical and Optical Characteristics

Typical performance parameters are measured at Ta=25°C and a forward current (IF) of 20mA, unless otherwise noted.

• Luminous Intensity (Iv): 710.0 - 1400.0 mcd (millicandela). Measured with a filter approximating the CIE photopic eye-response curve.
• Viewing Angle (2θ1/2): 120 degrees (typical). Defined as the full angle at which luminous intensity is half the axial (on-axis) intensity.
• Peak Emission Wavelength (λP): 633 nm (nanometers, typical). The wavelength at which the spectral power distribution is maximum.
• Dominant Wavelength (λd): 624 nm (typical). The single wavelength perceived by the human eye, derived from the CIE chromaticity diagram. Tolerance is ±1 nm.
• Spectral Line Half-Width (Δλ): 15 nm (typical). The spectral width at half the maximum intensity.
• Forward Voltage (VF): 2.1 V (typical), 2.6 V (maximum). Tolerance is ±0.1 V at IF=20mA.
• Reverse Current (IR): 10 μA (microamperes, maximum) at VR=5V.

4. Bin Rank System

To ensure consistency in brightness for production applications, LEDs are sorted into bins based on luminous intensity measured at 20mA.

• Bin Code V1: 710.0 mcd (Min) to 900.0 mcd (Max)
• Bin Code V2: 900.0 mcd (Min) to 1120.0 mcd (Max)
• Bin Code W1: 1120.0 mcd (Min) to 1400.0 mcd (Max)

The tolerance within each intensity bin is approximately ±11%. Designers should account for this variation when multiple LEDs are used in an array to achieve uniform appearance.

5. Typical Performance Curves

The datasheet includes graphical representations of key relationships (refer to original figures). These typically illustrate:

• Relative Luminous Intensity vs. Forward Current: Shows how light output increases with current, usually in a non-linear fashion, highlighting the importance of current regulation.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the decrease in light output as junction temperature rises, a critical factor for thermal management.
• Forward Voltage vs. Forward Current: Depicts the I-V characteristic curve of the diode.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the narrow emission band characteristic of AlInGaP LEDs centered around 633 nm.

6. User Guide and Handling

6.1 Cleaning

If cleaning is necessary after soldering or due to contamination, use only specified solvents. Immerse the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute. Do not use ultrasonic cleaning or unspecified chemical liquids, as they may damage the epoxy lens or package.

6.2 Recommended PCB Pad Layout

A suggested land pattern (footprint) for the PCB is provided to ensure proper solder fillet formation and mechanical stability during infrared or vapor phase reflow soldering. Following this recommendation helps prevent tombstoning (component standing up on one end) and ensures reliable electrical connection.

6.3 Packaging: Tape and Reel

The LEDs are supplied in embossed carrier tape with a protective cover tape, wound onto 7-inch (178 mm) diameter reels. Key specifications include:

• Pocket Pitch: 8 mm.
• Quantity per Reel: 2000 pieces.
• Maximum Consecutive Missing Components: Two pockets.
• Packaging conforms to ANSI/EIA-481 specifications.

This packaging format is standard for high-speed automated assembly lines.

7. Important Cautions and Application Notes

7.1 Intended Application

This LED is designed for use in standard commercial and industrial electronic equipment. It is not intended for safety-critical applications where failure could directly jeopardize life or health (e.g., aviation, medical life-support, transportation control). For such applications, consultation with the manufacturer for components with exceptional reliability qualifications is mandatory.

7.2 Storage Conditions

Proper storage is vital to prevent moisture absorption, which can cause \"popcorning\" (package cracking) during reflow soldering.

• Sealed Package: Store at ≤30°C and ≤70% Relative Humidity (RH). Use within one year.
• Opened Package: If the moisture barrier bag is opened, the components should be stored at ≤30°C and ≤60% RH. It is strongly recommended to complete the IR reflow process within 168 hours (7 days) of exposure.
• Extended Storage (Opened): For storage beyond 168 hours, place components in a sealed container with desiccant or in a nitrogen desiccator. Components stored out of bag for more than 168 hours require a baking preconditioning of at least 48 hours at approximately 60°C before soldering to drive out absorbed moisture.

7.3 Soldering Recommendations

Adhere to the following soldering conditions to prevent thermal damage:

• Reflow Soldering:
  • Preheat: 150–200°C
  • Preheat Time: 120 seconds maximum
  • Peak Temperature: 260°C maximum
  • Time above Liquidus: 10 seconds maximum (maximum two reflow cycles allowed)
• Hand Soldering (Soldering Iron):
  • Iron Tip Temperature: 300°C maximum
  • Contact Time: 3 seconds maximum (one time only per lead)

Note that the optimal reflow profile depends on the specific PCB design, solder paste, and oven. The provided profile based on JEDEC standards serves as a generic target.

7.4 Drive Circuit Design

LEDs are current-operated devices. Their forward voltage (VF) has a tolerance and a negative temperature coefficient. To ensure uniform brightness when driving multiple LEDs, especially in parallel, a current-limiting resistor must be used in series with each LED. Driving LEDs in parallel without individual resistors (as in Circuit Model B) is not recommended, as small variations in VF will cause significant differences in current sharing and, consequently, luminous intensity.

7.5 Electrostatic Discharge (ESD) Sensitivity

Like most semiconductor devices, LEDs are susceptible to damage from electrostatic discharge. Standard ESD handling precautions should be observed during assembly and handling. This includes the use of grounded workstations, wrist straps, and conductive containers.

8. Technical Deep Dive and Design Considerations

8.1 Material Technology: AlInGaP

The use of Aluminum Indium Gallium Phosphide (AlInGaP) as the active semiconductor material is key to this LED's performance. AlInGaP technology enables high-efficiency emission in the red to amber-orange region of the visible spectrum. Compared to older technologies like GaAsP, AlInGaP LEDs offer superior luminous efficacy, better temperature stability, and longer operational lifetime. The diffused lens further broadens the viewing angle to 120 degrees, making it ideal for applications requiring wide-angle visibility.

8.2 Thermal Management

The maximum power dissipation is 130 mW. While this seems low, effective heat sinking through the PCB is still important. The LED's luminous intensity decreases as its junction temperature increases, as shown in the performance curves. For designs operating at high ambient temperatures or near the maximum forward current, ensuring adequate thermal relief in the PCB pad design (e.g., thermal vias to inner ground planes) can help maintain consistent brightness and longevity.

8.3 Optical Design Integration

The 120-degree viewing angle with a diffused lens provides a soft, wide beam suitable for indicator applications where the LED may be viewed from various angles. Designers should consider this beam pattern when designing light guides, lenses, or bezels to avoid creating unwanted hotspots or shadows. The dominant wavelength of 624 nm falls in the red-orange region, which is highly visible to the human eye and is a standard color for \"power on\" or \"active\" status indicators.

8.4 Reliability and Lifespan

The specified operating temperature range of -40°C to +85°C and storage range up to 100°C indicate robust construction. The preconditioning to JEDEC Level 3 suggests the package can withstand typical factory floor conditions for a limited time. Long-term reliability is influenced by operating current and junction temperature; derating the operating current from the absolute maximum of 50mA will significantly extend the device's operational life.

9. Comparison and Selection Guidance

When selecting an SMD LED for a red indicator application, key differentiators include:

• Viewing Angle: This component's 120° angle is wider than many standard LEDs (often 60-90°), offering better off-axis visibility.
• Intensity Binning: The availability of multiple intensity bins (V1, V2, W1) allows designers to select the appropriate brightness level for their application, potentially optimizing cost.
• Forward Voltage: A typical VF of 2.1V is relatively low, reducing power consumption and easing design for low-voltage systems compared to some other LED technologies.
• Package Compatibility: The EIA-standard package ensures compatibility with a vast library of existing PCB footprints and pick-and-place nozzle libraries.

10. Frequently Asked Questions (FAQ)

Q: Can I drive this LED directly from a 3.3V or 5V logic output?
A: No. You must use a series current-limiting resistor. For example, with a 5V supply and a target current of 20mA, using the typical VF of 2.1V, the resistor value would be R = (5V - 2.1V) / 0.02A = 145 Ohms. A standard 150 Ohm resistor would be suitable.

Q: What is the difference between Peak Wavelength and Dominant Wavelength?
A: Peak Wavelength (λP) is the physical wavelength where the LED emits the most optical power. Dominant Wavelength (λd) is the perceptual single wavelength that matches the color seen by the human eye, calculated from the CIE color coordinates. λd is often more relevant for color specification.

Q: Why is storage humidity so critical?
A: The plastic LED package can absorb moisture. During the high-temperature reflow soldering process, this trapped moisture can vaporize rapidly, creating internal pressure that can delaminate the package or crack the epoxy lens, leading to immediate or latent failure.

Q: How do I interpret the luminous intensity value (e.g., 900 mcd)?
A: Luminous intensity measures the perceived brightness of a point light source in a specific direction (candelas). 900 mcd (0.9 cd) is quite bright for a standard indicator LED. The value is measured on-axis. Due to the 120° viewing angle, the intensity falls off significantly at wider angles.