SMD LED LTST-M140TLKT Datasheet - Blue - 120° Viewing Angle - 3.0V Typ - 102mW - English Technical Document

1. Product Overview

This document details the specifications for a surface-mount device (SMD) light-emitting diode (LED). The component is designed for automated printed circuit board (PCB) assembly processes, featuring a miniature form factor suitable for space-constrained applications. Its primary light source is an indium gallium nitride (InGaN) semiconductor, producing a blue color output through a water-clear lens.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Packaged on 12mm tape within 7-inch diameter reels for automated pick-and-place.
• Standardized EIA (Electronic Industries Alliance) package outline.
• Input compatible with integrated circuit (IC) logic levels.
• Designed for compatibility with automated assembly equipment.
• Suitable for infrared (IR) reflow soldering processes.
• Preconditioned to meet JEDEC (Joint Electron Device Engineering Council) Moisture Sensitivity Level 3.

1.2 Applications

This LED is intended for use as a status indicator, signal light, or for symbol illumination in a wide range of electronic equipment. Typical application fields include:

• Telecommunication devices (e.g., cordless/cellular phones, network systems).
• Office automation equipment (e.g., notebook computers).
• Home appliances.
• Industrial control panels.
• Front panel backlighting.
• Indoor signage.

2. Package Dimensions

The LED conforms to a standard SMD package outline. All critical dimensions, including length, width, height, and pad positions, are provided in the datasheet drawings with a standard tolerance of ±0.2 mm unless otherwise specified. The lens color is water clear, and the light source color is blue (InGaN).

3. Ratings and Characteristics

3.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. They are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): 102 mW
• Peak Forward Current (IFP): 100 mA (at 1/10 duty cycle, 0.1ms pulse width)
• Continuous Forward Current (IF): 30 mA DC
• Operating Temperature Range: -40°C to +85°C
• Storage Temperature Range: -40°C to +100°C

3.2 Suggested IR Reflow Profile

A recommended temperature profile for lead-free solder reflow is provided, aligned with the J-STD-020B standard. The profile includes pre-heat, soak, reflow, and cooling stages, with a peak temperature not exceeding 260°C. Adherence to this profile is critical to prevent thermal damage to the LED package during assembly.

3.3 Electrical and Optical Characteristics

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

• Luminous Flux (Φv): 0.56 lm (Min), 1.40 lm (Max). Measured with a sensor filtered to the CIE photopic eye response.
• Luminous Intensity (Iv): 180 mcd (Min), 450 mcd (Max). Reference value derived from luminous flux.
• Viewing Angle (2θ1/2): 120 degrees (Typical). Defined as the full angle where intensity drops to half its axial value.
• Dominant Wavelength (λd): 448 nm (Min), 458 nm (Max). Represents the perceived color of the blue light.
• Spectral Line Half-Width (Δλ): 25 nm (Typical). Indicates the spectral purity of the blue emission.
• Forward Voltage (VF): 2.6 V (Min), 3.4 V (Max) at IF=20mA.
• Reverse Current (IR): 10 μA (Max) at VR=5V. Note: The device is not designed for reverse bias operation; this parameter is for leakage test reference only.

4. Bin Rank System

The LEDs are sorted into performance bins to ensure consistency. Designers can select bins to meet specific application requirements for brightness, voltage, and color.

4.1 Luminous Flux/Intensity Binning

Bins (S1, S2, T1, T2) define minimum and maximum values for luminous flux and correlated luminous intensity at 20mA.

4.2 Forward Voltage Binning

Bins (D6, D7, D8, D9) define ranges for forward voltage (VF) at 20mA, with a tolerance of ±0.1V per bin. This helps in designing consistent current drive circuits.

4.3 Dominant Wavelength Binning

Bins (AA, AB) define tight ranges for the dominant blue wavelength at 20mA, with a tolerance of ±1nm per bin, ensuring color consistency.

5. Typical Performance Curves

The datasheet includes graphical representations of key relationships:

• Relative Luminous Intensity vs. Forward Current: Shows how light output increases with current, typically in a sub-linear manner at higher currents.
• Forward Voltage vs. Forward Current: Illustrates the diode's I-V characteristic.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the negative temperature coefficient of light output; intensity decreases as junction temperature rises.
• Viewing Angle Pattern: A polar diagram showing the spatial distribution of light intensity.

6. User Guide

6.1 Cleaning

If cleaning is necessary after soldering, only use specified solvents. Immerse the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute. Avoid unspecified chemicals that may damage the epoxy lens or package.

6.2 Recommended PCB Pad Layout

A land pattern design is provided for the surface mount pads. Following this recommendation ensures proper solder joint formation, mechanical stability, and heat dissipation during reflow soldering.

6.3 Tape and Reel Packaging

Detailed dimensions for the carrier tape (pocket size, pitch) and the 7-inch reel are specified. The tape uses a top cover to protect components. Standard reel quantity is 3000 pieces.

7. Cautions and Application Notes

7.1 Intended Use

This LED is designed for general-purpose electronic equipment. It is not rated for safety-critical applications where failure could risk life or health (e.g., aviation, medical life-support). For such uses, consultation with the manufacturer is required.

7.2 Storage Conditions

• Sealed Bag: Store at ≤30°C and ≤70% RH. Use within one year of bag opening.
• After Bag Opening: Store at ≤30°C and ≤60% RH. For components removed from the dry bag, complete IR reflow soldering within 168 hours (MSL Level 3).
• Extended Storage (Opened): Store in a sealed container with desiccant. If stored beyond 168 hours, a bake-out at 60°C for 48 hours is recommended before soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

7.3 Soldering Process

Detailed soldering conditions are provided:

• Reflow Soldering: Follow the JEDEC-compliant profile with pre-heat, peak temperature ≤260°C, and time above liquidus controlled.
• Hand Soldering: If necessary, use a soldering iron at ≤300°C for a maximum of 3 seconds, applied only once.

Adherence to these limits is crucial to prevent thermal degradation of the LED's internal structure and epoxy lens.

8. Design Considerations and Technical Analysis

8.1 Current Driving

The absolute maximum continuous current is 30mA, with a typical operating point of 20mA. To ensure longevity and stable light output, driving the LED with a constant current source is strongly recommended over a constant voltage source. A simple series resistor can be used with a stable voltage supply, but its value must be calculated based on the specific LED's forward voltage bin (VF) and the desired current, accounting for power supply variations.

8.2 Thermal Management

With a maximum power dissipation of 102mW, heat sinking is generally not required for low-duty-cycle indicator use. However, for applications involving high ambient temperatures, continuous operation at maximum current, or multiple LEDs in close proximity, the PCB layout should provide adequate copper area around the LED pads to act as a heat spreader. This helps maintain a lower junction temperature, which is critical for preserving luminous output and operational lifetime.

8.3 Optical Design

The 120-degree viewing angle is quite wide, making this LED suitable for applications requiring broad visibility. For more focused light, secondary optics (e.g., lenses, light pipes) would be necessary. The water-clear lens provides minimal light diffusion, resulting in a more intense, point-like appearance compared to diffused lenses.

8.4 Wavelength and Color Consistency

The tight binning for dominant wavelength (±1nm within AA/AB bins) is a key feature for applications requiring consistent blue color across multiple units, such as in multi-LED displays or backlighting arrays. Designers should specify the required wavelength bin to ensure visual uniformity.

9. Comparison and Selection Guidance

When selecting an SMD LED, key parameters to compare include: luminous intensity/flux (for brightness), viewing angle (for beam spread), forward voltage (for driver design), dominant wavelength (for color), and package size. This particular LED offers a balanced combination of moderate brightness, very wide viewing angle, and standard blue color in a common SMD package, making it a versatile choice for status indication. For higher brightness needs, a device from a higher luminous flux bin (T1, T2) would be selected. For lower power consumption, a device with a lower VF bin (D6, D7) paired with an appropriate current limit resistor would be advantageous.

10. Frequently Asked Questions (FAQs)

Q: Can I drive this LED directly from a 5V logic pin?
A: No. The typical forward voltage is around 3.0V, and a 5V supply would cause excessive current, potentially destroying the LED. You must use a current-limiting resistor or a constant-current driver circuit.

Q: What is the difference between Luminous Flux (lm) and Luminous Intensity (mcd)?
A: Luminous Flux measures the total visible light power emitted in all directions. Luminous Intensity measures the brightness in a specific direction (usually the central axis). This LED's datasheet provides both, with intensity being a derived reference value. The wide 120° angle means the axial intensity (mcd) is lower than a narrow-angle LED with the same total flux (lm).

Q: Why is storage humidity so important?
A>SMD LEDs are moisture-sensitive devices. Absorbed moisture can vaporize rapidly during the high-temperature reflow soldering process, causing internal delamination, cracking, or \"popcorning,\" which leads to failure. The specified storage conditions and floor life (168 hours) prevent this.

Q: Is this LED suitable for outdoor use?
A: The operating temperature range extends to -40°C to +85°C, which covers many outdoor conditions. However, prolonged exposure to direct sunlight (UV), moisture ingress, and thermal cycling beyond the specified limits could degrade the epoxy lens and reduce lifetime. For harsh outdoor environments, LEDs specifically rated for such use should be considered.