SMD LED LTST-C150TBKT-5A Datasheet - Blue InGaN - 5mA - 45mcd - English Technical Document

1. Product Overview

This document provides the technical specifications for a surface-mount device (SMD) light-emitting diode (LED). The device utilizes an Indium Gallium Nitride (InGaN) semiconductor chip to produce blue light. It is designed for automated assembly processes and is packaged on tape and reel for high-volume production.

The core advantages of this component include its compatibility with infrared reflow soldering processes, suitability for use with automatic placement equipment, and its classification as a RoHS-compliant green product. Its primary target market includes consumer electronics, indicator lights, backlighting applications, and general-purpose illumination where a compact, reliable blue light source is required.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The device must not be operated beyond these limits to prevent permanent damage.

• Power Dissipation: 76 mW. This is the maximum power the LED package can dissipate as heat under specified conditions.
• Peak Forward Current: 100 mA. This is the maximum instantaneous current, permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width).
• DC Forward Current: 20 mA. This is the maximum continuous forward current recommended for reliable long-term operation.
• Operating Temperature Range: -20°C to +80°C. The ambient temperature range within which the LED is designed to function correctly.
• Storage Temperature Range: -30°C to +100°C. The temperature range for non-operational storage.
• Infrared Soldering Condition: 260°C for 10 seconds. The maximum thermal profile the component can withstand during reflow soldering.

2.2 Electrical and Optical Characteristics

These parameters are measured at an ambient temperature (Ta) of 25°C and define the typical performance.

• Luminous Intensity (I_V): 11.2 - 45.0 mcd (min - max) at a forward current (I_F) of 5mA. This measures the perceived brightness of the light output.
• Viewing Angle (2θ_1/2): 130 degrees (typical). This is the full angle at which the luminous intensity drops to half of its peak value, indicating a wide viewing pattern.
• Peak Emission Wavelength (λ_P): 468 nm (typical). The wavelength at which the spectral power distribution is maximum.
• Dominant Wavelength (λ_d): 465.0 - 475.0 nm at I_F=5mA. This is the single wavelength that best represents the perceived color of the light.
• Spectral Line Half-Width (Δλ): 25 nm (typical). A measure of the spectral purity; a smaller value indicates a more monochromatic light source.
• Forward Voltage (V_F): 2.65 - 3.05 V (min - max) at I_F=5mA. The voltage drop across the LED when conducting current.
• Reverse Current (I_R): 10 μA (max) at a reverse voltage (V_R) of 5V. The small leakage current when the LED is reverse-biased. The device is not designed for reverse operation.

3. Binning System Explanation

To ensure consistency in production, LEDs are sorted into bins based on key parameters. This allows designers to select components that meet specific tolerance requirements for their application.

3.1 Forward Voltage Binning

Units are sorted into four bins (1-4) based on their forward voltage at 5mA, each with a range of 0.1V. Tolerance on each bin is ±0.1V.

• Bin 1: 2.65V - 2.75V
• Bin 2: 2.75V - 2.85V
• Bin 3: 2.85V - 2.95V
• Bin 4: 2.95V - 3.05V

3.2 Luminous Intensity Binning

Units are sorted into six bins (L1, L2, M1, M2, N1, N2) based on luminous intensity at 5mA. Tolerance on each bin is ±15%.

• L1: 11.2 - 14.0 mcd
• L2: 14.0 - 18.0 mcd
• M1: 18.0 - 22.4 mcd
• M2: 22.4 - 28.0 mcd
• N1: 28.0 - 35.5 mcd
• N2: 35.5 - 45.0 mcd

3.3 Dominant Wavelength Binning

Units are sorted into two bins (AC, AD) based on dominant wavelength at 5mA. Tolerance for each bin is ±1 nm.

• AC: 465.0 - 470.0 nm
• AD: 470.0 - 475.0 nm

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Figure 1 for spectral distribution, Figure 5 for viewing angle), their typical interpretations are crucial for design.

4.1 Current vs. Voltage (I-V) Characteristic

The forward voltage (V_F) exhibits a logarithmic relationship with forward current (I_F). It is non-linear, with a threshold voltage (around 2.6-2.8V for blue InGaN) below which very little current flows. Beyond this threshold, small increases in voltage cause large increases in current. Therefore, LEDs are typically driven with a constant current source, not a constant voltage, to ensure stable light output and prevent thermal runaway.

4.2 Luminous Intensity vs. Current (L-I) Characteristic

The light output (luminous intensity) is generally proportional to the forward current over a significant range. However, efficiency (lumens per watt) may peak at a certain current and then decrease at higher currents due to increased heat generation and other non-radiative recombination processes within the semiconductor.

4.3 Temperature Dependence

LED performance is temperature-sensitive. Typically, as the junction temperature increases:

• Forward Voltage (V_F): Decreases. This has implications for constant-voltage driving circuits.
• Luminous Intensity/Flux: Decreases. Higher temperatures reduce the internal quantum efficiency.
• Dominant Wavelength: May shift slightly, usually towards longer wavelengths (red-shift), which can affect color perception in precision applications.

Effective thermal management is critical for maintaining performance and longevity.

5. Mechanical and Package Information

5.1 Package Dimensions

The device conforms to an EIA standard package outline. All dimensions are provided in millimeters, with a general tolerance of ±0.10 mm unless otherwise specified. The package features a water-clear lens, which is optimal for the blue InGaN chip as it does not alter the color output (unlike a diffused or tinted lens).

5.2 Polarity Identification

Polarity is a critical aspect of LED installation. The datasheet includes a diagram showing the cathode and anode markings on the component. Typically, the cathode is indicated by a green marking, a notch, or a shorter lead/tab. Incorrect polarity will prevent the LED from illuminating and applying significant reverse voltage can damage the device.

5.3 Suggested Soldering Pad Layout

A recommended land pattern (footprint) for the printed circuit board (PCB) is provided. Adhering to these dimensions ensures proper solder joint formation, alignment, and mechanical stability during and after the reflow process. The pad design also influences the thermal path for heat dissipation away from the LED junction.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

A suggested infrared (IR) reflow profile for lead-free (Pb-free) solder processes is provided. Key parameters include:

• Pre-heat: 150-200°C for a maximum of 120 seconds to gradually heat the board and activate the flux.
• Peak Temperature: Maximum of 260°C.
• Time Above Liquidus: The time the solder joints spend above the melting point of the solder paste is critical for proper wetting. The profile on page 3 of the datasheet provides a visual reference compliant with JEDEC standards.
• Cooling Rate: Controlled cooling is recommended to minimize thermal stress on the component and board.

It is emphasized that the optimal profile depends on the specific board design, components, solder paste, and oven, so characterization is necessary.

6.2 Hand Soldering

If hand soldering is necessary, extreme care must be taken:

• Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per joint.
• Limit: Hand soldering should be performed only once to avoid thermal damage to the plastic package and the semiconductor die.

6.3 Cleaning

If cleaning is required 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 recommended. The use of unspecified chemicals can damage the plastic package material or the lens.

6.4 Storage and Handling

• ESD Precautions: LEDs are sensitive to electrostatic discharge (ESD). Handling with wrist straps, anti-static gloves, and on properly grounded equipment is mandatory.
• Moisture Sensitivity: The package is moisture-sensitive. Once the original sealed moisture-proof bag (with desiccant) is opened, the components should be used within one week if stored at ≤30°C and ≤60% RH. For longer storage out of the original bag, storage in a sealed container with desiccant or in a nitrogen ambient is required. Components stored for more than one week outside the original packaging should be baked (e.g., at 60°C for 20 hours) before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The device is supplied in industry-standard packaging for automated assembly:

• Reel Size: 7-inch diameter.
• Quantity per Reel: 3000 pieces.
• Minimum Order Quantity: 500 pieces for remainder quantities.
• Tape Specifications: Compliant with ANSI/EIA 481-1-A-1994. Empty component pockets are sealed with a top cover tape.
• Missing Components: The maximum number of consecutive missing components ("missing lamps") in the tape is two.

8. Application Notes and Design Considerations

8.1 Typical Application Scenarios

• Status Indicators: Power, connectivity, or operational status lights on consumer electronics, appliances, and industrial equipment.
• Backlighting: For small LCD displays, keypads, or decorative panels.
• Decorative Lighting: In signage, accent lighting, or consumer gadgets.
• Sensor Systems: As a light source for optical sensors or interrupters.

Important Notice: The datasheet specifies that these LEDs are intended for ordinary electronic equipment. Applications requiring exceptional reliability, particularly where failure could jeopardize life or health (e.g., aviation, medical devices, safety systems), require prior consultation and approval.

8.2 Circuit Design Considerations

• Current Limiting: Always use a series current-limiting resistor or a dedicated constant-current LED driver IC. The value is calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet to ensure the current does not exceed the limit even with part-to-part variation.
• Power Dissipation: Ensure the calculated power (P = V_F * I_F) does not exceed the absolute maximum rating of 76 mW, considering the worst-case V_F and ambient temperature.
• Reverse Voltage Protection: If there is any possibility of a reverse voltage being applied (e.g., in AC circuits or with inductive loads), a protection diode should be placed in parallel with the LED (cathode to anode) to clamp the reverse voltage.
• Thermal Management: For designs operating at high currents or in high ambient temperatures, ensure the PCB provides adequate thermal relief. Copper pads connected to ground/power planes can help dissipate heat.

9. Technology Introduction and Operating Principle

This LED is based on an Indium Gallium Nitride (InGaN) semiconductor chip. InGaN is a direct bandgap semiconductor material whose bandgap energy can be tuned by varying the ratio of Indium to Gallium. For blue LEDs, a specific composition is used that results in a bandgap corresponding to photon emission in the blue wavelength range (around 465-475 nm).

When a forward voltage is applied, electrons and holes are injected into the active region of the semiconductor. They recombine radiatively, releasing energy in the form of photons (light). The water-clear epoxy package acts as a lens, shaping the light output and providing environmental protection for the delicate semiconductor chip and wire bonds.

10. Frequently Asked Questions (FAQ)

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

Peak Wavelength (λ_P): The single wavelength where the spectral power output is highest. It is a physical measurement.
Dominant Wavelength (λ_d): The single wavelength that best matches the perceived color of the light as defined by the human eye's response (CIE chromaticity diagram). For monochromatic sources like blue LEDs, they are often very close, but dominant wavelength is more relevant for color perception.

10.2 Can I drive this LED at 20mA continuously?

Yes, 20mA is the maximum recommended DC forward current. However, for longest lifetime and highest efficiency, driving it at a lower current (e.g., 5mA as used for testing) is often sufficient for indicator applications and generates less heat.

10.3 Why is there a binning system?

Manufacturing variations cause slight differences in V_F, intensity, and wavelength between individual LEDs. Binning sorts them into groups with tightly controlled parameters. This allows designers to select bins that ensure consistent brightness and color across all units in their product, which is critical for multi-LED arrays or applications with strict color requirements.

10.4 How do I interpret the viewing angle?

A viewing angle of 130 degrees (2θ_1/2) means the angle from the center axis where the brightness falls to 50% of the on-axis value is 65 degrees. Therefore, the total angular width of the beam at half-power is 130 degrees. This indicates a very wide, diffuse light pattern suitable for wide-area illumination or indicators that need to be seen from many angles.