SMD LED LTST-108TBKT Datasheet - Size 3.2x2.8x1.9mm - Voltage 2.8-3.8V - Power 80mW - Blue InGaN - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a surface-mount device (SMD) Light Emitting Diode (LED). This component is designed for automated printed circuit board (PCB) assembly processes, making it suitable for high-volume manufacturing. Its miniature form factor addresses the needs of space-constrained applications across various electronic sectors.

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 equipment.
• Standardized EIA package outline for design compatibility.
• Input logic compatible, suitable for direct drive from standard digital circuits.
• Designed for compatibility with automatic placement and infrared (IR) reflow soldering processes.
• Preconditioned to JEDEC Moisture Sensitivity Level 3.

1.2 Applications

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

• Telecommunication devices (e.g., cordless phones, cellular phones).
• Office automation equipment (e.g., notebook computers, network systems).
• Consumer home appliances.
• Industrial control and monitoring equipment.
• Indoor signboards and front panel illumination.

2. Technical Parameters: In-Depth Objective Interpretation

The following sections detail the critical electrical, optical, and environmental parameters that define the component's performance and operational limits.

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. All values are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): 80 mW. This is the maximum allowable power loss within the device, primarily as heat from the forward current.
• Peak Forward Current (I_F(PEAK)): 100 mA. This is the maximum instantaneous forward current, permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width).
• DC Forward Current (I_F): 20 mA. This is the recommended maximum continuous forward current for reliable long-term operation.
• Operating Temperature Range (T_opr): -40°C to +85°C. The ambient temperature range over which the device is designed to function.
• Storage Temperature Range (T_stg): -40°C to +100°C. The temperature range for non-operational storage.

2.2 Electro-Optical Characteristics

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

• Luminous Intensity (I_V): 112.0 - 280.0 mcd (millicandela). The perceived brightness of the LED as measured by a sensor filtered to the CIE photopic eye response. The wide range is managed through a binning system.
• Viewing Angle (2θ_1/2): 110° (typical). Defined as the full angle at which the luminous intensity drops to half of its axial (on-axis) value. A 110° angle indicates a wide, diffuse emission pattern suitable for indicator applications.
• Peak Emission Wavelength (λ_p): 468 nm (typical). The wavelength at which the optical output power is maximum.
• Dominant Wavelength (λ_d): 465 - 475 nm. This is the single wavelength perceived by the human eye that defines the color (blue). It is derived from the CIE chromaticity coordinates.
• Spectral Line Half-Width (Δλ): 25 nm (typical). The spectral bandwidth measured at half the maximum intensity (Full Width at Half Maximum - FWHM).
• Forward Voltage (V_F): 2.8 - 3.8 V. The voltage drop across the LED when driven at the specified forward current (20mA).
• Reverse Current (I_R): 10 μA (maximum) at V_R=5V. The device is not designed for reverse bias operation; this parameter is for test purposes only.

3. Binning System Explanation

To ensure color and brightness consistency in production, LEDs are sorted into performance groups or \"bins.\" This allows designers to select components that meet specific application requirements.

3.1 Forward Voltage (V_F) Binning

Units are in Volts at I_F = 20mA. Tolerance within each bin is ±0.10V.

• Bin D7: 2.8V (Min) - 3.0V (Max)
• Bin D8: 3.0V - 3.2V
• Bin D9: 3.2V - 3.4V
• Bin D10: 3.4V - 3.6V
• Bin D11: 3.6V - 3.8V

3.2 Luminous Intensity (I_V) Binning

Units are in millicandela (mcd) at I_F = 20mA. Tolerance within each bin is ±11%.

• Bin R1: 112 mcd - 140 mcd
• Bin R2: 140 mcd - 180 mcd
• Bin S1: 180 mcd - 224 mcd
• Bin S2: 224 mcd - 280 mcd

3.3 Dominant Wavelength (λ_d) Binning

Units are in nanometers (nm) at I_F = 20mA. Tolerance within each bin is ±1nm.

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

4. Performance Curve Analysis

Typical performance curves provide insight into how parameters change with operating conditions. These are essential for robust circuit design.

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

The I-V curve shows the exponential relationship between current and voltage. Operating the LED requires a current-limiting mechanism (e.g., a series resistor or constant current driver) to prevent exceeding the maximum current rating, as small increases in voltage can lead to large increases in current.

4.2 Luminous Intensity vs. Forward Current

This curve typically shows a near-linear relationship between drive current and light output within the recommended operating range. However, efficiency may drop at very high currents due to increased thermal effects.

4.3 Spectral Distribution

The spectral output curve centers around the peak wavelength of 468 nm with a typical half-width of 25 nm, defining the blue color purity.

4.4 Temperature Dependence

Key parameters like forward voltage and luminous intensity are temperature-dependent. Forward voltage typically decreases with increasing junction temperature, while luminous intensity generally decreases. Designers must account for thermal management, especially in high-power or high-ambient-temperature applications.

5. Mechanical and Package Information

5.1 Package Dimensions

The component features a standard SMD package. Critical dimensions include a body size of approximately 3.2mm in length, 2.8mm in width, and a height of 1.9mm. All dimensional tolerances are ±0.2mm unless otherwise noted. The lens color is water clear, and the light source color is InGaN blue.

5.2 Recommended PCB Attachment Pad Layout

A land pattern diagram is provided for designing the PCB footprint. This pattern is optimized for reliable solder joint formation during infrared or vapor phase reflow soldering, ensuring proper mechanical attachment and thermal dissipation.

5.3 Polarity Identification

The cathode is typically indicated by a visual marker on the package, such as a notch, green dot, or cut corner. Correct polarity must be observed during assembly to ensure proper operation.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Profile

A suggested temperature profile compliant with J-STD-020B for lead-free (Pb-free) soldering processes is provided. Key parameters include:

• Pre-heat Temperature: 150-200°C
• Pre-heat Time: Maximum 120 seconds.
• Peak Temperature: Maximum 260°C.
• Time Above Liquidus: As per the provided profile curve.
• Total Soldering Time: Maximum 10 seconds at peak temperature (maximum two reflow cycles allowed).

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

6.2 Hand Soldering

If hand soldering is necessary, use a soldering iron with a temperature not exceeding 300°C. The contact time should be limited to a maximum of 3 seconds, and this should be performed only once.

6.3 Cleaning

If cleaning after soldering is required, use only specified solvents. Immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute is acceptable. Unspecified chemical cleaners may damage the package material.

6.4 Storage and Handling

• Sealed Package: Store at ≤30°C and ≤70% Relative Humidity (RH). The shelf life is one year when stored in the original moisture-proof bag with desiccant.
• Opened Package: For components removed from their moisture-proof bag, the storage ambient should not exceed 30°C and 60% RH. It is recommended to complete IR reflow soldering within 168 hours (7 days) of exposure.
• Extended Exposure: LEDs exposed for more than 168 hours should be baked at approximately 60°C for at least 48 hours prior to solder assembly to remove absorbed moisture and prevent \"popcorning\" during reflow.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The components are supplied in embossed carrier tape with a cover tape.

• Carrier Tape Width: 8mm.
• Reel Diameter: 7 inches (178mm).
• Quantity per Reel: 4000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• The packaging conforms to ANSI/EIA-481 specifications.

8. Application Suggestions and Design Considerations

8.1 Typical Application Circuits

The LED must be driven with a current-limiting device. The simplest method is a series resistor. The resistor value (R_s) can be calculated using Ohm's Law: R_s = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet (e.g., 3.8V) to ensure sufficient current under all conditions. For example, with a 5V supply and a target I_F of 20mA: R_s = (5V - 3.8V) / 0.020A = 60Ω. A 62Ω or 68Ω standard resistor would be suitable. For precision or stability, a constant current driver is recommended.

8.2 Thermal Management

While the power dissipation is low (80mW), effective thermal design on the PCB is still important for longevity and stable performance, especially in high ambient temperatures or enclosed spaces. Ensure the PCB pad design provides adequate thermal relief and consider the overall board layout for heat dissipation.

8.3 Optical Design

The wide 110° viewing angle makes this LED suitable for applications requiring broad visibility. For focused or directed light, secondary optics (lenses, light guides) would be required. The water-clear lens is optimal for true color emission.

9. Technical Comparison and Differentiation

This component belongs to a family of standard SMD LEDs. Its key differentiators include its specific combination of a blue InGaN chip, a wide viewing angle, and its binning structure for V_F, I_V, and λ_d. Compared to non-binned or broadly binned alternatives, it offers designers greater control over color consistency and brightness matching in multi-LED arrays, which is critical for applications like backlighting or status indicators where uniform appearance is required.

10. Frequently Asked Questions (Based on Technical Parameters)

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

Peak Wavelength (λ_p) is the physical wavelength where the LED emits the most optical power. Dominant Wavelength (λ_d) is a calculated value based on human color perception (CIE coordinates) that best represents the color we see. For monochromatic LEDs like this blue one, they are often close, but λ_d is the relevant parameter for color matching.

10.2 Can I drive this LED with a 3.3V supply without a resistor?

No. This is not recommended and is likely to damage the LED. The forward voltage ranges from 2.8V to 3.8V. At 3.3V, an LED with a V_F at the lower end of the range (e.g., 2.9V) would experience an uncontrolled and potentially destructive current surge. Always use a current-limiting mechanism.

10.3 Why is there a 168-hour floor life after opening the moisture barrier bag?

SMD packages can absorb moisture from the atmosphere. During the high-temperature reflow soldering process, this trapped moisture can rapidly vaporize, creating internal pressure that may crack the package (\"popcorning\" or \"delamination\"). The 168-hour limit is the safe exposure time for the specified Moisture Sensitivity Level (MSL 3) before baking is required.

11. Practical Design and Usage Case

Scenario: Designing a multi-indicator status panel for a network router. The panel requires 10 identical blue LEDs to show link activity and power status. To ensure all LEDs appear equally bright and the same shade of blue, the designer should specify tight bin codes when ordering. For example, specifying Bin S1 for intensity (180-224 mcd) and Bin AC for wavelength (465-470 nm) would guarantee visual consistency across the panel. The drive circuit would use a common 5V rail with individual 68Ω series resistors for each LED, calculated based on the maximum V_F to ensure adequate current even for LEDs in the higher voltage bins.

12. Operating Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light through electroluminescence. When a forward voltage is applied across the p-n junction, electrons from the n-type material recombine with holes from the p-type material in the active region. This recombination process releases energy in the form of photons (light). The specific color (wavelength) of the emitted light is determined by the bandgap energy of the semiconductor materials used in the active region. This particular LED utilizes Indium Gallium Nitride (InGaN) as the active material, which is capable of producing high-efficiency light in the blue spectrum.

13. Technology Trends

The development of SMD LEDs continues to focus on several key areas: increased luminous efficacy (more light output per electrical watt), improved color rendering and consistency, further miniaturization of packages, and enhanced reliability under higher temperature and current operating conditions. The use of advanced semiconductor materials like InGaN has been pivotal in achieving high-brightness blue and green LEDs, which are also fundamental for producing white light via phosphor conversion. The trend towards automation and the Internet of Things (IoT) drives demand for reliable, compact, and energy-efficient indicator solutions like this component.