SMD LED LTST-T180UBKT Datasheet - Blue 468nm - 120° Viewing Angle - 30mA - 108mW - 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, featuring a miniature form factor ideal for space-constrained applications. The LED utilizes an InGaN (Indium Gallium Nitride) semiconductor material to produce blue light, encapsulated in a water-clear lens package.

1.1 Features and Core Advantages

The LED is compliant with the Restriction of Hazardous Substances (RoHS) directive. It is supplied in industry-standard 8mm tape on 7-inch diameter reels, facilitating compatibility with automated pick-and-place equipment. The device is designed to be integrated circuit (IC) compatible and can withstand standard infrared (IR) reflow soldering processes. It has been preconditioned to accelerate to JEDEC (Joint Electron Device Engineering Council) moisture sensitivity level 3.

1.2 Target Market and Applications

This LED is suitable for a broad spectrum of electronic equipment. Primary application areas include telecommunications devices, office automation equipment, home appliances, and industrial control systems. Its typical uses are as status indicators, signal or symbol luminaries, and for front panel backlighting.

2. Technical Parameters Deep Objective Interpretation

2.1 Absolute Maximum Ratings

All ratings are specified at an ambient temperature (Ta) of 25°C. Exceeding these limits may cause permanent damage.

• Power Dissipation (Pd): 108 mW. This is the maximum amount of power the device can dissipate as heat.
• Peak Forward Current (I_F(PEAK)): 100 mA. This is the maximum allowable instantaneous forward current, typically under pulsed conditions (1/10 duty cycle, 0.1ms pulse width).
• DC Forward Current (I_F): 30 mA. This is the maximum recommended continuous forward current for reliable operation.
• Operating Temperature Range: -40°C to +100°C. The device is guaranteed to function within this ambient temperature range.
• Storage Temperature Range: -40°C to +100°C. The device can be stored without degradation within this range.

2.2 Electrical and Optical Characteristics

These parameters define the typical performance of the LED under normal operating conditions at Ta=25°C.

• Luminous Intensity (I_V): 280 to 560 millicandelas (mcd) at a forward current (I_F) of 20mA. Intensity is measured using a sensor and filter approximating the CIE photopic eye-response curve.
• Viewing Angle (2θ_1/2): 120 degrees (typical). This is the full angle at which the luminous intensity drops to half of its axial (on-axis) value.
• Peak Emission Wavelength (λ_P): 468 nanometers (nm) typical. This is the wavelength at which the spectral power distribution is maximum.
• Dominant Wavelength (λ_d): 465 to 475 nm at I_F=20mA. This is the single wavelength perceived by the human eye, derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): 20 nm typical. This indicates the spectral purity or bandwidth of the emitted light.
• Forward Voltage (V_F): 2.6 to 3.6 Volts at I_F=20mA. This is the voltage drop across the LED when conducting current.
• Reverse Current (I_R): 10 μA maximum at a reverse voltage (V_R) of 5V. The device is not designed for reverse operation; this parameter is for test purposes only.

3. Bin Ranking System Explanation

The LEDs are sorted into bins based on key performance parameters to ensure consistency within a production lot.

3.1 Forward Voltage (V_F) Rank

Measured at 20mA. Tolerance on each bin is ±0.1 Volt.

• D6: 2.6V (Min) - 2.8V (Max)
• D7: 2.8V - 3.0V
• D8: 3.0V - 3.2V
• D9: 3.2V - 3.4V
• D10: 3.4V - 3.6V

3.2 Luminous Intensity (I_V) Rank

Measured in millicandelas (mcd) at 20mA. Tolerance on each bin is ±11%.

• T1: 280 mcd (Min) - 355 mcd (Max)
• T2: 355 mcd - 450 mcd
• U1: 450 mcd - 560 mcd

3.3 Dominant Wavelength (λ_d) Rank

Measured in nanometers (nm) at 20mA. Tolerance for each bin is ±1 nm.

• AC: 465.0 nm (Min) - 470.0 nm (Max)
• AD: 470.0 nm - 475.0 nm

4. Performance Curve Analysis

Typical characteristic curves are provided to illustrate the relationship between key parameters. These curves are essential for circuit design and performance prediction.

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

This curve shows the exponential relationship between the current flowing through the LED and the voltage across it. It is crucial for selecting the appropriate current-limiting resistor in a drive circuit.

4.2 Luminous Intensity vs. Forward Current

This graph demonstrates how the light output (in mcd) increases with forward current. It typically shows a near-linear relationship within the recommended operating range, helping designers achieve desired brightness levels.

4.3 Spectral Power Distribution

This curve plots the relative light intensity against wavelength, showing the peak at approximately 468nm and the spectral half-width of about 20nm, defining the blue color characteristics.

5. Mechanical and Package Information

5.1 Package Dimensions

The LED conforms to an EIA (Electronic Industries Alliance) standard SMD package outline. All dimensions are in millimeters with a general tolerance of ±0.2mm unless otherwise specified. The drawing includes key measurements such as body length, width, height, and lead spacing.

5.2 Recommended PCB Attachment Pad Layout

A land pattern diagram is provided for infrared or vapor phase reflow soldering. This shows the recommended copper pad dimensions and spacing on the PCB to ensure proper solder joint formation, mechanical stability, and thermal management.

5.3 Polarity Identification

The cathode (negative terminal) is typically indicated by a marking on the package, such as a notch, dot, or cut corner. Correct polarity orientation is critical during assembly.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Profile

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

• Pre-heat Temperature: 150°C to 200°C.
• Pre-heat Time: Maximum 120 seconds.
• Peak Temperature: Maximum 260°C.
• Time Above Liquidus: Maximum 10 seconds (maximum two reflow cycles allowed).

Profiles should be characterized for the specific PCB design, components, and solder paste used.

6.2 Storage Conditions

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 original packaging, the storage ambient should not exceed 30°C and 60% RH. It is recommended to complete IR reflow within 168 hours (7 days). For storage beyond this period, bake at approximately 60°C for at least 48 hours before soldering.

6.3 Cleaning

If cleaning is necessary after soldering, use alcohol-based solvents such as ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute. Avoid unspecified chemical liquids.

6.4 Hand Soldering (Soldering Iron)

If hand soldering is required, limit the iron tip temperature to a maximum of 300°C and the soldering time to a maximum of 3 seconds per lead. This should be performed only once.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are packaged in 8mm wide embossed carrier tape wound onto 7-inch (178mm) diameter reels. Each reel contains 5000 pieces. The tape pocket dimensions and reel hub/flange dimensions are provided in detailed drawings, conforming to ANSI/EIA-481 specifications.

7.2 Packing Notes

• Empty component pockets are sealed with a top cover tape.
• The minimum packing quantity for remainder lots is 500 pieces.
• A maximum of two consecutive missing components (lamps) is allowed per reel.

8. Application Suggestions

8.1 Typical Application Circuits

LEDs are current-operated devices. To ensure uniform brightness when driving multiple LEDs in parallel, a current-limiting resistor should be connected in series with each individual LED. A simple drive circuit consists of a voltage source (V_CC), a series resistor (R_S), and the LED. The resistor value is calculated using Ohm's Law: R_S = (V_CC - V_F) / I_F, where V_F is the forward voltage of the LED at the desired current I_F.

8.2 Design Considerations

• Thermal Management: Ensure the PCB design allows for adequate heat dissipation, especially when operating near the maximum current or power ratings.
• Optical Design: The wide 120° viewing angle makes this LED suitable for applications requiring broad illumination or visibility from multiple angles. Consider lensing or light guides if a more focused beam is needed.
• ESD Protection: While not explicitly stated, standard electrostatic discharge (ESD) precautions should be observed during handling and assembly.

9. Technical Comparison and Differentiation

This LED's key differentiators include its combination of a relatively high luminous intensity (up to 560 mcd) with a very wide 120-degree viewing angle. The InGaN technology provides efficient blue light emission. Its compatibility with automated assembly and standard IR reflow processes makes it a cost-effective choice for high-volume manufacturing. The detailed binning structure allows designers to select parts with tight parameter tolerances for applications requiring color or brightness consistency.

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 chart) and represents the single wavelength of the pure spectral color that matches the LED's perceived color. For monochromatic LEDs like this blue one, they are often close but not identical.

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

It is not recommended. The forward voltage (V_F) ranges from 2.6V to 3.6V. Connecting a 3.3V supply directly could result in excessive current if the LED's V_F is lower than 3.3V, potentially damaging it. Always use a series current-limiting resistor or a constant-current driver.

10.3 Why is the storage condition for an opened package stricter than for a sealed one?

The sealed package contains desiccant to maintain a very low humidity level, protecting the moisture-sensitive device. Once opened, the LED is exposed to ambient humidity, which can be absorbed into the plastic package. During reflow soldering, this trapped moisture can rapidly expand, causing internal delamination or \"popcorning,\" which cracks the package. The 168-hour floor life and baking requirements are precautions against this failure mode.

11. Practical Design and Usage Case

Scenario: Designing a multi-LED status indicator panel for a network router.
The panel requires 10 blue status LEDs. Uniform brightness is critical for aesthetic and functional reasons.
Design Steps:
1. Circuit Design: Use a 5V rail. Assuming a typical V_F of 3.2V from the D8 bin and a target I_F of 20mA, calculate the series resistor: R = (5V - 3.2V) / 0.02A = 90 Ohms. A standard 91 Ohm resistor can be used. Place one resistor in series with each LED, connecting all 10 LED-resistor pairs in parallel to the 5V supply.
2. Component Selection: Specify the required bins when ordering: e.g., V_F Bin D8, I_V Bin U1 (for high brightness), λ_d Bin AC for consistent blue hue.
3. PCB Layout: Implement the recommended pad layout from the datasheet. Ensure adequate spacing between LEDs for heat dissipation.
4. Assembly: Follow the IR reflow profile guidelines. If the boards are assembled in batches exceeding the 168-hour floor life for opened components, implement the 60°C/48-hour baking process prior to soldering.

12. Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light when an electric current passes through them. This phenomenon is called electroluminescence. In an InGaN LED, electrical energy causes electrons and holes to recombine within the semiconductor's active region, releasing energy in the form of photons (light). The specific wavelength (color) of the light, in this case blue (~468 nm), is determined by the bandgap energy of the InGaN material. The water-clear epoxy lens serves to protect the semiconductor chip, shape the light output beam (resulting in the 120° viewing angle), and enhance light extraction efficiency.

13. Development Trends

The general trend in SMD LED technology continues towards higher luminous efficacy (more light output per electrical watt), improved color consistency and saturation, and further miniaturization. There is also a focus on enhancing reliability under higher temperature and current density operating conditions. Manufacturing processes are optimized for tighter binning tolerances and higher yields. The drive for energy efficiency and the proliferation of IoT and portable devices ensure sustained demand for reliable, compact, and high-performance indicator LEDs like this component.