SMD LED LTST-C171KDKT Datasheet - Red AllnGaP - 20mA - 50mW - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a surface-mount device (SMD) LED lamp. Designed for automated printed circuit board (PCB) assembly, this component is suitable for space-constrained applications across a wide range of electronic equipment.

1.1 Key Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Utilizes an ultra-bright Aluminum Indium Gallium Phosphide (AllnGaP) semiconductor chip for red light emission.
• Supplied in industry-standard 8mm tape on 7-inch diameter reels for automated pick-and-place machinery.
• Packaged in an EIA (Electronic Industries Alliance) standard form factor.
• Electrically compatible with integrated circuit (IC) drive levels.
• Designed for compatibility with automatic placement equipment.
• Withstands standard infrared (IR) reflow soldering processes.

1.2 Target Applications

This LED is intended for use as a status indicator, backlight, or signal source in various sectors:

• Telecommunications equipment (e.g., cordless/cellular phones).
• Office automation devices (e.g., notebook computers, network systems).
• Home appliances and consumer electronics.
• Industrial control and instrumentation panels.
• Keypad or keyboard backlighting.
• Status and power indicators.
• Micro-displays and symbolic luminaries.

2. Package Dimensions and Configuration

The device features a water-clear lens encapsulating a red AllnGaP light source. All dimensional specifications are provided in millimeters (mm). Unless explicitly stated otherwise, the standard tolerance for all linear dimensions is ±0.1 mm. Detailed mechanical drawings defining the package outline, lead configuration, and recommended PCB footprint are included in the datasheet to ensure proper board layout and soldering.

3. Ratings and Characteristics

All specifications are defined at an ambient temperature (Ta) of 25°C unless otherwise noted. Exceeding the Absolute Maximum Ratings may cause permanent device damage.

3.1 Absolute Maximum Ratings

• Power Dissipation (Pd): 50 mW
• Peak Forward Current (I_F(peak)): 40 mA (at 1/10 duty cycle, 0.1ms pulse width)
• Continuous DC Forward Current (I_F): 20 mA
• Reverse Voltage (V_R): 5 V
• Operating Temperature Range: -30°C to +85°C
• Storage Temperature Range: -40°C to +85°C
• Infrared Reflow Soldering Condition: 260°C peak temperature for a maximum of 10 seconds.

3.2 Electrical and Optical Characteristics

The following table details the typical performance parameters when the device is operated at its nominal forward current of 20mA.

• Luminous Intensity (I_V): 4.5 - 45.0 mcd (millicandela). Measured using a sensor filtered to match the CIE photopic eye response curve.
• Viewing Angle (2θ_1/2): 130 degrees. Defined as the full angle where intensity drops to half its on-axis value.
• Peak Emission Wavelength (λ_P): 650 nm (typical).
• Dominant Wavelength (λ_d): 630 - 645 nm. Represents the perceived color point on the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): 20 nm (typical). The wavelength band at half the peak spectral intensity.
• Forward Voltage (V_F): 1.6 - 2.4 V at I_F=20mA.
• Reverse Current (I_R): 10 μA (maximum) at V_R=5V.

3.3 Electrostatic Discharge (ESD) Caution

This device is sensitive to electrostatic discharge and electrical surges. Proper ESD control procedures must be followed during handling and assembly. This includes the use of grounded wrist straps, anti-static gloves, and ensuring all equipment and work surfaces are properly grounded to prevent latent or catastrophic damage.

4. Bin Ranking System

To ensure color and brightness consistency in production, devices are sorted into bins based on measured luminous intensity. The bin code is marked for traceability.

4.1 Luminous Intensity Binning

For the red color variant, bins are defined as follows (measured at I_F=20mA):

• Bin J: 4.5 - 7.1 mcd
• Bin K: 7.1 - 11.2 mcd
• Bin L: 11.2 - 18.0 mcd
• Bin M: 18.0 - 28.0 mcd
• Bin N: 28.0 - 45.0 mcd

A tolerance of ±15% applies to the limits of each intensity bin.

5. Performance Curve Analysis

The datasheet includes graphical representations of key characteristics, which are essential for circuit design and performance prediction.

5.1 Current vs. Voltage (I-V) Curve

This curve illustrates the relationship between forward voltage (V_F) and forward current (I_F). It shows the typical turn-on voltage and the dynamic resistance of the LED, which is crucial for designing current-limiting circuitry.

5.2 Relative Luminous Intensity vs. Forward Current

This graph shows how light output scales with drive current. It typically demonstrates a near-linear relationship within the recommended operating range, aiding in brightness control through current modulation.

5.3 Relative Luminous Intensity vs. Ambient Temperature

This curve depicts the thermal derating of light output. Luminous intensity generally decreases as the junction temperature rises, which is a critical factor for applications operating in elevated temperature environments or at high drive currents.

5.4 Spectral Distribution

The spectral power distribution plot shows the intensity of emitted light as a function of wavelength. It confirms the peak wavelength (λ_P) and spectral half-width (Δλ), defining the color purity of the red emission.

6. Assembly and Handling Guidelines

6.1 Cleaning

If cleaning is necessary after soldering, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute is acceptable. Unspecified chemical cleaners may damage the epoxy lens or package.

6.2 Recommended PCB Pad Layout

A detailed drawing of the suggested solder pad geometry is provided to ensure reliable solder joint formation, proper alignment, and sufficient mechanical strength. Adhering to this footprint is vital for successful reflow soldering.

6.3 Tape and Reel Packaging Specifications

The device is supplied in embossed carrier tape with a protective cover tape. Key packaging details include:

• Carrier tape width: 8 mm.
• Reel diameter: 7 inches (178 mm).
• Quantity per reel: 3000 pieces.
• Minimum order quantity for remnants: 500 pieces.
• Packaging conforms to ANSI/EIA-481 standards.

7. Application Notes and Cautions

7.1 Intended Use

This component is designed for standard commercial and industrial electronic equipment. It is not rated 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 is required.

7.2 Storage Conditions

• Sealed Package: Store at ≤30°C and ≤90% Relative Humidity (RH). Shelf life is one year when the moisture barrier bag with desiccant is intact.
• Opened Package: For components removed from their sealed bag, the storage environment must not exceed 30°C / 60% RH. It is recommended to complete IR reflow soldering within 672 hours (28 days) of exposure, corresponding to Moisture Sensitivity Level (MSL) 2a. For longer exposure, baking at approximately 60°C for at least 20 hours is required before soldering to prevent popcorning during reflow.

7.3 Soldering Recommendations

Reflow Soldering (Pb-Free Process):

• Pre-heat Temperature: 150-200°C
• Pre-heat Time: Maximum 120 seconds
• Peak Body Temperature: Maximum 260°C
• Time Above 260°C: Maximum 10 seconds total (max. 2 reflow cycles)

Hand Soldering (Soldering Iron):

• Iron Tip Temperature: Maximum 300°C
• Contact Time: Maximum 3 seconds (one time only)

Note: The optimal reflow profile depends on the specific PCB design, solder paste, and oven. The provided conditions are guidelines based on JEDEC standards and component-level verification.

7.4 Drive Circuit Design

LEDs are current-operated devices. To ensure uniform brightness when driving multiple LEDs in parallel, a individual current-limiting resistor must be placed in series with each LED. This compensates for the natural variation in forward voltage (V_F) from device to device, preventing current hogging and uneven illumination. Driving LEDs directly from a voltage source without series resistance is not recommended and will likely lead to premature failure.

8. Technical Deep Dive and Design Considerations

8.1 AllnGaP Technology

Aluminum Indium Gallium Phosphide (AllnGaP) is a semiconductor material system particularly well-suited for producing high-efficiency red, orange, and yellow LEDs. Compared to older technologies like Gallium Arsenide Phosphide (GaAsP), AllnGaP offers significantly higher luminous efficacy (light output per electrical watt), better temperature stability, and superior color purity. This makes it the preferred choice for applications requiring bright, reliable red indicators.

8.2 Thermal Management

While the package is small, managing junction temperature is critical for long-term reliability and maintaining light output. The 50mW maximum power dissipation rating must be respected. Designers should consider the thermal path from the LED junction to the ambient environment. Using an adequate copper pad area on the PCB acts as a heat sink, helping to dissipate heat and lower the operating junction temperature, thereby preserving luminous intensity and lifespan.

8.3 Optical Design Considerations

The 130-degree viewing angle classifies this as a wide-angle LED. This is ideal for status indicators that need to be visible from a broad range of perspectives. For applications requiring a more focused beam, secondary optics (like lenses or light pipes) would be necessary. The water-clear lens provides the highest possible light extraction from the chip, maximizing forward luminous intensity.

8.4 Comparison with Alternative Technologies

The primary advantage of this AllnGaP red LED is its combination of brightness and efficiency. For less demanding applications where ultimate brightness is not required, older GaAsP LEDs might be a lower-cost alternative, but they would be dimmer and less efficient. For applications requiring deep red or infrared emission, Gallium Arsenide (GaAs) or Aluminum Gallium Arsenide (AlGaAs) chips might be used. The choice depends on the specific wavelength, efficiency, and cost targets of the application.