SMD LED LTST-020KFKT Datasheet - 2.0x1.25x1.1mm - 1.8-2.4V - 72mW - Orange AlInGaP - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTST-020KFKT, a surface-mount device (SMD) light-emitting diode (LED). This component belongs to a family of miniature LEDs designed for automated printed circuit board (PCB) assembly and applications where space is a critical constraint. The device utilizes Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor technology to produce an orange light output. Its compact form factor and compatibility with standard industrial processes make it suitable for integration into a wide array of modern electronic equipment.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Packaged in industry-standard 12mm tape on 7-inch diameter reels for automated pick-and-place systems.
• Standard EIA (Electronic Industries Alliance) package outline.
• Integrated circuit (I.C.) compatible logic levels.
• Designed for compatibility with automatic placement and assembly equipment.
• Suitable for use with infrared (IR) reflow soldering processes.
• Preconditioned to accelerate to JEDEC (Joint Electron Device Engineering Council) Moisture Sensitivity Level 3.

1.2 Applications

The LTST-020KFKT is designed for versatile use across multiple sectors. Primary application areas include:

• Telecommunications: Status indicators in routers, modems, and network switches.
• Office Automation: Backlighting for keys and status indicators in printers, scanners, and copiers.
• Consumer Electronics: Power/charge indicators in smartphones, tablets, laptops, and home appliances.
• Industrial Equipment: Panel indicators for machinery, control systems, and instrumentation.
• General Indication: Signal and symbol illumination, front panel backlighting, and general status indication.

2. Package Dimensions and Mechanical Specifications

The LED is housed in a compact, industry-standard 020 package. The key mechanical dimensions are as follows:

• Package Length: 2.0 mm
• Package Width: 1.25 mm
• Package Height: 1.1 mm
• Lead Pitch: 1.05 mm

Lens Color: Water Clear
Emitted Color: Orange (AlInGaP)
Notes: All dimensions are in millimeters. Tolerances are ±0.2mm unless otherwise specified. The package includes polarity marking (typically a cathode indicator) for correct orientation during assembly.

3. Ratings and Characteristics

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

3.1 Absolute Maximum Ratings

• Power Dissipation (Pd): 72 mW
• Peak Forward Current (I_F(peak)): 80 mA (at 1/10 duty cycle, 0.1ms pulse width)
• Continuous Forward Current (I_F): 30 mA DC
• Operating Temperature Range (T_opr): -40°C to +85°C
• Storage Temperature Range (T_stg): -40°C to +100°C

3.2 Electrical and Optical Characteristics

The following table details the typical performance parameters when the device is operated under standard test conditions (I_F = 20mA).

• Luminous Intensity (I_V): 90.0 - 280.0 mcd (millicandela). Measured with a filter approximating the CIE photopic eye response curve.
• Viewing Angle (2θ_1/2): 110 degrees (typical). Defined as the full angle where intensity drops to half its axial value.
• Peak Emission Wavelength (λ_p): 611 nm (typical).
• Dominant Wavelength (λ_d): 600 - 612 nm. Derived from CIE chromaticity coordinates.
• Spectral Line Half-Width (Δλ): 17 nm (typical).
• Forward Voltage (V_F): 1.8 - 2.4 V. Tolerance is ±0.1V.
• Reverse Current (I_R): 10 μA (maximum) at V_R = 5V. Note: This device is not designed for reverse bias operation; this parameter is for infrared test purposes only.

4. Bin Ranking System

To ensure consistency in production and application, LEDs are sorted into performance bins based on key parameters.

4.1 Forward Voltage (V_F) Rank

Binning at I_F = 20mA. Tolerance per bin is ±0.10V.
D2: 1.8V - 2.0V
D3: 2.0V - 2.2V
D4: 2.2V - 2.4V

4.2 Luminous Intensity (I_V) Rank

Binning at I_F = 20mA. Tolerance per bin is ±11%.
Q2: 90 - 112 mcd
R1: 112 - 140 mcd
R2: 140 - 180 mcd
S1: 180 - 220 mcd
S2: 220 - 280 mcd

4.3 Dominant Wavelength (λ_d) Rank

Binning at I_F = 20mA. Tolerance per bin is ±1nm.
P: 600 - 603 nm
Q: 603 - 606 nm
R: 606 - 609 nm
S: 609 - 612 nm

5. Typical Performance Curves and Analysis

Understanding the relationship between operating conditions and performance is crucial for optimal design.

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

The I-V characteristic is non-linear, typical of a diode. The forward voltage (V_F) exhibits a positive temperature coefficient, meaning it decreases slightly as the junction temperature increases for a given current. Designers must account for this when designing current-limiting circuits.

5.2 Luminous Intensity vs. Forward Current

The light output (luminous intensity) is approximately proportional to the forward current in the normal operating range (up to the rated continuous current). However, efficiency may drop at very high currents due to increased thermal effects. Operating consistently above the absolute maximum rating will accelerate lumen depreciation and reduce lifespan.

5.3 Luminous Intensity vs. Ambient Temperature

Like most LEDs, the luminous intensity of the AlInGaP chip decreases as the ambient (and thus junction) temperature rises. This thermal derating must be considered in applications where the LED operates in high-temperature environments or with limited heat sinking. The datasheet provides a curve showing this relationship, which is vital for ensuring consistent brightness under all expected operating conditions.

5.4 Spectral Distribution

The emission spectrum centers around 611 nm (orange). The spectral half-width of approximately 17 nm indicates a relatively pure, monochromatic orange color compared to broader-spectrum sources like phosphor-converted white LEDs. This makes it suitable for applications requiring specific color indication or filtering.

6. Assembly and Handling Guidelines

6.1 Recommended PCB Pad Layout

A land pattern design is provided to ensure reliable soldering and proper alignment. The recommended pad dimensions account for solder fillet formation during reflow. Using the specified pad geometry helps prevent tombstoning (component standing up on one end) and ensures good mechanical and electrical connection.

6.2 Soldering Process

The device is compatible with infrared (IR) reflow soldering processes, including lead-free (Pb-free) soldering. A suggested reflow profile compliant with J-STD-020B is provided, with key parameters including:
Pre-heat Temperature: 150°C - 200°C
Pre-heat Time: Maximum 120 seconds
Peak Reflow Temperature: Maximum 260°C
Time Above Liquidus: As per solder paste specification
Cooling Rate: Controlled to minimize thermal stress.
Note: The actual profile must be characterized for the specific PCB assembly, considering board thickness, component density, and solder paste type.

6.3 Hand Soldering (If Necessary)

If manual repair is required, use a temperature-controlled soldering iron.
Iron Tip Temperature: Maximum 300°C
Soldering Time: Maximum 3 seconds per pad.
Avoid applying mechanical stress to the LED package during or after soldering.

6.4 Cleaning

If post-solder cleaning is required, use only approved solvents. Immerse the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute. Do not use ultrasonic cleaning or unspecified chemical cleaners, as they may damage the epoxy lens or package seals.

6.5 Storage and Moisture Sensitivity

The LEDs are moisture-sensitive (MSL Level 3).
Sealed Bag: Store at ≤ 30°C and ≤ 70% RH. Use within one year of bag seal date.
After Bag Opening: Store at ≤ 30°C and ≤ 60% RH. It is recommended to complete IR reflow within 168 hours (7 days) of exposure to ambient air.
Extended Storage (Opened): Store in a sealed container with desiccant or in a nitrogen desiccator.
Rebaking: Components exposed for more than 168 hours should be baked at approximately 60°C for at least 48 hours prior to soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

7. Packaging and Tape & Reel Specifications

The product is supplied in a tape-and-reel format compatible with high-speed automated assembly equipment.

• Reel Size: Standard 7-inch (178mm) diameter.
• Tape Width: 12 mm.
• Pocket Pitch: 4.0 mm.
• Quantity per Reel: 4,000 pieces (full reel).
• Minimum Order Quantity (MOQ): 500 pieces for remainder reels.
• Cover Tape: Applied to seal components in pockets.
• Packaging Standards: Compliant with ANSI/EIA-481 specifications.
• Missing Components: A maximum of two consecutive empty pockets is allowed per reel specification.

8. Application Notes and Design Considerations

8.1 Current Limiting

An LED is a current-driven device. A series current-limiting resistor is mandatory when driving from a voltage source. The resistor value (R) can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet (2.4V) for a conservative design to ensure the current does not exceed the desired value. For example, to drive at 20mA from a 5V supply: R = (5V - 2.4V) / 0.020A = 130Ω. The nearest standard value (e.g., 120Ω or 150Ω) would be selected, considering power rating (P = I²R).

8.2 Thermal Management

Although small, the LED generates heat at the semiconductor junction. The rated power dissipation (72mW) and operating temperature range (-40°C to +85°C) must be respected. For continuous operation at or near the maximum current (30mA), ensure the PCB provides adequate thermal relief. This can involve using thermal vias under the LED's thermal pad (if applicable), connecting to a copper pour, and avoiding operation in enclosed, unventilated spaces. Excessive junction temperature leads to reduced light output, accelerated aging, and potential premature failure.

8.3 ESD (Electrostatic Discharge) Precautions

While not explicitly rated for ESD immunity in this datasheet, LEDs are generally sensitive to electrostatic discharge. Standard ESD handling precautions should be observed during assembly and handling: use grounded workstations, wrist straps, and conductive containers.

8.4 Optical Design

The 110-degree viewing angle provides a wide, diffuse emission pattern suitable for status indicators meant to be seen from various angles. For applications requiring a more focused beam, secondary optics (lenses or light pipes) would be necessary. The water-clear lens allows the true chip color (orange) to be seen without tinting.

9. Technical Comparison and Selection Guidance

The LTST-020KFKT offers a specific combination of attributes. When selecting an LED for a design, compare the following against alternatives:

• Technology (AlInGaP): Provides high efficiency and good color purity in the orange/red/amber spectrum. It typically has better temperature stability and longer lifetime than older technologies like GaAsP.
• Package Size (020): One of the smallest standard SMD LED packages, ideal for high-density boards. Larger packages (e.g., 0402, 0603) may be easier to handle manually or may offer slightly higher power handling.
• Brightness (90-280mcd): This brightness range is suitable for indoor indicators and backlighting. For sunlight-readable applications or long-distance signaling, higher-intensity LEDs would be required.
• Voltage (1.8-2.4V): The relatively low forward voltage allows operation from low-voltage logic supplies (3.3V, 5V) with minimal voltage drop across the current-limiting resistor, improving power efficiency.

10. Frequently Asked Questions (FAQ)

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

Peak Wavelength (λ_p): The single wavelength at which the emission spectrum has its maximum intensity (611 nm typical for this LED).
Dominant Wavelength (λ_d): The single wavelength of monochromatic light that, when combined with a specified white reference, matches the perceived color of the LED. It is derived from CIE chromaticity coordinates and more closely correlates with the human eye's perception of color (600-612 nm for this LED).

10.2 Can I drive this LED without a current-limiting resistor?

No. Driving an LED directly from a voltage source will cause excessive current to flow, rapidly exceeding the Absolute Maximum Rating for forward current (30mA DC), leading to instantaneous or rapid failure. A series resistor or a constant-current driver circuit is always required.

10.3 How do I interpret the bin codes when ordering?

The full product code (e.g., LTST-020KFKT) may have suffixes indicating specific bins for V_F, I_V, and λ_d. Consult the manufacturer or distributor for available bin combinations. Selecting tighter bins ensures more consistent performance across all units in your production run but may affect cost and availability.

10.4 Is this LED suitable for automotive applications?

This standard datasheet does not list AEC-Q101 automotive qualification. For use in automotive environments (extended temperature ranges, vibration, humidity), an LED specifically qualified to automotive standards should be selected.

11. Practical Design Example

Scenario: Designing a power \"ON\" indicator for a 3.3V microcontroller-based device.
Goal: Provide clear, visible orange indication with a forward current of approximately 15mA (conservative for long life).
Steps:
1. Parameter Selection: From the datasheet, use a typical V_F of 2.1V for calculation. Target I_F = 15mA.
2. Resistor Calculation: R = (V_supply - V_F) / I_F = (3.3V - 2.1V) / 0.015A = 80Ω.
3. Standard Value & Power Check: Select a standard 82Ω resistor. Power dissipation in the resistor: P = I²R = (0.015)² * 82 = 0.01845W. A standard 1/16W (0.0625W) or 1/10W resistor is more than adequate.
4. PCB Layout: Place the 82Ω resistor in series with the LED's anode. Connect the LED's cathode to ground. Follow the recommended pad layout from section 6.1 for the LED. Ensure polarity is correct (cathode mark on PCB silkscreen matches LED marking).
5. Expected Performance: At 15mA, the luminous intensity will be proportionally lower than the 20mA test condition but still sufficient for a panel indicator. The lower current also reduces junction temperature, enhancing long-term reliability.