SMD LED LTST-M670KRKT Datasheet - AlInGaP Red - Water Clear Lens - 120° Viewing Angle - 30mA Max Current - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a high-brightness, surface-mount LED designed for modern electronic applications. The device utilizes an Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material to produce a vibrant red light output. Encapsulated in a water-clear lens package, this LED is engineered for compatibility with automated assembly processes and standard infrared reflow soldering techniques, making it suitable for high-volume manufacturing.

The core advantages of this component include its compliance with environmental regulations (RoHS), consistent performance across a wide operating temperature range, and packaging that facilitates efficient handling and placement. Its primary target markets include consumer electronics, industrial control panels, automotive interior lighting, and general indicator applications where reliable, bright red illumination is required.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The device is specified for operation under the following absolute maximum conditions, beyond which permanent damage may occur. All values are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation: 72 mW. This is the maximum amount of power the LED can dissipate as heat without exceeding its thermal limits.
• Peak Forward Current: 80 mA. This is permissible only under pulsed conditions with a 1/10 duty cycle and a pulse width of 0.1ms. Exceeding this in DC operation will damage the device.
• DC Forward Current (Continuous): 30 mA. This is the recommended maximum current for continuous, steady-state operation to ensure long-term reliability and maintain specified optical performance.
• Reverse Voltage: 5 V. Applying a reverse bias voltage exceeding this value can cause junction breakdown.
• Operating Temperature Range: -40°C to +85°C. The device is guaranteed to function within its specified parameters across this full industrial temperature range.
• Storage Temperature Range: -40°C to +100°C.

2.2 Electrical & Optical Characteristics

The following table details the key performance parameters under standard test conditions (Ta=25°C, unless otherwise noted). These are the values designers should use for circuit calculations and performance expectations.

• Luminous Intensity (I_V): Ranges from a minimum of 90 mcd to a typical 280 mcd at a forward current (I_F) of 20mA. Intensity is measured using a sensor filtered to match the human eye's photopic response (CIE curve).
• Viewing Angle (2θ_1/2): 120 degrees. This wide viewing angle, defined as the angle where intensity drops to half its on-axis value, makes the LED suitable for applications requiring broad visibility.
• Peak Emission Wavelength (λ_P): 639 nm (typical). This is the wavelength at which the spectral output is strongest.
• Dominant Wavelength (λ_d): 631 nm (typical). Derived from the CIE chromaticity diagram, this single wavelength best represents the perceived color of the LED to the human eye.
• Spectral Line Half-Width (Δλ): 20 nm (typical). This indicates the spectral purity; a smaller value means a more monochromatic light source.
• Forward Voltage (V_F): 2.4V typical, with a range from 2.0V to 2.4V at I_F=20mA. The tolerance on this value is +/- 0.1V. This parameter is crucial for calculating the series current-limiting resistor value.
• Reverse Current (I_R): 10 µA maximum when a reverse voltage (V_R) of 5V is applied.

3. Binning System Explanation

To ensure consistency in brightness across production batches, the luminous intensity of these LEDs is sorted into specific "bins." Each bin defines a guaranteed minimum and maximum intensity range when measured at the standard 20mA test current.

The bin codes for this product are: Q2 (90.0-112.0 mcd), R1 (112.0-140.0 mcd), R2 (140.0-180.0 mcd), S1 (180.0-224.0 mcd), and S2 (224.0-280.0 mcd). A tolerance of +/-11% is applied to each intensity bin. Designers specifying this LED should be aware of which bin they are using, as it directly impacts the achieved brightness in the final application. For critical applications requiring uniform appearance, LEDs from the same bin code should be used.

4. Performance Curve Analysis

While specific graphical curves are referenced in the source document, their implications are critical for design. Key relationships that would be shown in such curves include:

• I-V (Current-Voltage) Curve: Shows the exponential relationship between forward voltage and current. The curve will have a distinct "knee" voltage (around 2.0-2.4V) above which current increases rapidly with small voltage increases. This highlights why LEDs must be driven with a current source or a voltage source with a series resistor.
• Luminous Intensity vs. Forward Current: Typically shows a near-linear relationship between drive current and light output within the recommended operating range. Driving the LED above its maximum DC current may lead to super-linear increase in heat and efficiency roll-off.
• Luminous Intensity vs. Ambient Temperature: For AlInGaP LEDs, light output generally decreases as ambient temperature increases. Understanding this derating is essential for applications operating at high temperatures to ensure sufficient brightness is maintained.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing a peak at approximately 639 nm with a characteristic width (half-width) of about 20 nm.

5. Mechanical & Package Information

5.1 Device Dimensions

The LED conforms to a standard EIA surface-mount package outline. All critical dimensions for PCB footprint design—including body length, width, height, and lead spacing—are provided in the source document with a standard tolerance of ±0.2 mm. The package features a water-clear lens material.

5.2 PCB Land Pattern Design

A recommended printed circuit board (PCB) attachment pad layout is provided to ensure reliable soldering and proper mechanical alignment. This land pattern is optimized for both infrared and vapor phase reflow soldering processes. Adhering to this recommended footprint is crucial for achieving good solder joint formation, thermal management, and preventing tombstoning during reflow.

5.3 Polarity Identification

The cathode (negative terminal) is typically identified by a visual marker on the LED package, such as a notch, a green dot, or a cut corner on the lens or body. The anode (positive terminal) is the other lead. Correct polarity must be observed during assembly, as applying reverse bias can damage the device.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Parameters

The component is compatible with lead-free (Pb-free) infrared reflow soldering processes. A suggested profile, compliant with JEDEC standard J-STD-020B, is provided. Key parameters include:

• Pre-heat Temperature: 150-200°C
• Pre-heat Time: Maximum 120 seconds.
• Peak Body Temperature: Maximum 260°C.
• Time Above Liquidus: Recommended to follow solder paste manufacturer specifications, typically 60-90 seconds.

It is emphasized that the optimal profile depends on the specific PCB design, solder paste, and oven used. Characterization for the specific application is recommended.

6.2 Hand Soldering Notes

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

• Soldering Iron Temperature: Maximum 300°C.
• Soldering Time per Lead: Maximum 3 seconds.
• Number of Times: Soldering should be attempted only once per joint to avoid thermal stress on the plastic package.

6.3 Storage & Handling Conditions

Moisture sensitivity is a critical factor for surface-mount devices. This LED is packaged in a moisture-barrier bag with desiccant.

• Sealed Package Storage: ≤ 30°C and ≤ 70% Relative Humidity (RH). Shelf life is one year from the date code.
• After Opening Package: The "floor life" is 168 hours (7 days) when stored at ≤ 30°C and ≤ 60% RH. If exposed for longer, the LEDs must be baked at approximately 60°C for at least 48 hours before soldering to remove absorbed moisture and prevent "popcorning" during reflow.
• Long-Term Open Storage: Should be in a sealed container with desiccant or in a nitrogen-purged desiccator.

6.4 Cleaning

If post-solder cleaning is required, 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 plastic package or lens.

7. Packaging & Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied on embossed carrier tape for automated pick-and-place machines.

• Tape Width: 8 mm.
• Reel Diameter: 7 inches (178 mm).
• Quantity per Reel: 2000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Packing Standard: Complies with EIA-481-1-B specifications. The tape has a cover seal, and a maximum of two consecutive empty component pockets is allowed.

8. Application Design Recommendations

8.1 Typical Application Circuits

LEDs are current-driven devices. The most reliable and recommended drive method is to use a series current-limiting resistor for each LED, even when multiple LEDs are connected in parallel to a voltage source (Circuit Model A). This compensates for the natural variation in forward voltage (V_F) from one LED to another, ensuring uniform current and therefore uniform brightness across all devices. Driving multiple LEDs in parallel without individual resistors (Circuit Model B) is discouraged, as the LED with the lowest V_F will draw disproportionately more current, leading to uneven brightness and potential overstress.

The series resistor value (R_s) is calculated using Ohm's Law: R_s = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet for a conservative design that guarantees the current does not exceed the desired I_F.

8.2 Design Considerations

• Thermal Management: While power dissipation is low, maintaining the junction temperature within limits is key to long life. Ensure adequate copper area on the PCB pads to act as a heat sink, especially when operating at high ambient temperatures or near maximum current.
• ESD Protection: Although not explicitly stated as highly sensitive, standard ESD handling precautions should be observed during assembly.
• Application Scope: This component is intended for standard electronic equipment. For applications requiring exceptional reliability or where failure could risk safety (e.g., aviation, medical life-support), additional qualification and consultation with the manufacturer are necessary.

9. Technical Comparison & Differentiation

Compared to older technologies like GaAsP (Gallium Arsenide Phosphide) red LEDs, this AlInGaP-based device offers significantly higher luminous efficiency, resulting in greater brightness for the same drive current. The water-clear lens, as opposed to a diffused or colored lens, provides the highest possible light extraction and a more focused, intense beam pattern suitable for applications requiring a sharp, bright point of light. The 120-degree viewing angle offers a good balance between on-axis intensity and off-axis visibility. Its compatibility with standard IR reflow processes differentiates it from LEDs that may require manual soldering or wave soldering.

10. Frequently Asked Questions (FAQs)

Q: Can I drive this LED at 30mA continuously?

A: Yes, 30mA is the maximum recommended DC forward current. For optimal longevity and to account for temperature effects, designing for a lower current (e.g., 20mA) is often advisable.

Q: What is the difference between Peak Wavelength and Dominant Wavelength?

A: Peak Wavelength (639 nm) is the physical peak of the light spectrum emitted. Dominant Wavelength (631 nm) is a calculated value that represents the single wavelength of pure monochromatic light that would appear to have the same color to the human eye. Dominant wavelength is more relevant for color specification.

Q: Why is a series resistor necessary even with a constant voltage supply?

A: The forward voltage of an LED has a tolerance and decreases with increasing temperature. A series resistor provides negative feedback: if current tries to increase (e.g., due to a low V_F part or temperature rise), the voltage drop across the resistor increases, limiting the current rise and stabilizing the LED's operation.

Q: How do I interpret the bin code on my order?

A: The bin code (e.g., S1) specifies the guaranteed range of luminous intensity for that batch of LEDs. Always check the bin code against the table in section 3 to understand the minimum brightness you can expect in your design.

11. Practical Application Examples

Example 1: Status Indicator Panel: An industrial control unit uses an array of these LEDs as fault and status indicators on a front panel. The wide 120° viewing angle ensures the indicators are visible to operators from various positions. The designer uses the S2 bin for high brightness and calculates a series resistor for a 20mA drive current from a 5V rail: R = (5V - 2.4V) / 0.02A = 130 Ohms (a standard 130 or 150 Ohm resistor is selected). The PCB layout follows the recommended pad pattern to ensure automatic placement and good solder joints.

Example 2: Backlighting for Membrane Switches: The LED is placed behind a translucent graphic on a membrane keypad. The water-clear lens and high intensity provide a crisp, evenly illuminated symbol. In this case, the LED might be driven at a lower current (e.g., 10mA) to achieve the desired backlighting level while minimizing power consumption and heat within the sealed switch assembly.

12. Technology Principle Introduction

This LED is based on Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor technology. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the active region where they recombine. The energy released during this recombination is emitted as photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy of the semiconductor, which directly dictates the wavelength (color) of the emitted light—in this case, red. The water-clear epoxy lens serves to protect the semiconductor die, shape the light output beam, and enhance light extraction from the chip.

13. Industry Trends & Developments

The general trend in LED technology is toward ever-higher efficiency (more lumens per watt), improved color consistency, and lower cost. For indicator-type LEDs like this one, miniaturization continues while maintaining or increasing brightness. There is also a growing emphasis on broader and more precise operating temperature ranges for automotive and industrial applications. The move to lead-free and halogen-free materials for environmental compliance is now standard. Future developments may include integrated driver circuitry within the package or enhanced packaging for better thermal performance at higher drive currents.