SMD LED LTST-C990NSKT-PO Datasheet - Yellow AlInGaP - 25mA - 62.5mW - English Technical Document

1. Product Overview

This document details the specifications for a high-performance, surface-mount LED designed for automated assembly and space-constrained applications. The device utilizes an Ultra Bright AlInGaP chip to deliver a vibrant yellow light output, making it suitable for a wide range of modern electronic equipment.

1.1 Features

• Compliant with RoHS environmental standards.
• Features a dome lens for optimized light distribution.
• Utilizes an Ultra Bright Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor chip.
• Supplied in industry-standard 8mm tape on 7-inch diameter reels for automated pick-and-place.
• Package conforms to EIA (Electronic Industries Alliance) standards.
• Logic-level compatible drive current.
• Fully compatible with automated placement and assembly equipment.
• Withstands standard infrared (IR) reflow soldering processes.

1.2 Applications

This LED is engineered for integration into various electronic systems, including but not limited to:

• Telecommunication devices and office automation equipment.
• Home appliances and industrial control panels.
• Backlighting for keypads and keyboards.
• Status and power indicators.
• Micro-displays and compact informational panels.
• Signal lighting and symbolic luminaries.

2. Technical Parameters: In-Depth Objective Interpretation

2.1 Absolute Maximum Ratings

The following limits must not be exceeded under any conditions, as doing so may cause permanent damage to the device. All ratings are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): 62.5 mW. This is the maximum total power the package can dissipate as heat.
• Peak Forward Current (I_F(PEAK)): 60 mA. Permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width).
• Continuous Forward Current (I_F): 25 mA DC. The recommended maximum current for continuous operation.
• Reverse Voltage (V_R): 5 V. Exceeding this voltage in reverse bias can break down the LED junction.
• Operating Temperature Range: -30°C to +85°C.
• Storage Temperature Range: -40°C to +85°C.
• Infrared Reflow Soldering Condition: Withstand 260°C peak temperature for a maximum of 10 seconds.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured at Ta=25°C and I_F=20mA, unless otherwise noted. They define the operational behavior of the LED.

• Luminous Intensity (I_V): 710.0 to 1800.0 mcd (millicandela). Measured using a sensor filtered to match the CIE photopic eye response curve. The wide range is managed by the binning system.
• Viewing Angle (2θ_1/2): 75 degrees. This is the full angle at which the luminous intensity drops to half of its peak axial value, indicating a relatively wide viewing cone typical of dome lens packages.
• Peak Emission Wavelength (λ_P): Typically 591 nm. The wavelength at which the spectral power distribution is maximum.
• Dominant Wavelength (λ_d): 587.0 to 597.0 nm. This is the single wavelength perceived by the human eye that defines the yellow color of the LED, derived from the CIE chromaticity coordinates.
• Spectral Line Half-Width (Δλ): Typically 15 nm. The bandwidth of the emitted light spectrum at half its maximum intensity, indicating color purity.
• Forward Voltage (V_F): 1.7 to 2.5 V. The voltage drop across the LED when driven at 20mA.
• Reverse Current (I_R): Maximum 10 µA when a reverse bias of 5V is applied.

3. Binning System Explanation

To ensure consistent performance in production, LEDs are sorted into bins based on key parameters. This allows designers to select parts that meet specific application requirements for brightness, color, and voltage.

3.1 Forward Voltage (V_F) Binning

Bins define the range of forward voltage drop at 20mA. Tolerance within each bin is ±0.1V.

• E2: 1.7V – 1.9V
• E3: 1.9V – 2.1V
• E4: 2.1V – 2.3V
• E5: 2.3V – 2.5V

3.2 Luminous Intensity (I_V) Binning

Bins categorize the minimum and maximum luminous output at 20mA. Tolerance within each bin is ±15%.

• V1: 710.0 – 900.0 mcd
• V2: 900.0 – 1120.0 mcd
• W1: 1120.0 – 1400.0 mcd
• W2: 1400.0 – 1800.0 mcd

3.3 Dominant Wavelength (Hue) Binning

Bins ensure color consistency by grouping LEDs based on their dominant wavelength. Tolerance within each bin is ±1 nm.

• J: 587.0 – 589.5 nm
• K: 589.5 – 592.0 nm
• L: 592.0 – 594.5 nm
• M: 594.5 – 597.0 nm

4. Performance Curve Analysis

Typical characteristic curves provide insight into the LED's behavior under varying conditions. These are essential for robust circuit design.

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

The I-V curve demonstrates the exponential relationship between current and voltage. The forward voltage (V_F) has a negative temperature coefficient, meaning it decreases slightly as the junction temperature increases. Designers must account for this when designing current-limiting circuits to prevent thermal runaway in parallel configurations.

4.2 Luminous Intensity vs. Forward Current

This curve shows that light output is approximately linear with current in the typical operating range (up to the maximum DC rating). Driving the LED beyond its absolute maximum ratings will lead to super-linear efficiency droop, increased heat, and accelerated lumen depreciation.

4.3 Luminous Intensity vs. Ambient Temperature

The light output of AlInGaP LEDs decreases as ambient temperature rises. This derating curve is critical for applications operating in elevated temperature environments, as it informs the necessary design margin to maintain required brightness levels.

4.4 Spectral Distribution

The spectral graph confirms the peak wavelength near 591nm and the narrow spectral half-width of approximately 15nm, which is characteristic of AlInGaP technology and results in a saturated yellow color.

5. Mechanical and Package Information

5.1 Package Dimensions

The LED conforms to an industry-standard SMD footprint. Key dimensions include a body size and lead spacing designed for reliable soldering and automated handling. All dimensions are in millimeters with a standard tolerance of ±0.1mm unless otherwise specified. The package features a dome-shaped clear lens.

5.2 Recommended PCB Attachment Pad Layout

A land pattern diagram is provided to ensure proper solder joint formation, thermal management, and mechanical stability. Adhering to this recommended footprint minimizes tombstoning and other soldering defects during reflow.

5.3 Polarity Identification

The cathode is typically marked on the device body. The datasheet should be consulted for the specific marking scheme. Correct polarity must be observed during assembly to prevent reverse bias damage.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Parameters

For lead-free (Pb-free) solder processes, the following profile is recommended:

• Pre-heat Temperature: 150°C to 200°C.
• Pre-heat Time: Maximum 120 seconds.
• Peak Body Temperature: Maximum 260°C.
• Time Above 260°C: Maximum 10 seconds.
• Maximum Number of Reflow Passes: Two.

The profile should comply with JEDEC standards. Board-specific characterization is necessary as thermal mass and layout vary.

6.2 Hand Soldering

If hand soldering is necessary, use a temperature-controlled iron.

• Iron Tip Temperature: Maximum 300°C.
• Soldering Time per Lead: Maximum 3 seconds.
• Important: Hand soldering should be limited to one-time repair only, not for initial assembly.

6.3 Cleaning

If cleaning is required post-solder, only use specified alcohol-based solvents such as isopropyl alcohol (IPA) or ethyl alcohol. Immersion should be at normal temperature for less than one minute. Unspecified chemical cleaners may damage the epoxy lens or package.

6.4 Storage and Handling

• ESD Precautions: This device is sensitive to electrostatic discharge (ESD). Proper ESD controls (wrist straps, grounded workstations, conductive flooring) must be used during handling.
• Moisture Sensitivity Level (MSL): The component is rated MSL 3. Once the original moisture-barrier bag is opened, the LEDs must be subjected to IR reflow within one week under ambient conditions not exceeding 30°C/60% RH.
• Long-Term Storage (Opened Bag): For storage beyond one week, bake the LEDs at 60°C for at least 20 hours before soldering, or store them in a sealed container with desiccant or in a nitrogen desiccator.
• Shelf Life (Sealed Bag): One year when stored at ≤ 30°C and ≤ 90% RH in the original moisture-proof packaging with desiccant.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied in embossed carrier tape for automated assembly.

• Tape Width: 8 mm.
• Reel Diameter: 7 inches (178 mm).
• Quantity per Reel: 3000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Packing Standard: Conforms to ANSI/EIA-481 specifications. Empty pockets are sealed with cover tape.

8. Application Suggestions and Design Considerations

8.1 Current Limiting

An LED is a current-driven device. Always use a series current-limiting resistor or a constant-current driver circuit. The resistor value can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Use the maximum V_F from the bin or datasheet to ensure sufficient current under all conditions.

8.2 Thermal Management

While the power dissipation is low, proper PCB layout is essential for longevity. Ensure adequate copper area around the solder pads to act as a heat sink, especially when operating near the maximum current or in high ambient temperatures. Avoid placing LEDs near other heat-generating components.

8.3 Optical Design

The 75-degree viewing angle provides a wide beam. For applications requiring a more focused beam, secondary optics (lenses, light guides) will be necessary. The dome lens offers good on-axis intensity suitable for direct viewing as an indicator.

8.4 Reliability and Lifetime

LED lifetime is typically defined as the point where luminous output degrades to 50% (L70) or 70% (L50) of its initial value. Operating the LED below its absolute maximum ratings, particularly in terms of current and temperature, is the primary factor in maximizing operational lifetime.

9. Frequently Asked Questions (Based on Technical Parameters)

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

Peak Wavelength (λ_P): The specific wavelength at which the LED emits the most optical power. It is a physical measurement from the spectrum. Dominant Wavelength (λ_d): The single wavelength of monochromatic light that would appear to have the same color as the LED to a standard human observer. It is calculated from the CIE chromaticity coordinates and is more relevant for color specification.

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

No. The forward voltage is only 1.7-2.5V. Connecting it directly to 3.3V would cause excessive current to flow, far exceeding the 25mA maximum, leading to immediate or rapid failure. A current-limiting resistor or regulator is always required.

9.3 Why is there a binning system for voltage and intensity?

Manufacturing variations in semiconductor processes cause slight differences in performance. Binning sorts LEDs into groups with tightly controlled parameters. This allows designers to select a bin that guarantees their design will function correctly (e.g., ensuring uniform brightness across multiple LEDs in an array by selecting the same intensity bin).

9.4 How do I interpret the MSL 3 rating?

MSL (Moisture Sensitivity Level) 3 means the package can be exposed to factory floor conditions ( ≤ 30°C / 60% RH) for up to 168 hours (7 days) after the bag is opened before reflow soldering is required. If this time is exceeded, the parts must be baked to remove absorbed moisture that could cause \"popcorning\" (package cracking) during reflow.

10. Technology Introduction and Trends

10.1 AlInGaP Technology Principle

Aluminum Indium Gallium Phosphide (AlInGaP) is a III-V semiconductor compound used primarily for producing high-efficiency LEDs in the red, orange, amber, and yellow regions of the visible spectrum. By adjusting the ratios of aluminum, indium, and gallium, the bandgap of the material can be tuned, which directly determines the wavelength (color) of the emitted light. AlInGaP LEDs are known for their high luminous efficacy and good temperature stability compared to older technologies like GaAsP.

10.2 Industry Trends

The general trend in SMD LEDs is toward higher efficiency (more lumens per watt), increased power density in smaller packages, and improved color consistency and rendering. There is also a strong drive for broader adoption of lead-free and halogen-free materials to meet stringent environmental regulations globally. The packaging technology continues to evolve to better manage heat extraction, which is the primary limiter of performance and lifetime in high-power applications.