LTST-S320KFKT Orange SMD LED Datasheet - EIA Package - 20mA - AlInGaP Chip - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a high-brightness, side-looking Surface Mount Device (SMD) Light Emitting Diode (LED). The device utilizes an Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor chip, which is renowned for producing efficient and bright light in the orange-red spectrum. The package is designed with a water-clear lens to maximize light output and is constructed with tin-plated terminations for excellent solderability. It is fully compliant with RoHS (Restriction of Hazardous Substances) directives, classifying it as a green product suitable for modern electronic manufacturing.

The LED is supplied in industry-standard 8mm tape on 7-inch diameter reels, making it fully compatible with high-speed automated pick-and-place assembly equipment. Its design is also compatible with infrared (IR) reflow soldering processes, which is the standard for mass production of surface-mount circuit boards. The electrical characteristics are designed to be compatible with standard integrated circuit (IC) logic levels, simplifying drive circuit design.

2. Technical Parameters: In-Depth Objective Interpretation

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed and should be avoided in reliable design.

• Power Dissipation (Pd): 75 mW. This is the maximum amount of power the LED package can dissipate as heat without degrading performance or lifespan. Exceeding this limit risks thermal runaway and failure.
• Peak Forward Current (I_FP): 80 mA. This is the maximum allowable instantaneous forward current, typically specified under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to prevent excessive junction temperature rise.
• DC Forward Current (I_F): 30 mA. This is the maximum continuous forward current recommended for reliable long-term operation. The typical operating condition specified in the optical characteristics is 20mA.
• Reverse Voltage (V_R): 5 V. Applying a reverse bias voltage exceeding this value can cause breakdown and catastrophic failure of the LED junction.
• Operating & Storage Temperature: -30°C to +85°C (operating), -40°C to +85°C (storage). These define the environmental limits for device functionality and non-operational storage, respectively.
• Infrared Soldering Condition: 260°C for 10 seconds. This defines the peak temperature and time tolerance for the reflow soldering process, critical for Pb-free assembly.

2.2 Electro-Optical Characteristics

Measured at an ambient temperature (T_a) of 25°C, these parameters define the device's performance under standard test conditions.

• Luminous Intensity (I_V): 45.0 - 90.0 mcd (millicandela) at I_F = 20mA. This is the perceived brightness of the LED as measured by a sensor filtered to match the human eye's photopic response (CIE curve). The wide range indicates a binning system is used (see Section 3).
• Viewing Angle (2θ_1/2): 130 degrees. This is the full angle at which the luminous intensity drops to half of its value measured on-axis. A 130° angle indicates a very wide viewing pattern, typical for side-emitting LEDs with a clear lens.
• Peak Wavelength (λ_P): 611 nm. This is the wavelength at which the spectral power output of the LED is at its maximum. It is a physical property of the AlInGaP chip material.
• Dominant Wavelength (λ_d): 605 nm. Derived from the CIE chromaticity diagram, this is the single wavelength that best represents the perceived color of the LED to the human eye. It is the key parameter for color specification.
• Spectral Line Half-Width (Δλ): 17 nm. This indicates the spectral purity or bandwidth of the emitted light, measured as the width of the spectrum at half its maximum power. A value of 17nm is typical for AlInGaP LEDs.
• Forward Voltage (V_F): 2.0V (Min), 2.4V (Typ) at I_F = 20mA. This is the voltage drop across the LED when operating. It is crucial for designing the current-limiting circuitry.
• Reverse Current (I_R): 10 μA (Max) at V_R = 5V. This is the small leakage current that flows when the device is reverse-biased within its maximum rating.

3. Binning System Explanation

To ensure consistent color and brightness in production, LEDs are sorted into performance bins. For this product, binning is applied to Luminous Intensity.

The bin code list specifies the minimum and maximum luminous intensity for each bin code when driven at the standard 20mA test current:

• Bin P: 45.0 - 71.0 mcd
• Bin Q: 71.0 - 112.0 mcd
• Bin R: 112.0 - 180.0 mcd
• Bin S: 180.0 - 280.0 mcd

A tolerance of +/-15% is applied to each intensity bin. This means an LED labeled as Bin Q could measure between approximately 60.4 mcd and 128.8 mcd, ensuring tighter grouping than the raw bin limits might suggest. Designers should account for this intensity variation when designing for minimum brightness requirements.

4. Performance Curve Analysis

The datasheet references typical performance curves which are essential for understanding device behavior under non-standard conditions. While the specific graphs are not reproduced in the text, their implications are standard.

• Relative Luminous Intensity vs. Forward Current: This curve would show that light output is approximately proportional to forward current in the normal operating range but will eventually saturate or roll off at very high currents due to thermal and efficiency effects.
• Relative Luminous Intensity vs. Ambient Temperature: For AlInGaP LEDs, luminous intensity typically decreases as junction temperature increases. This curve is critical for applications operating in elevated temperature environments.
• Forward Voltage vs. Forward Current: This exponential curve shows the relationship that defines the LED's V_F. It is non-linear, emphasizing the need for current control, not voltage control.
• Spectral Distribution: A graph showing the relative power emitted across wavelengths, peaking at 611nm with a characteristic shape and 17nm half-width.

5. Mechanical and Package Information

The device conforms to an EIA (Electronic Industries Alliance) standard package outline for side-looking LEDs. Detailed dimensioned drawings are provided in the datasheet, including key measurements such as overall length, width, height, lead spacing, and lens position. A suggested soldering pad layout (land pattern) is also provided to ensure a reliable solder joint and proper alignment during reflow. The polarity of the device is clearly indicated, typically by a marking on the package or an asymmetrical feature in the footprint. The tape and reel packaging dimensions are specified, confirming compatibility with standard 8mm carrier tape and 7-inch reels.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

A suggested infrared reflow profile is provided for lead-free (Pb-free) solder processes. The critical parameters include a pre-heat stage, a defined ramp-up rate, a peak temperature not exceeding 260°C, and a time above liquidus (TAL) sufficient for proper solder joint formation. The profile is based on JEDEC standards to ensure package reliability. It is emphasized that the optimal profile depends on the specific PCB design, solder paste, and oven, so board-level characterization is recommended.

6.2 Manual Soldering

If hand soldering is necessary, it should be performed with a soldering iron tip temperature not exceeding 300°C, and the soldering time should be limited to a maximum of 3 seconds per lead. This should be done only once to prevent thermal damage to the plastic package and the semiconductor die.

6.3 Cleaning

If cleaning after soldering is required, only specified solvents should be used. The datasheet recommends immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute. Unspecified chemical cleaners may damage the epoxy lens or package material.

6.4 Storage and Handling

• ESD Precautions: LEDs are sensitive to electrostatic discharge (ESD). Handling should be performed using wrist straps, anti-static gloves, and properly grounded equipment.
• Moisture Sensitivity: While the sealed reel provides protection, once the original moisture-proof bag is opened, the LEDs should be used within one week or stored in a controlled environment (<30°C, <60% RH). For extended storage out of the bag, baking at 60°C for 20+ hours before soldering is recommended to remove absorbed moisture and prevent \"popcorning\" during reflow.

7. Packaging and Ordering Information

The standard packaging is 3000 pieces per 7-inch reel. The tape is sealed with a cover tape. There are specifications for the maximum number of consecutive empty pockets (two) and a minimum packing quantity for remainder reels (500 pieces). The packaging follows ANSI/EIA-481 specifications. The part number LTST-S320KFKT uniquely identifies this product: an orange, side-looking, AlInGaP LED in this specific package.

8. Application Suggestions

8.1 Typical Application Scenarios

This side-looking, high-brightness orange LED is well-suited for applications requiring wide-angle status indication, backlighting for small displays or panels, and decorative lighting where a specific orange hue is desired. Its SMD format and compatibility with reflow soldering make it ideal for modern, densely populated printed circuit boards (PCBs) in consumer electronics, industrial control panels, automotive interior lighting, and instrumentation.

8.2 Design Considerations

• Current Driving: Always drive an LED with a constant current source or a voltage source with a series current-limiting resistor. The recommended operating current is 20mA, but it can be driven up to the maximum DC rating of 30mA for higher brightness at the cost of reduced lifetime and increased heat.
• Thermal Management: While the power dissipation is low, ensuring adequate PCB copper area or thermal vias around the solder pads can help dissipate heat, especially when operating at higher currents or in warm environments. This maintains brightness and longevity.
• Optical Design: The 130-degree viewing angle provides a very wide emission pattern. For applications requiring a more directed beam, external lenses or light guides may be necessary.

9. Technical Comparison and Differentiation

The key differentiators of this LED are its combination of technologies: the use of an AlInGaP chip for high-efficiency orange light, a side-looking package geometry for wide-angle emission, and tin-plated leads for excellent solderability with both leaded and lead-free processes. Compared to older technology like GaAsP, AlInGaP offers significantly higher luminous efficiency and better temperature stability. The EIA-standard package ensures mechanical compatibility and easy sourcing of replacements or alternatives from other manufacturers.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: What resistor value should I use with a 5V supply?

A: Using the typical V_F of 2.4V at 20mA, the resistor would need to drop 5V - 2.4V = 2.6V. Using Ohm's Law (R = V/I), R = 2.6V / 0.02A = 130 Ohms. A standard 130Ω or 150Ω resistor would be appropriate. Always calculate based on the maximum possible V_F to ensure the current does not exceed the maximum rating.

Q: Can I pulse this LED for higher brightness?

A: Yes, the datasheet specifies a Peak Forward Current of 80mA at a 1/10 duty cycle with a 0.1ms pulse width. Pulsing at a higher current (e.g., 60-80mA) with a low duty cycle can achieve a higher perceived peak brightness without exceeding the average power dissipation limits. The driver circuit must ensure pulse parameters are within spec.

Q: Why is the Dominant Wavelength (605nm) different from the Peak Wavelength (611nm)?

A> The peak wavelength is a physical measurement of the spectrum's highest point. The dominant wavelength is a calculated value based on how the human eye perceives color from the entire spectrum emitted. The difference accounts for the shape and width of the emission spectrum.

11. Practical Design and Usage Case

Case: Designing a Status Indicator Panel for an Industrial Controller. A designer needs multiple orange status LEDs on a front panel PCB. They choose this LED for its wide viewing angle (130°), ensuring visibility from various angles in a control room. They design the PCB with the recommended solder pad layout to ensure self-alignment during reflow. They drive each LED at 20mA using a constant-current LED driver IC to ensure uniform brightness across all units, accounting for the +/-15% bin tolerance. They specify Bin Q or higher from the manufacturer to guarantee a minimum brightness level for clear indication. The board is assembled using the suggested Pb-free reflow profile, and the final product undergoes thermal cycling tests to verify reliability in the target operating environment of up to 70°C.

12. Principle of Operation Introduction

An LED is a semiconductor diode. When a forward voltage is applied across its terminals (anode positive relative to cathode), electrons from the n-type semiconductor material recombine with holes from the p-type material at the junction between them. This recombination process releases energy in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the energy bandgap of the semiconductor material. In this device, the AlInGaP (Aluminum Indium Gallium Phosphide) compound semiconductor has a bandgap that corresponds to orange light emission (~605-611 nm). The water-clear epoxy lens encapsulates the chip, provides mechanical protection, and shapes the light output pattern.

13. Technology Trends

The general trend in LED technology is toward higher efficiency (more lumens per watt), improved color rendering, higher power density, and smaller package sizes. For indicator-type SMD LEDs like this one, trends include the development of even wider viewing angles, lower operating voltages to match modern low-power logic, and enhanced reliability under harsh environmental conditions (higher temperature, humidity). There is also a continuous drive for manufacturing process optimization to reduce cost while maintaining performance. The use of AlInGaP for orange/red colors remains standard due to its high efficiency, though research into perovskite and other novel materials is ongoing for future applications.