SMD LED LTST-C190KFKT-5A Datasheet - Orange AlInGaP - 5mA - 20mA - 50mW - English Technical Document

1. Product Overview

This document details the specifications for a compact, high-brightness Surface-Mount Device (SMD) LED. Designed for automated assembly processes, this component is ideal for space-constrained applications across a broad spectrum of consumer and industrial electronics.

1.1 Features

• Compliant with RoHS environmental standards.
• Utilizes an ultra-bright Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor chip for efficient orange light emission.
• Packaged on 8mm tape wound onto 7-inch diameter reels, suitable for automated pick-and-place equipment.
• Standardized EIA package footprint ensures broad compatibility.
• Logic-level compatible drive requirements.
• Designed to withstand standard infrared (IR) reflow soldering profiles used in PCB assembly.

1.2 Target Applications

This LED is suited for various indicator and backlighting functions, including but not limited to: status indicators in telecommunications and network equipment, keyboard/keypad backlighting, symbolic illumination on control panels, and integration into micro-displays and home appliances.

2. Technical Specifications Deep Dive

The following sections provide a detailed analysis of the device's electrical, optical, and environmental limits and characteristics.

2.1 Absolute Maximum Ratings

These values represent stress limits that must not be exceeded under any conditions, as permanent damage may occur. Operation should be maintained within the recommended operating conditions detailed later.

• Power Dissipation (Pd): 50 mW
• Peak Forward Current (I_F(PEAK)): 40 mA (pulsed at 1/10 duty cycle, 0.1ms pulse width)
• Continuous Forward Current (I_F): 20 mA DC
• Reverse Voltage (V_R): 5 V
• Operating Temperature Range (T_opr): -30°C to +85°C
• Storage Temperature Range (T_stg): -40°C to +85°C
• Soldering Temperature: Withstands 260°C for 10 seconds (Pb-free process).

2.2 Electrical & Optical Characteristics

Measured at an ambient temperature (T_a) of 25°C. Typical values are provided for design guidance, while minimum and maximum values define the guaranteed performance window.

• Luminous Intensity (I_V): 18.0 - 71.0 mcd (measured at I_F = 5mA). The intensity is categorized into specific bins (see Section 3).
• Viewing Angle (2θ_1/2): 130 degrees. This wide viewing angle is defined as the full angle where luminous intensity drops to half of its peak axial value, making it suitable for applications requiring broad visibility.
• Peak Wavelength (λ_P): 611 nm (typical). This is the wavelength at which the spectral power output is maximum.
• Dominant Wavelength (λ_d): 605 nm (typical at I_F=5mA). This is the single wavelength perceived by the human eye that defines the color, in this case, orange.
• Spectral Bandwidth (Δλ): 17 nm (typical). This defines the purity of the color; a narrower bandwidth indicates a more saturated color.
• Forward Voltage (V_F): 2.0V (min), 2.4V (typ) at I_F = 5mA.
• Reverse Current (I_R): 10 μA (max) at V_R = 5V.

3. Binning System Explanation

To ensure consistency in production, LEDs are sorted into performance bins. This allows designers to select components that meet specific brightness requirements for their application.

3.1 Luminous Intensity Binning

The luminous intensity is categorized into three primary bins (M, N, P) based on measurement at 5mA. Each bin has a tolerance of ±15%.

• Bin Code M: 18.0 mcd (Min) to 28.0 mcd (Max)
• Bin Code N: 28.0 mcd (Min) to 45.0 mcd (Max)
• Bin Code P: 45.0 mcd (Min) to 71.0 mcd (Max)

Selecting a higher bin code (e.g., P) guarantees a brighter LED, which may be necessary for high-ambient-light conditions or longer viewing distances.

4. Performance Curve Analysis

While specific graphical curves are referenced in the source document, their implications are critical for design.

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

The LED exhibits a non-linear I-V characteristic typical of diodes. The forward voltage (V_F) has a positive temperature coefficient, meaning it decreases slightly as the junction temperature increases. Designers must use a current-limiting resistor or constant-current driver to ensure stable light output and prevent thermal runaway, as the LED is a current-operated device.

4.2 Luminous Intensity vs. Forward Current

The light output is approximately proportional to the forward current within the specified operating range. However, efficiency may drop at very high currents due to increased thermal effects. Operating at or below the typical test current of 5mA is common for indicator applications to balance brightness and longevity.

4.3 Temperature Dependence

The luminous intensity of AlInGaP LEDs generally decreases with increasing junction temperature. For applications operating at the upper end of the temperature range (+85°C), derating the drive current may be necessary to maintain target brightness and device reliability over its lifetime.

5. Mechanical & Packaging Information

5.1 Package Dimensions

The device conforms to a standard SMD footprint. Critical dimensions include body length, width, and height, as well as the placement and size of the solderable terminals. All dimensional tolerances are typically ±0.1mm unless otherwise specified. The lens is water-clear, allowing the native orange color of the AlInGaP chip to be visible.

5.2 Polarity Identification & Recommended PCB Pad Layout

The cathode is typically marked on the device body, often with a notch, green dot, or other visual indicator. A recommended land pattern (footprint) for the printed circuit board is provided to ensure proper solder joint formation, reliable electrical connection, and mechanical stability during reflow. Adhering to this pattern helps prevent tombstoning (component standing on end) or poor solder wetting.

6. Soldering & Assembly Guidelines

6.1 IR Reflow Soldering Profile

The component is compatible with lead-free (Pb-free) soldering processes. A suggested reflow profile is provided, which typically includes: a pre-heat/soak zone (e.g., 150-200°C for up to 120 seconds), a rapid temperature ramp, a peak temperature zone not exceeding 260°C for a maximum of 10 seconds, and a controlled cooling phase. The profile should be characterized for the specific PCB assembly to ensure all components are properly soldered without damage.

6.2 Hand Soldering

If manual soldering is necessary, use a temperature-controlled soldering iron set to a maximum of 300°C. The contact time with the solder pad should be limited to 3 seconds or less per joint to prevent excessive heat transfer to the LED die, which can degrade performance or cause failure.

6.3 Cleaning

Post-solder cleaning should be performed with approved solvents. Isopropyl alcohol (IPA) or ethyl alcohol are recommended. The LED should be immersed at room temperature for less than one minute. Harsh or unspecified chemicals must be avoided as they can damage the plastic package or lens.

6.4 Storage & Handling

Electrostatic Discharge (ESD): This device is sensitive to ESD. Proper handling procedures are mandatory, including the use of grounded wrist straps, anti-static mats, and ESD-safe packaging. All equipment must be properly grounded.

Moisture Sensitivity: The package has a Moisture Sensitivity Level (MSL) rating. If the original sealed moisture-barrier bag is opened, the components should be subjected to IR reflow soldering within one week (168 hours) under controlled humidity conditions (<60% RH at <30°C). For storage beyond this period, baking at approximately 60°C for at least 20 hours is required before soldering to remove absorbed moisture and prevent \"popcorning\" (package cracking) during reflow.

7. Packaging & Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied on embossed carrier tape with a protective cover tape. Key specifications include: tape width of 8mm, reel diameter of 7 inches (178mm), and a standard quantity of 4000 pieces per full reel. The packaging conforms to ANSI/EIA-481 standards. A minimum order quantity for remnants may apply.

8. Application Notes & Design Considerations

8.1 Drive Circuit Design

An LED is a current-driven device. To ensure uniform brightness and prevent current hogging (where one LED in a parallel string draws more current than others), it is strongly recommended to use a individual current-limiting resistor in series with each LED, even when driven from a constant-voltage source. The resistor value (R) can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F, where V_F is the forward voltage of the LED at the desired current I_F.

8.2 Thermal Management

While the power dissipation is low (50mW max), effective thermal management on the PCB is still important for long-term reliability, especially at high ambient temperatures or when driven at higher currents. Ensuring adequate copper area around the solder pads helps dissipate heat from the LED junction.

8.3 Application Limitations

This product is designed for general-purpose electronic equipment. It is not specifically rated or tested for safety-critical applications where failure could lead to direct risk to life or health, such as in aviation, medical life-support, or transportation control systems. For such applications, components with appropriate safety certifications must be selected.

9. Technical Comparison & Differentiation

The key differentiator of this LED is its use of an AlInGaP chip for orange emission. Compared to older technologies like GaAsP, AlInGaP offers significantly higher luminous efficiency and better temperature stability, resulting in brighter and more consistent light output over a wide operating range. The 130-degree wide viewing angle is another advantageous feature for applications requiring off-axis visibility.

10. Frequently Asked Questions (FAQ)

10.1 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 that the human eye perceives as the color of the light, calculated from the CIE chromaticity diagram. For monochromatic LEDs like this orange one, they are often close, but λ_d is the more relevant parameter for color specification.

10.2 Can I drive this LED without a current-limiting resistor if using a constant-current power supply?

Yes, a constant-current driver is an excellent method to drive LEDs as it directly regulates the primary variable (current) that determines light output. In this case, an external series resistor is not necessary for current regulation, but may sometimes be used for other purposes like pulse shaping or redundancy.

10.3 Why is there a binning system for luminous intensity?

Manufacturing variations cause slight differences in light output even within the same product batch. Binning sorts these components into groups with guaranteed minimum and maximum brightness levels. This allows designers to select a bin that meets their application's brightness requirements precisely, ensuring consistency in the final product's appearance.

11. Design-in Case Study Example

Scenario: Designing a status indicator panel for a network router that must be clearly visible in a well-lit office environment from various angles.
Selection Rationale: The wide 130-degree viewing angle of this LED ensures visibility even when not viewed directly head-on. The high-brightness AlInGaP technology (selecting Bin P, 45-71 mcd) provides sufficient luminous intensity to overcome ambient light. Its SMD format allows for compact, automated assembly on the router's main PCB.
Circuit Design: The panel has 5 indicator LEDs. They are driven from the router's 3.3V logic supply. Using the typical V_F of 2.4V at 5mA, a series resistor of approximately (3.3V - 2.4V) / 0.005A = 180 Ohms is used for each LED. This simple, reliable design ensures consistent brightness across all indicators.

12. Technology Principle Introduction

This LED is based on Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the active region where they recombine. This recombination process releases energy in the form of photons (light). The specific bandgap energy of the AlInGaP alloy determines the wavelength (color) of the emitted light, which in this case is in the orange spectrum (~605-611 nm). The water-clear epoxy package acts as a lens, shaping the light output to achieve the specified viewing angle.

13. Industry Trends

The general trend in SMD indicator LEDs continues toward higher efficiency (more light output per unit of electrical power), improved color saturation, and smaller package sizes to enable denser PCB designs. There is also a growing emphasis on enhanced reliability under harsh conditions (higher temperature, humidity) and stricter adherence to environmental regulations beyond RoHS, such as halogen-free materials. The drive for automation in manufacturing further solidifies the importance of components compatible with standard tape-and-reel packaging and reflow processes.