Reverse Mount SMD LED Datasheet - Orange Color - 5mA Forward Current - 2.3V Forward Voltage - English Technical Document

1. Product Overview

This document details the specifications for a high-brightness, reverse mount Surface-Mount Device (SMD) Light Emitting Diode (LED). The device utilizes an Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor chip, which is known for its high luminous efficiency and excellent color purity, particularly in the orange to red spectrum. The primary application is as a compact, reliable indicator light in various electronic assemblies where space is constrained and a reverse mounting configuration is advantageous for design or aesthetic reasons.

The core advantages of this component include its compliance with RoHS (Restriction of Hazardous Substances) directives, making it an environmentally conscious choice. It is packaged on industry-standard 8mm tape wound onto 7-inch reels, ensuring compatibility with high-speed automated pick-and-place assembly equipment. Furthermore, the device is designed to withstand standard infrared (IR) reflow soldering processes commonly used in modern electronics manufacturing, facilitating easy integration into printed circuit board (PCB) assemblies.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The absolute maximum ratings define the stress limits beyond which permanent damage to the device may occur. These values should not be exceeded under any operating conditions.

• Power Dissipation (Pd): 75 mW. This is the maximum amount of power the LED package can dissipate as heat without degrading performance or reliability.
• Peak Forward Current (I_F(peak)): 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 overheating of the semiconductor junction.
• Continuous Forward Current (I_F): 30 mA DC. This is the maximum steady-state current that can be applied continuously.
• Reverse Voltage (V_R): 5 V. Applying a reverse voltage exceeding this value can cause breakdown and failure of the LED.
• Operating & Storage Temperature: -30°C to +85°C (operating), -40°C to +85°C (storage). These ranges ensure the LED's mechanical and electrical integrity.
• Soldering Temperature: Withstands 260°C for 10 seconds, compliant with lead-free (Pb-free) soldering profiles.

2.2 Electrical & Optical Characteristics

These parameters are measured at a standard test condition of an ambient temperature (T_a) of 25°C and a forward current (I_F) of 5 mA, unless otherwise noted.

• Luminous Intensity (I_V): Ranges from a minimum of 11.2 millicandelas (mcd) to a maximum of 71.0 mcd. The actual value for a specific unit depends on its assigned bin code (see Section 3).
• Viewing Angle (2θ_1/2): 130 degrees. This is the full angle at which the luminous intensity is half of the intensity measured on the central axis (0°). A wide viewing angle like this is typical for LEDs with a water-clear lens, providing a broad, diffuse light pattern suitable for indicator applications.
• Peak Wavelength (λ_P): Typically 611 nanometers (nm). This is the wavelength at which the spectral power output is greatest.
• Dominant Wavelength (λ_d): Typically 605 nm. This is the single wavelength perceived by the human eye that defines the color of the light, derived from the CIE chromaticity diagram. It is the key parameter for color specification.
• Spectral Bandwidth (Δλ): Typically 17 nm. This is the full width at half maximum (FWHM) of the emission spectrum, indicating the color purity. A smaller bandwidth indicates a more monochromatic light source.
• Forward Voltage (V_F): Ranges from 1.9V (min) to 2.3V (max) at 5 mA. This is the voltage drop across the LED when it is conducting current. Designers must ensure the driving circuit can provide sufficient voltage.
• Reverse Current (I_R): Maximum 10 µA at a reverse voltage of 5V. This is the small leakage current that flows when the LED is reverse-biased within its safe limit.
• Capacitance (C): Typically 40 pF measured at 0V bias and 1 MHz. This parasitic capacitance can be a consideration in high-frequency switching applications.

3. Binning System Explanation

To manage natural variations in the semiconductor manufacturing process, LEDs are sorted into performance bins. This ensures consistency within a production lot. For this product, binning is primarily based on luminous intensity.

The bin code list defines four distinct groups:

• Bin L: Luminous intensity from 11.2 mcd to 18.0 mcd.
• Bin M: Luminous intensity from 18.0 mcd to 28.0 mcd.
• Bin N: Luminous intensity from 28.0 mcd to 45.0 mcd.
• Bin P: Luminous intensity from 45.0 mcd to 71.0 mcd.

A tolerance of +/-15% is applied to the intensity values within each bin. Designers should select the appropriate bin based on the required brightness for their application, understanding that units from a higher bin (e.g., P) will be brighter than those from a lower bin (e.g., L) when driven under the same conditions.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Figure 1 for spectral distribution, Figure 5 for viewing angle), the textual data allows for analysis of key relationships.

Forward Current vs. Luminous Intensity: The luminous intensity is specified at I_F = 5mA. Generally, for AlInGaP LEDs, luminous intensity increases super-linearly with current at lower levels and then tends to saturate at higher currents due to thermal and efficiency droop. Operating significantly above the test current may yield higher output but must be carefully managed within the absolute maximum ratings for current and power dissipation.

Forward Current vs. Forward Voltage: The V_F range is given at 5mA. The forward voltage has a negative temperature coefficient, meaning it decreases as the junction temperature increases. It also increases logarithmically with current.

Temperature Dependence: The luminous output of LEDs decreases as the junction temperature rises. This characteristic is crucial for applications where the LED may operate in elevated ambient temperatures or where self-heating from high drive currents is significant. The specified operating temperature range of -30°C to +85°C defines the environment where the LED will function within its published specifications.

5. Mechanical & Package Information

The device conforms to an EIA (Electronic Industries Alliance) standard package outline. As a reverse mount type, the LED is intended to be mounted on the opposite side of the PCB from which the light is viewed, with the light emitting through a hole or aperture in the board. This creates a sleek, flush appearance on the user-facing side.

Detailed package dimensions, including body length, width, height, and lead positions, are provided in the datasheet drawings. These critical measurements are necessary for designing the PCB footprint, including the cutout for the lens and the solder pad layout.

Polarity Identification: The cathode is typically marked, often by a notch, a green dot, or a different lead length/shape. Correct polarity must be observed during assembly, as applying reverse voltage beyond 5V can damage the device.

Suggested Solder Pad Dimensions: The datasheet includes a recommended land pattern (solder pad geometry) for PCB design. Adhering to these recommendations promotes reliable solder joint formation during reflow, proper alignment, and good mechanical strength.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profile

A suggested infrared (IR) reflow profile is provided for lead-free (Pb-free) solder processes. Key parameters of this profile include:

• Pre-heat Zone: Ramp-up to 150-200°C.
• Soak/Pre-heat Time: Maximum 120 seconds to allow for temperature stabilization across the PCB.
• Peak Temperature: Maximum 260°C. The LED is rated to withstand this temperature for a maximum of 10 seconds.
• Time Above Liquidus (TAL): The time the solder is molten must be controlled to ensure proper joint formation without subjecting the LED to excessive thermal stress.

The profile is based on JEDEC standards, ensuring compatibility with standard surface-mount technology (SMT) assembly lines. It is critical to characterize the specific profile for a given PCB design, considering board thickness, component density, and solder paste type.

6.2 Hand Soldering

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

• Soldering iron temperature must not exceed 300°C.
• The soldering time must be limited to a maximum of 3 seconds per lead.
• This should be performed only once to avoid thermal damage to the plastic package and the internal wire bonds.

6.3 Cleaning

Only specified cleaning agents should be used. Recommended solvents include ethyl alcohol or isopropyl alcohol (IPA). The LED should be immersed at normal room temperature for less than one minute. Harsh or unspecified chemicals can damage the epoxy lens and package material, leading to discoloration, cracking, or delamination.

6.4 Storage & Handling

• ESD (Electrostatic Discharge) Precautions: LEDs are sensitive to static electricity. Proper ESD controls are mandatory, including the use of grounded wrist straps, anti-static mats, and conductive containers.
• Moisture Sensitivity: The package has a Moisture Sensitivity Level (MSL). For devices removed from their original moisture-proof packaging (with desiccant), it is recommended to complete IR reflow soldering within 672 hours (28 days) under storage conditions not exceeding 30°C and 60% relative humidity. If this window is exceeded, a bake-out 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

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

• Tape Width: 8 mm.
• Reel Diameter: 7 inches.
• Quantity per Reel: 3000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Packing Standards: Complies with ANSI/EIA-481 specifications. The tape pockets are sealed with a top cover tape. The maximum allowable number of consecutive empty pockets (missing components) is two.

The part number LTST-C230KFKT-5A uniquely identifies this specific variant: reverse mount, water-clear lens, AlInGaP chip, orange color.

8. Application Notes & Design Considerations

Typical Applications: This LED is suitable for general indicator purposes in consumer electronics, office equipment, communication devices, and household appliances. Its reverse mount design is ideal for front panels, control interfaces, and status displays where a clean, aperture-based look is desired.

Current Limiting: An external current-limiting resistor is almost always required when driving an LED from a voltage source. The resistor value (R) can be calculated using Ohm's Law: R = (V_source - V_F) / I_F. Use the maximum V_F from the datasheet (2.3V) to ensure sufficient current drive under all conditions. For example, to drive the LED at 5mA from a 5V supply: R = (5V - 2.3V) / 0.005A = 540 Ohms. A standard 560 Ohm resistor would be a safe choice.

Thermal Management: While power dissipation is low, continuous operation at high currents (e.g., near the 30mA maximum) in a high ambient temperature can raise the junction temperature. This reduces light output and can affect long-term reliability. Ensure adequate PCB copper area or thermal vias around the solder pads to help dissipate heat, especially for designs using multiple LEDs or driving LEDs hard.

Optical Design: The 130-degree viewing angle provides wide dispersion. For applications requiring a more focused beam, secondary optics (such as a lens mounted over the PCB aperture) would be necessary. The water-clear lens does not diffuse the light internally, so the light pattern will be defined by the chip geometry and the primary lens of the package.

9. Technical Comparison & Differentiation

The key differentiating feature of this component is its reverse mount configuration. Compared to standard top-emitting SMD LEDs, this design allows the PCB itself to act as a light guide and bezel, offering a unique aesthetic and potentially saving vertical space behind the panel.

The use of AlInGaP semiconductor technology is another significant advantage for orange/red colors. AlInGaP LEDs generally offer higher luminous efficacy and better temperature stability compared to older technologies like Gallium Arsenide Phosphide (GaAsP). This results in brighter, more consistent color output over the device's lifetime and operating temperature range.

Its compatibility with standard IR reflow and automatic placement makes it as easy to assemble as any other SMD component, minimizing production complexity despite its specialized mounting style.

10. Frequently Asked Questions (FAQ)

Q: What does "reverse mount" mean?
A: A reverse mount LED is designed to be installed on the side of the PCB opposite the viewing side. The light emits through a hole in the PCB, allowing the LED body to be hidden behind the panel for a seamless appearance.

Q: Can I drive this LED without a current-limiting resistor?
A: No. Connecting an LED directly to a voltage source exceeding its forward voltage will cause excessive current to flow, rapidly destroying the device. Always use a series resistor or a constant-current driver.

Q: The luminous intensity has a wide range (11.2 to 71.0 mcd). How do I know what I will get?
A: The specific intensity is determined by the bin code (L, M, N, P). You must specify the required bin when ordering. If a specific bin is not ordered, you may receive units from any bin within the product range.

Q: Is this LED suitable for outdoor use?
A: The operating temperature range is -30°C to +85°C, which covers many environments. However, the datasheet does not specify an Ingress Protection (IP) rating against dust and water. For outdoor use, additional sealing (conformal coating, gaskets) would be necessary to protect the LED and its solder joints from moisture and contaminants.

Q: How do I identify the anode and cathode?
A: Refer to the package marking diagram in the datasheet. Typically, the cathode is marked. When in doubt, use a multimeter in diode test mode; the LED will light dimly when forward-biased (positive lead on anode, negative on cathode).

11. Practical Design Example

Scenario: Designing a status indicator for a network router. The indicator should be a small orange dot on the front panel, flush with the surface.

1. PCB Layout: On the component (bottom) side of the PCB, design the footprint using the suggested solder pad dimensions from the datasheet. On the top (user-facing) side, create a small aperture (hole) in the solder mask and any overlays, aligned with the LED's lens position. The hole diameter should be slightly larger than the lens to avoid blocking light.
2. Circuit Design: The router's microcontroller operates at 3.3V. To drive the LED at a conservative 5mA, calculate the series resistor: R = (3.3V - 2.3V) / 0.005A = 200 Ohms. Use a standard 200 Ohm or 220 Ohm resistor placed in series on the same PCB layer as the LED.
3. Assembly: The PCB is assembled using a standard lead-free reflow process. The LED is placed automatically from the tape-and-reel onto the bottom-side pads. During reflow, it solders in place.
4. Final Assembly: The PCB is installed into the router chassis. The front panel has a small window aligned with the PCB aperture. When powered, the orange light shines through the aperture and the front panel window, creating a clean, modern indicator.

12. Technology Principle

Light Emitting Diodes are semiconductor devices that emit light through a process called electroluminescence. When a forward voltage is applied across the p-n junction, electrons from the n-type region and holes from the p-type region are injected into the active region. When these charge carriers recombine, energy is released in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material used in the active region.

This particular LED uses an Aluminum Indium Gallium Phosphide (AlInGaP) compound semiconductor. By precisely controlling the ratios of aluminum, indium, gallium, and phosphorus during crystal growth, engineers can tune the bandgap to produce light in the yellow, orange, and red spectrum with high efficiency. The AlInGaP material system is known for its high internal quantum efficiency and good performance at elevated temperatures compared to alternative materials for these colors.

13. Industry Trends

The LED industry continues to evolve towards higher efficiency, smaller form factors, and greater integration. For indicator-type LEDs like this one, trends include:

• Miniaturization: Development of even smaller package sizes (e.g., 0402, 0201 metric) to save PCB real estate in increasingly compact devices.
• Higher Brightness at Lower Currents: Improvements in chip design and materials allow for sufficient brightness at very low drive currents (e.g., 1-2 mA), reducing overall system power consumption, which is critical for battery-powered IoT devices.
• Improved Color Consistency: Tighter binning specifications and advanced manufacturing controls lead to less variation in color and brightness within a production batch, important for applications using multiple LEDs (e.g., light bars, arrays).
• Enhanced Reliability: Ongoing improvements in package materials (epoxy, silicone) to better withstand higher reflow temperatures, harsher environmental conditions, and provide longer operational lifetimes.
• Integrated Solutions: Growth of LEDs with built-in resistors or driver ICs, simplifying circuit design by reducing external component count.

The reverse mount configuration itself is part of a broader trend towards more aesthetically integrated and mechanically robust lighting solutions in consumer and industrial electronics.