Reverse Mount SMD LED LTST-C230TGKT Datasheet - Green 530nm - 3.2V - 76mW - 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 component utilizes an InGaN (Indium Gallium Nitride) semiconductor chip to produce green light. It is designed for automated assembly processes and is compatible with infrared (IR) reflow soldering, making it suitable for high-volume electronics manufacturing. The LED is packaged on 8mm tape wound onto 7-inch reels, adhering to EIA (Electronic Industries Alliance) standard packaging for consistent handling and placement.

1.1 Core Features and Advantages

• RoHS Compliant & Green Product: Manufactured without the use of hazardous substances like lead, mercury, and cadmium, meeting environmental regulations.
• Reverse Mount Design: The package is engineered for mounting where the light-emitting surface faces the printed circuit board (PCB), allowing for specific optical designs or space-saving layouts.
• Ultra-Bright InGaN Chip: The InGaN material system enables high luminous efficiency and a well-defined green color output.
• Automation Compatibility: The tape-and-reel packaging and standardized footprint ensure compatibility with high-speed automatic pick-and-place equipment.
• Reflow Solderable: Withstands standard infrared reflow soldering profiles used in surface-mount technology (SMT) assembly lines.

2. Technical Specifications Deep Dive

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed.

• Power Dissipation (Pd): 76 mW
• Peak Forward Current (I_F(peak)): 100 mA (at 1/10 duty cycle, 0.1ms pulse width)
• DC Forward Current (I_F): 20 mA
• Operating Temperature Range (T_opr): -20°C to +80°C
• Storage Temperature Range (T_stg): -30°C to +100°C
• Infrared Soldering Condition: 260°C peak temperature for a maximum of 10 seconds.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at an ambient temperature (T_a) of 25°C under specified test conditions.

• Luminous Intensity (I_V): Ranges from a minimum of 71.0 mcd to a maximum of 450.0 mcd at a forward current (I_F) of 20 mA. Measured using a sensor filtered to match the human eye's photopic response (CIE curve).
• Viewing Angle (2θ_1/2): 130 degrees. This is the full angle at which the light intensity drops to half of its peak (on-axis) value.
• Peak Emission Wavelength (λ_P): 530 nm. The wavelength at which the spectral power output is highest.
• Dominant Wavelength (λ_d): 525 nm (typical). This is the single wavelength perceived by the human eye that defines the color of the LED, derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): 35 nm (typical). This indicates the spectral purity; a smaller value means a more monochromatic light source.
• Forward Voltage (V_F): Typically 3.20V, with a range from 2.80V to 3.60V at I_F = 20 mA.
• Reverse Current (I_R): Maximum 10 μA when a reverse voltage (V_R) of 5V is applied. Important: This LED is not designed for operation under reverse bias; this test parameter is for leakage characterization only.

2.3 Electrostatic Discharge (ESD) Caution

The LED is sensitive to electrostatic discharge and voltage surges. Proper ESD control measures are mandatory during handling, including the use of grounded wrist straps, anti-static gloves, and ensuring all equipment is properly grounded to prevent latent or catastrophic failure.

3. Binning System Explanation

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

3.1 Forward Voltage Binning (Unit: V @ 20mA)

Tolerance on each bin is ±0.1V.

• D7: 2.80 – 3.00V
• D8: 3.00 – 3.20V
• D9: 3.20 – 3.40V
• D10: 3.40 – 3.60V

3.2 Luminous Intensity Binning (Unit: mcd @ 20mA)

Tolerance on each bin is ±15%.

• Q: 71.0 – 112.0 mcd
• R: 112.0 – 180.0 mcd
• S: 180.0 – 280.0 mcd
• T: 280.0 – 450.0 mcd

3.3 Dominant Wavelength Binning (Unit: nm @ 20mA)

Tolerance for each bin is ±1nm.

• AP: 520.0 – 525.0 nm
• AQ: 525.0 – 530.0 nm
• AR: 530.0 – 535.0 nm

4. Performance Curve Analysis

The datasheet references typical performance curves (e.g., relative luminous intensity vs. forward current, forward voltage vs. temperature, spectral distribution). These curves are essential for understanding device behavior under non-standard conditions.

• I-V/L-I Curves: Show the relationship between forward current (I_F), forward voltage (V_F), and light output (Luminous Intensity). Light output is generally proportional to current, but efficiency may drop at very high currents due to heating.
• Temperature Dependence: The forward voltage typically decreases with increasing junction temperature, while luminous intensity also decreases. Designers must account for thermal management to maintain consistent brightness.
• Spectral Distribution: A graph showing light output power across wavelengths, centered around the peak wavelength of 530 nm with a typical half-width of 35 nm.

5. Mechanical & Package Information

5.1 Package Dimensions

The LED comes in a standard SMD package. All dimensions are in millimeters with a general tolerance of ±0.10 mm unless otherwise specified. The drawing includes key measurements such as overall length, width, height, and the size/position of the cathode/anode pads.

5.2 Suggested Soldering Pad Layout

A recommended PCB land pattern (footprint) is provided to ensure reliable solder joint formation during reflow. Adhering to this pattern helps prevent tombstoning (component standing on end) and ensures proper alignment.

5.3 Polarity Identification

The component features a marking or physical feature (e.g., a notch, a beveled corner, or a dot) to identify the cathode. Correct polarity must be observed during PCB layout and assembly.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profile

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

• Pre-heat: 150–200°C for a maximum of 120 seconds to gradually heat the board and activate flux.
• Peak Temperature: Maximum of 260°C.
• Time Above Liquidus: The component should be exposed to the peak temperature for a maximum of 10 seconds. Reflow should not be performed more than twice.

The profile is based on JEDEC standards to ensure reliable mounting without damaging the LED package.

6.2 Hand Soldering (If Necessary)

If manual soldering is required, use a temperature-controlled iron:

• Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per pad. Limit to one soldering cycle only.

6.3 Cleaning

If post-solder cleaning is necessary, only use specified solvents to avoid damaging the plastic lens and package. Recommended agents are ethyl alcohol or isopropyl alcohol at normal room temperature. Immersion time should be less than one minute. Do not use ultrasonic cleaning unless explicitly verified as safe for this component.

7. Packaging & Ordering Information

7.1 Tape and Reel Specifications

• Carrier Tape Width: 8 mm.
• Reel Diameter: 7 inches.
• Quantity per Reel: 3000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Pocket Sealing: Empty pockets are sealed with cover tape.
• Missing Components: A maximum of two consecutive missing LEDs is allowed per the specification (ANSI/EIA 481).

8. Storage and Handling

• Sealed Package: Store at ≤30°C and ≤90% Relative Humidity (RH). The shelf life is one year when stored in the original moisture-barrier bag with desiccant.
• Opened Package: For components removed from the sealed bag, the storage environment must not exceed 30°C and 60% RH. It is recommended to complete IR reflow soldering within 672 hours (28 days, MSL 2a) of exposure. For longer storage outside the original bag, use a sealed container with desiccant or a nitrogen desiccator. Components exposed for more than 672 hours should be baked at approximately 60°C for at least 20 hours before assembly to remove absorbed moisture and prevent "popcorning" during reflow.

9. Application Notes & Design Considerations

9.1 Typical Application Scenarios

This high-brightness green LED is suitable for a wide range of applications requiring status indication, backlighting, or decorative lighting, including:

• Consumer electronics (e.g., indicators on appliances, audio equipment).
• Industrial control panels and human-machine interfaces (HMIs).
• Automotive interior lighting (non-critical applications, subject to further qualification).
• Signage and decorative light strips.

Critical Note: This product is intended for ordinary electronic equipment. For applications where failure could jeopardize life or health (aviation, medical devices, safety systems), consultation with the manufacturer for suitability and additional reliability requirements is essential prior to design-in.

9.2 Circuit Design

• Current Limiting: An LED is a current-driven device. Always use a series current-limiting resistor or a constant-current driver circuit to prevent exceeding the maximum DC forward current (20 mA). The resistor value can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F.
• Voltage Selection: Account for the forward voltage bin (D7-D10) in your design to ensure proper current regulation across all units, especially when connecting multiple LEDs in series.
• Reverse Voltage Protection: As the device is not designed for reverse operation, ensure circuit designs prevent the application of any reverse bias across the LED. In circuits where reverse voltage is possible (e.g., AC coupling or inductive loads), consider adding a protection diode in parallel (reverse-biased relative to the LED).

9.3 Thermal Management

While the power dissipation is relatively low (76 mW), effective thermal management on the PCB is crucial for maintaining long-term reliability and consistent light output. Ensure adequate copper area around the solder pads to act as a heat sink, especially when operating at high ambient temperatures or near the maximum current.

10. Technical Comparison & Differentiation

This reverse-mount LED offers specific advantages:

• vs. Standard Top-Emitting LEDs: The reverse-mount design allows for innovative optical solutions where light is directed through the PCB or reflected from it, enabling thinner product designs or specific light guides.
• vs. Non-Automation Friendly Packages: The tape-and-reel packaging and robust SMD construction provide significant cost and reliability benefits in high-volume automated assembly compared to through-hole LEDs or loose-packaged components.
• vs. Wider Viewing Angle LEDs: The 130-degree viewing angle provides a good balance between wide visibility and forward intensity. For applications requiring a very narrow beam, a lensed version or a different package would be more suitable.

11. Frequently Asked Questions (FAQs)

11.1 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. It is calculated from the CIE color coordinates. For a monochromatic green LED, these values are often close, as is the case here (530 nm vs. 525 nm).

11.2 Can I drive this LED with a 5V supply directly?

No. Connecting a 5V supply directly across the LED would attempt to force a very high current through it, almost certainly exceeding the absolute maximum rating and causing immediate failure. You must always use a current-limiting mechanism, such as a resistor. For example, with a 5V supply and a typical V_F of 3.2V at 20 mA, a series resistor of (5V - 3.2V) / 0.02A = 90 Ohms (a standard 91 Ohm resistor) would be required.

11.3 Why is the storage condition after opening the bag so strict?

SMD packages can absorb moisture from the atmosphere. During the high-temperature reflow soldering process, this trapped moisture can rapidly vaporize, creating internal pressure that can delaminate the package or crack the die (a phenomenon known as "popcorning" or "moisture-induced stress"). The specified storage conditions and bake requirements are designed to mitigate this risk.

12. Design-in Case Study Example

Scenario: Designing a status indicator for a portable medical device that requires a clear, bright green signal. The PCB is densely packed, and the indicator needs to be mounted on the bottom side, with light piped through a small hole in the enclosure.
Solution: The reverse-mount LED is an ideal choice. It can be placed on the bottom of the PCB with its emitting surface facing the board. A small via or opening in the PCB copper layer directly under the LED allows light to pass through to the housing's light pipe. The 130-degree viewing angle ensures good coupling into the light guide. The designer selects bins AQ (525-530 nm) for consistent green color and S or T for high brightness. A constant-current driver set to 15-18 mA is used to ensure long life and stable output, accounting for the forward voltage bin spread. Strict ESD and moisture control procedures are followed during assembly.

13. Technology Principle Introduction

This LED is based on InGaN semiconductor technology. In an LED, electrical current flows across a p-n junction formed by different semiconductor materials (InGaN for the active region). When electrons recombine with holes in this active region, energy is released in the form of photons (light). The specific composition of the Indium, Gallium, and Nitride determines the bandgap of the material, which directly defines the wavelength (color) of the emitted light. A higher indium content generally shifts the emission towards longer wavelengths (e.g., green, yellow, red), though green InGaN LEDs represent a significant technical achievement due to material challenges. The chip is encapsulated in a plastic package that includes a lens to shape the light output and protect the semiconductor die.

14. Industry Trends

The market for SMD LEDs continues to evolve with several key trends:

• Increased Efficiency (lm/W): Ongoing material and packaging research aims to extract more light (lumens) from the same electrical input power (watts), reducing energy consumption and thermal load.
• Miniaturization: Packages are becoming smaller (e.g., 0201, 01005 metric sizes) to enable higher-density board designs and new applications in ultra-compact devices.
• Improved Color Consistency & Binning: Advances in epitaxial growth and manufacturing control lead to tighter performance distributions, reducing the need for extensive binning and simplifying supply chains for color-critical applications.
• Integration: There is a trend towards integrating multiple LED chips (RGB, RGBW) into a single package or combining LEDs with drivers and control ICs to create "smart" lighting modules.
• Reliability & Lifetime: Focus on improving performance under high-temperature and high-current conditions to meet the demands of automotive, industrial, and outdoor lighting applications.

The component described in this datasheet represents a mature, reliable, and widely adopted solution within this evolving landscape.