LTST-C230TBKT-5A SMD LED Datasheet - Reverse Mount - Blue (InGaN) - 2.65-3.15V - 76mW - English Technical Document

1. Product Overview

The LTST-C230TBKT-5A is a surface-mount device (SMD) light-emitting diode (LED) designed for modern electronic assembly processes. Its core component is an ultra-bright indium gallium nitride (InGaN) semiconductor chip, which emits blue light. A key distinguishing feature of this component is its reverse mount design, meaning the primary light emission is through the substrate side of the package. This is indicated by the "Water Clear" lens description, which typically allows for a wider or more specific viewing angle compared to diffused lenses. The device is packaged on 8mm tape wound onto 7-inch reels, making it fully compatible with high-speed automated pick-and-place equipment used in volume manufacturing.

The product is classified as a green product, meaning it complies with the Restriction of Hazardous Substances (RoHS) directive. It is also designed to be integrated circuit (IC) compatible and can withstand standard infrared (IR) reflow soldering processes, which are essential for lead-free (Pb-free) printed circuit board (PCB) assembly.

2. Technical Parameters: In-Depth Objective Interpretation

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. They are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): 76 mW. This is the maximum amount of power the LED can dissipate as heat without degrading its performance or lifespan. Exceeding this limit, especially at higher ambient temperatures, can lead to accelerated lumen depreciation and potential failure.
• Peak Forward Current (I_F(PEAK)): 100 mA. This is the maximum allowable instantaneous forward current, but only under pulsed conditions with a strict 1/10 duty cycle and a pulse width of 0.1ms. It is not for continuous operation.
• DC Forward Current (I_F): 20 mA. This is the recommended maximum continuous forward current for reliable long-term operation. Most electrical and optical characteristics are measured at a standard test current of 5 mA.
• Operating & Storage Temperature: The device can function in environments from -20°C to +80°C and can be stored from -30°C to +85°C.
• Infrared Soldering Condition: The package can withstand a peak temperature of 260°C for up to 10 seconds during reflow soldering, which aligns with common Pb-free process requirements.

2.2 Electro-Optical Characteristics

These parameters are measured at Ta=25°C and I_F=5 mA, unless otherwise noted, and define the performance of the LED.

• Luminous Intensity (I_V): Ranges from a minimum of 11.2 millicandelas (mcd) to a maximum of 45.0 mcd. The typical value is not specified, indicating performance is managed through binning (see Section 3). Intensity is 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 luminous intensity drops to half of its value measured on-axis (0 degrees). A wide viewing angle like this is characteristic of reverse mount or side-view LEDs and is suitable for backlighting and indicator applications requiring wide illumination.
• Peak Wavelength (λ_P): 468 nanometers (nm). This is the wavelength at which the spectral power output is highest.
• Dominant Wavelength (λ_d): Ranges from 465.0 nm to 476.5 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 more relevant parameter for color specification than peak wavelength.
• Spectral Line Half-Width (Δλ): 25 nm. This indicates the spectral purity or bandwidth of the emitted light, measured as the width at half the maximum intensity.
• Forward Voltage (V_F): Ranges from 2.65V to 3.15V at 5 mA. This is the voltage drop across the LED when it is conducting current. It is a critical parameter for driver circuit design.
• Reverse Current (I_R): Maximum 10 μA at a reverse voltage (V_R) of 5V. This LED is not designed for reverse bias operation; this parameter is for leakage current testing only. Applying reverse voltage in-circuit can damage the device.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins. The LTST-C230TBKT-5A uses a three-dimensional binning system.

3.1 Forward Voltage Binning

Bins are labeled 1 through 5, each covering a 0.1V range from 2.65V to 3.15V at 5 mA. Tolerance within each bin is ±0.1V. This allows designers to select LEDs with similar V_F for current-sharing in parallel arrays.

3.2 Luminous Intensity Binning

Bins are labeled L1, L2, M1, M2, N1, N2, with minimum intensities ranging from 11.2 mcd to 35.5 mcd. Tolerance on each bin is ±15%. This enables selection based on brightness requirements for the application.

3.3 Dominant Wavelength Binning

Two bins are defined: AC (465.0-470.0 nm) and AD (470.0-476.5 nm). Tolerance is ±1 nm. This ensures color consistency within a batch of LEDs, which is crucial for applications like multi-segment displays or color-mixed backlighting.

4. Performance Curve Analysis

While specific graphical data is referenced but not provided in the text extract, typical curves for such LEDs would include:

• Relative Luminous Intensity vs. Forward Current (I_V vs. I_F): Shows how light output increases with current, typically in a sub-linear manner at higher currents due to heating and efficiency droop.
• Forward Voltage vs. Forward Current (V_F vs. I_F): Demonstrates the diode's exponential I-V characteristic. The voltage increases with current and decreases with rising junction temperature.
• Relative Luminous Intensity vs. Ambient Temperature: Illustrates the thermal quenching effect, where light output decreases as the ambient (and thus junction) temperature rises. Proper thermal management is key to maintaining stable brightness.
• Spectral Power Distribution: A plot showing the intensity of emitted light across the wavelength spectrum, centered around the peak wavelength of 468 nm with a characteristic half-width.

5. Mechanical and Package Information

5.1 Package Dimensions

The LED conforms to an EIA standard package outline. Key dimensional tolerances are ±0.10 mm unless otherwise specified. The exact footprint and component height are defined in the dimensional drawings referenced in the datasheet.

5.2 Polarity Identification and Pad Design

For reverse mount LEDs, polarity identification (cathode/anode) is typically marked on the top of the package or indicated by a specific pad shape or size difference on the footprint drawing. The datasheet includes suggested soldering pad dimensions to ensure a reliable solder joint and proper alignment during reflow. Following these recommendations is critical for mechanical stability and thermal performance.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

A suggested infrared (IR) reflow profile for Pb-free processes is provided. Key parameters include a pre-heat zone (150-200°C), a controlled ramp to a peak temperature not exceeding 260°C, and a time above liquidus (TAL) that ensures proper solder joint formation without exposing the LED to excessive thermal stress. The component can withstand this peak temperature for a maximum of 10 seconds. The profile is based on JEDEC standards to ensure reliability.

6.2 Manual Soldering

If manual soldering with an iron is necessary, the tip temperature should not exceed 300°C, and contact time should be limited to a maximum of 3 seconds for a single operation only.

6.3 Cleaning

If cleaning after soldering is required, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute is recommended. Unspecified chemicals may damage the plastic package or lens.

6.4 Storage and Handling

• ESD Precautions: LEDs are sensitive to electrostatic discharge (ESD). Handling should involve the use of wrist straps, anti-static gloves, and properly grounded equipment.
• Moisture Sensitivity: The package is moisture-sensitive. When sealed with desiccant, it should be stored at ≤30°C and ≤90% RH and used within one year. Once opened, the storage environment should not exceed 30°C and 60% RH. Components exposed beyond 672 hours (MSL 2a level) should be baked at approximately 60°C for at least 20 hours before soldering to prevent "popcorning" during reflow.

7. Packaging and Ordering Information

The standard packaging is 8mm embossed carrier tape on 7-inch (178mm) diameter reels. Each reel contains 3000 pieces. Empty pockets in the tape are sealed with a top cover tape. The packaging follows ANSI/EIA-481 specifications. For quantities less than a full reel, a minimum packing quantity of 500 pieces applies for remainders.

8. Application Suggestions

8.1 Typical Application Scenarios

The reverse mount design and wide viewing angle make this LED suitable for:

• Edge-lit Backlighting: For LCD displays in consumer electronics, appliances, and automotive interiors, where light is injected from the side into a light guide plate.
• Status Indicators: On front panels of equipment where a wide viewing angle is beneficial.
• Decorative Lighting: In signage or accent lighting where side emission is required.

8.2 Design Considerations

• Current Driving: Use a constant current driver or a current-limiting resistor in series with the LED to maintain stable brightness and prevent thermal runaway. The standard operating point is 5-20 mA DC.
• Thermal Management: Although power dissipation is low, ensuring a good thermal path from the LED pads to the PCB copper helps maintain performance and longevity, especially at higher ambient temperatures or drive currents.
• Optical Design: The water clear lens produces a more focused beam pattern compared to a diffused lens. Consider this in light guide or diffuser design for backlighting applications.

9. Technical Comparison and Differentiation

The primary differentiation of this LED lies in its reverse mount architecture. Unlike top-emitting LEDs, light is emitted through the substrate, which often allows for a lower profile installation and a very wide viewing angle ideal for side-firing into light guides. The use of an InGaN chip provides high efficiency and brightness in the blue spectrum. Compliance with automatic placement and IR reflow standards makes it a drop-in component for modern, high-volume SMT assembly lines, distinguishing it from older through-hole or manual-assembly LEDs.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED at 20 mA continuously?
A: Yes, 20 mA is the maximum recommended DC forward current. For optimal longevity and to account for thermal effects, operating at or below this value, such as the standard test current of 5 mA, is common.

Q: What does the bin code in the part number (e.g., -5A) signify?
A: While not explicitly detailed in the extract, suffixes like "-5A" often indicate specific bin combinations for forward voltage, intensity, and/or wavelength as per the bin code lists provided. This allows precise selection for application needs.

Q: Is a heatsink required for this LED?
A: For operation at or below 20 mA in typical ambient conditions, the PCB copper itself usually provides sufficient heatsinking. For high ambient temperatures or if driven at the absolute maximum ratings, enhancing the thermal design of the PCB footprint is advisable.

Q: Can I use this for automotive exterior lighting?
A: The datasheet states the LED is intended for ordinary electronic equipment. For applications with exceptional reliability requirements like automotive exterior lighting, consultation with the manufacturer is necessary to verify suitability and obtain specific automotive-grade qualifications.

11. Practical Use Case Example

Design Case: Backlight for a Small Instrument Panel Display
A designer needs to backlight a 2-inch monochrome LCD with even illumination. They choose the LTST-C230TBKT-5A for its side-emitting property. Four LEDs are placed along one edge of a acrylic light guide plate (LGP). The LEDs are driven in series with a constant current driver set to 15 mA per LED, ensuring uniform current and brightness. The wide 130-degree viewing angle efficiently couples light into the LGP. The designer selects LEDs from the same intensity bin (e.g., M1) and wavelength bin (e.g., AC) to guarantee consistent brightness and color across the display. The PCB layout follows the suggested pad dimensions and includes thermal relief connections to a ground plane for heat dissipation.

12. Principle Introduction

Light emission in this LED is based on electroluminescence in a semiconductor p-n junction made of InGaN materials. When a forward voltage is applied, electrons and holes are injected into the active region where they recombine. In InGaN semiconductors, this recombination releases energy primarily in the form of blue photons. The specific wavelength (blue color) is determined by the bandgap energy of the InGaN alloy. The "reverse mount" design means the chip is mounted in a way that the light-generating active layer emits downwards through the transparent substrate of the chip, which is then shaped and directed by the water-clear epoxy lens of the package.

13. Development Trends

The trend in SMD LEDs like this one continues towards higher luminous efficacy (more light output per watt of electrical input), improved color consistency through tighter binning, and enhanced reliability under higher temperature and humidity conditions. Packaging technology is evolving to allow for even smaller footprints while maintaining or increasing light output. There is also a strong drive towards broader adoption of lead-free and halogen-free materials to meet evolving environmental regulations globally. The integration of LEDs into automated assembly and inspection processes remains a key focus, ensuring compatibility with Industry 4.0 smart manufacturing lines.