LTW-C230DS Reverse Mount SMD LED Datasheet - InGaN White - 20mA - 72mW - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a high-brightness, reverse mount surface-mount device (SMD) LED. The component is designed for automated assembly processes and is compliant with RoHS and green product standards. Its primary application is in backlighting and indicator functions within consumer electronics, office equipment, and communication devices where reliable, compact illumination is required.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The device is rated for operation within strict environmental and electrical limits to ensure long-term reliability. The absolute maximum ratings define the thresholds beyond which permanent damage may occur.

• Power Dissipation: 72 mW. This is the maximum amount of power the LED package can dissipate as heat under any operating condition.
• Peak Forward Current: 100 mA. This current is permissible only under pulsed conditions with a 1/10 duty cycle and a 0.1ms pulse width, typically for brief testing or specific drive scenarios.
• DC Forward Current: 20 mA. This is the recommended continuous forward current for standard operation, balancing brightness and longevity.
• Operating Temperature Range: -30°C to +85°C. The LED is designed to function correctly within this ambient temperature range.
• Storage Temperature Range: -55°C to +105°C. The device can be stored without degradation within these limits.
• Infrared Soldering Condition: 260°C for 10 seconds. This defines the peak temperature and duration the LED can withstand during a standard IR reflow soldering process.

Critical Note: The device is not designed for operation under reverse voltage bias. Applying a continuous reverse voltage can cause immediate failure.

2.2 Electrical & Optical Characteristics

These parameters are measured at an ambient temperature (Ta) of 25°C and define the typical performance of the LED.

• Luminous Intensity (Iv): 180 - 450 mcd (millicandela) at a forward current (IF) of 20 mA. The actual value for a specific unit falls within this range and is classified by a bin code.
• Viewing Angle (2θ1/2): 130 degrees. This wide viewing angle indicates a Lambertian or near-Lambertian emission pattern, suitable for area illumination.
• Chromaticity Coordinates (x, y): Typical values are x=0.294, y=0.286 (measured at IF=20mA). These coordinates on the CIE 1931 chromaticity diagram define the white point of the LED. A tolerance of ±0.02 is applied to these coordinates.
• Forward Voltage (VF): 2.8 - 3.6 Volts at IF=20mA. The voltage drop across the LED when operating, which is used for drive circuit design.
• Reverse Current (IR): 10 μA (max) at a Reverse Voltage (VR) of 5V. This test condition is for characterization only; the device must not be operated in reverse bias.

Measurement Notes: Luminous intensity is measured using equipment calibrated to the CIE photopic eye-response curve. Electrostatic discharge (ESD) precautions are mandatory during handling to prevent damage.

3. Binning System Explanation

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

3.1 Forward Voltage (VF) Bins

LEDs are categorized based on their forward voltage at 20mA. Each bin has a tolerance of ±0.1V.

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

3.2 Luminous Intensity (IV) Bins

LEDs are sorted by their minimum luminous output, with a tolerance of ±15% within each bin.

• S Bin: 180 mcd - 280 mcd
• T Bin: 280 mcd - 450 mcd

3.3 Hue (Color) Bins

The white color point is defined within specific quadrilaterals on the CIE 1931 diagram, labeled S1, S2, S3, and S4. Each bin has precise (x, y) coordinate boundaries with a tolerance of ±0.01. This system ensures color uniformity across multiple LEDs in an assembly.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Fig.6 for viewing angle), their interpretation is crucial for design.

• IV Curve (Current vs. Voltage): This curve is non-linear. The forward voltage (VF) specified is at the typical operating current (20mA). Driving the LED at a lower current will result in a lower VF, and vice versa. This is critical for designing constant-current drivers.
• Luminous Intensity vs. Current (LI-I Curve): The light output is approximately proportional to the forward current up to a point. Exceeding the maximum DC current (20mA) may increase output temporarily but will drastically reduce lifespan and can cause catastrophic failure.
• Temperature Dependence: LED performance is temperature-sensitive. Typically, forward voltage decreases with increasing junction temperature, while luminous efficacy (light output per electrical watt) also decreases. The specified parameters are at 25°C; derating may be necessary for high-temperature environments.

5. Mechanical & Packaging Information

5.1 Package Dimensions

The LED conforms to an EIA standard package outline for reverse-mount components. Key dimensional tolerances are ±0.10mm unless otherwise specified. The package features a yellow lens which houses the InGaN semiconductor die.

5.2 Polarity Identification

As a reverse mount component, the polarity (anode/cathode) is indicated by the package structure or marking on the tape and reel. Correct orientation during placement is essential for circuit function.

5.3 Suggested Soldering Pad Layout

A recommended land pattern (footprint) is provided to ensure proper solder joint formation, mechanical stability, and thermal management during reflow soldering. Adhering to this layout minimizes tombstoning and improves reliability.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profile

The LED is compatible with infrared (IR) reflow processes. A recommended profile is provided, adhering to JEDEC standards.

• Pre-heat: 150°C to 200°C.
• Pre-heat Time: Maximum 120 seconds to allow for uniform heating and paste activation.
• Peak Temperature: Maximum 260°C.
• Time Above Liquidus (at peak): Maximum 10 seconds. The component should not be subjected to this peak temperature more than twice.

Note: The actual profile must be characterized for the specific PCB design, solder paste, and oven used.

6.2 Hand Soldering (If Necessary)

If manual soldering is required, extreme care must be taken:

• Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per pad.
• Frequency: Only one soldering cycle is permitted to avoid thermal damage to the epoxy lens and semiconductor die.

6.3 Storage Conditions

Moisture sensitivity is a critical factor for SMD components.

• Sealed Package: Store at ≤30°C and ≤90% RH. Use within one year of the pack date.
• Opened Package: Store at ≤30°C and ≤60% RH. Components should be IR-reflowed within 672 hours (28 days) of exposure. For longer storage, use a sealed container with desiccant or a nitrogen desiccator. Components exposed for over one week should be baked at 60°C for at least 20 hours before soldering.

6.4 Cleaning

Only specified cleaning agents should be used to avoid damaging the LED package or lens.

• Recommended Solvents: Ethyl alcohol or isopropyl alcohol.
• Procedure: Immerse at normal temperature for less than one minute if cleaning is absolutely necessary.
• Avoid: Unspecified chemical liquids.

7. Packaging & Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied in industry-standard packaging for automated pick-and-place machines.

• Carrier Tape: 8mm wide.
• Reel Diameter: 7 inches.
• Quantity per Reel: 3000 pieces.
• Minimum Order Quantity (for remainders): 500 pieces.
• Pocket Coverage: Empty pockets are sealed with cover tape.
• Missing Lamps: Maximum of two consecutive missing LEDs allowed, per ANSI/EIA 481 specifications.

8. Application Notes & Design Considerations

8.1 Intended Use

This LED is designed for ordinary electronic equipment including office automation devices, communication equipment, and household appliances. It is not rated for safety-critical applications where failure could jeopardize life or health (e.g., aviation, medical life-support). For such applications, consultation with the manufacturer for high-reliability grades is mandatory.

8.2 Circuit Design

• Current Limiting: Always use a series resistor or a constant-current driver to limit the forward current to 20mA DC or less. Do not connect directly to a voltage source.
• Thermal Management: While the power dissipation is low (72mW), ensuring adequate PCB copper area around the solder pads helps dissipate heat, especially in high ambient temperatures or when driven at the maximum current.
• ESD Protection: Incorporate ESD protection on input lines if the LED is in an exposed location (e.g., a front panel indicator). Always follow ESD-safe handling procedures during assembly.

8.3 Optical Design

• The wide 130-degree viewing angle provides good off-axis visibility, making it suitable for status indicators that need to be seen from various angles.
• For backlighting applications, light guides or diffusers may be necessary to achieve uniform illumination across a surface.

9. Technical Comparison & Differentiation

The key differentiating features of this component are its reverse mount design and InGaN-based white emission.

• Reverse Mount vs. Top-View: Reverse mount (or bottom-view) LEDs emit light through the substrate and out the side of the package opposite the mounting surface. This is ideal for applications where the LED is mounted on the bottom side of a PCB and light is required to shine through a hole or light guide, creating a sleek, flush appearance.
• InGaN White Technology: InGaN (Indium Gallium Nitride) semiconductors are used to produce blue light. White light is typically achieved by coating the blue die with a yellow phosphor. This technology offers high efficiency, good color rendering potential, and long lifetime compared to older technologies.
• RoHS & Green Compliance: The device is free of restricted hazardous substances like lead and mercury, making it suitable for global markets with environmental regulations.

10. Frequently Asked Questions (FAQ)

10.1 Can I drive this LED with a 3.3V supply without a resistor?

No. The forward voltage ranges from 2.8V to 3.6V. Connecting a 3.3V supply directly could result in a current exceeding 20mA for many units (especially those in the D7 or D8 voltage bins), leading to rapid degradation or failure. A current-limiting resistor or regulator is always required.

10.2 What does the bin code on the bag mean?

The bin code indicates the performance group for that specific batch of LEDs. It typically combines codes for Luminous Intensity (IV), Forward Voltage (VF), and Hue (Color). For example, a code might be "T-D8-S2," meaning it falls in the T brightness bin, D8 voltage bin, and S2 color bin. This allows for precise selection for color- or brightness-critical applications.

10.3 How do I interpret the Chromaticity Diagram and S1-S4 bins?

The CIE 1931 diagram is a color map. The (x, y) coordinates from the datasheet (e.g., 0.294, 0.286) plot a point representing the LED's white color. The S1-S4 bins are defined areas (quadrilaterals) on this map. All LEDs from a given bin will have color coordinates falling within its specific area, ensuring visual color matching between different units.

10.4 Why is storage humidity so important?

SMD packages can absorb moisture from the air. During the high-temperature reflow soldering process, this absorbed moisture can rapidly turn to steam, creating pressure inside the package. This can lead to "popcorning" – internal delamination or cracking of the epoxy lens or the die attach, resulting in immediate failure or reduced long-term reliability. The storage guidelines prevent excessive moisture absorption.

11. Practical Application Example

11.1 Designing a PCB Status Indicator

Scenario: A microcontroller-based board needs a power-on indicator. The LED will be mounted on the bottom side of the PCB, shining up through a small drilled hole.

1. Component Selection: Choose an LED from the "T" brightness bin for good visibility. For simple design, select a mid-range voltage bin like "D8" or "D9". Color bin can be standard unless specific white tone is critical.
2. Schematic Design: Connect the LED anode (via the current-limiting resistor) to a GPIO pin of the microcontroller configured as an output. Connect the LED cathode to ground. Include a footprint for the current-limiting resistor.
3. Current Limiting Resistor Calculation: Assuming a 3.3V microcontroller supply (Vcc), a typical VF of 3.2V (from D8 bin), and a desired IF of 15mA (for longer life and lower power).
   R = (Vcc - VF) / IF = (3.3V - 3.2V) / 0.015A = 6.67 Ω. Use the nearest standard value, e.g., 6.8 Ω. Verify power rating: P = I²R = (0.015)² * 6.8 = 0.00153W, so a standard 1/10W (0.1W) resistor is more than sufficient.
4. PCB Layout: Place the LED on the bottom layer. Use the recommended soldering pad dimensions from the datasheet. Ensure the hole in the top solder mask (for light emission) is aligned with the LED's emitting area. Provide some small thermal relief on the pads if connected to large ground/power planes.
5. Assembly: Follow the IR reflow profile guidelines. After assembly, visually inspect the solder joints.

12. Operating Principle

Light emission in this LED is based on electroluminescence in a semiconductor p-n junction made of InGaN materials. When a forward voltage exceeding the junction's built-in potential is applied, electrons from the n-type region and holes from the p-type region are injected into the active region. Here, they recombine, releasing energy in the form of photons. The specific composition of the InGaN layers determines the primary emission wavelength (blue). To produce white light, a portion of this blue light is absorbed by a cerium-doped yttrium aluminum garnet (YAG:Ce) phosphor coating on the die, which re-emits it as broad-spectrum yellow light. The mixture of the remaining blue light and the converted yellow light is perceived by the human eye as white.

13. Technology Trends

The solid-state lighting industry continues to evolve. General trends relevant to components like this include:

• Increased Efficiency (Lumens per Watt): Ongoing improvements in epitaxial growth, chip design, and phosphor technology drive higher light output for the same electrical input, reducing energy consumption.
• Improved Color Quality: Development of multi-phosphor blends and novel semiconductor structures (e.g., quantum dots) to achieve higher Color Rendering Index (CRI) values and more precise color tuning, moving beyond standard white points.
• Miniaturization: The drive for smaller, denser electronics pushes for LEDs in ever-smaller package footprints while maintaining or improving optical performance.
• Enhanced Reliability & Lifetime: Advancements in packaging materials, die attach methods, and phosphor stability are extending the operational lifetime and reliability of LEDs, especially under high-temperature and high-humidity conditions.
• Intelligent Integration: A growing trend is the integration of control circuitry (drivers, sensors) directly with the LED die or within the package, enabling smart lighting features.