LTW-C230DS2 Reverse Mount SMD LED Datasheet - InGaN White - 2.6-3.1V - 72mW - English Technical Document

1. Product Overview

The LTW-C230DS2 is a surface-mount device (SMD) light-emitting diode (LED) designed for reverse mounting applications. It utilizes an Ultra Bright InGaN (Indium Gallium Nitride) chip to produce white light. This component is packaged in industry-standard 8mm tape on 7-inch diameter reels, making it fully compatible with automated pick-and-place assembly equipment and high-volume production lines. As a green product, it complies with the Restriction of Hazardous Substances (RoHS) directive.

The primary design advantage of this LED is its reverse-mount configuration, which allows for innovative lighting designs where the LED is mounted on the opposite side of the PCB from the primary components. Its compatibility with infrared (IR) reflow soldering processes ensures it can be integrated using standard surface-mount technology (SMT) workflows without requiring special handling or soldering techniques.

2. Technical Parameter Deep-Dive

2.1 Absolute Maximum Ratings

The device's operational limits are defined at an ambient temperature (Ta) of 25°C. Exceeding these ratings may cause permanent damage.

• Power Dissipation (Pd): 72 mW. This is the maximum amount of power the LED package can dissipate as heat without degradation.
• Peak Forward Current (IFP): 100 mA. This is permissible only under pulsed conditions with a 1/10 duty cycle and a 0.1ms pulse width to prevent overheating.
• Continuous DC Forward Current (IF): 20 mA. This is the recommended maximum current for continuous operation.
• Operating Temperature Range: -30°C to +85°C. The device is guaranteed to function within this ambient temperature range.
• Storage Temperature Range: -55°C to +105°C.
• Infrared Reflow Condition: Withstands 260°C peak temperature for 10 seconds, aligning with common lead-free solder profiles.

Critical Note: The device is not designed for operation under reverse voltage bias. Applying a reverse voltage continuously is prohibited.

2.2 Electro-Optical Characteristics

Key performance parameters are measured at Ta=25°C and a standard test current (IF) of 2 mA.

• Luminous Intensity (Iv): Ranges from 18.0 mcd (minimum) to 45.0 mcd (typical). This is the perceived brightness of the light source as measured by a sensor filtered to match the human eye's photopic response (CIE curve).
• Viewing Angle (2θ1/2): 130 degrees. This wide viewing angle indicates a diffuse light emission pattern, suitable for area illumination rather than focused beams.
• Chromaticity Coordinates (x, y): The color point is defined within a specific region on the CIE 1931 chromaticity diagram. Typical values are x=0.294, y=0.286. Tolerance must be considered per the binning system.
• Forward Voltage (VF): Ranges from 2.6V (minimum) to 3.1V (maximum) at IF=2mA. This parameter is crucial for driver circuit design.
• Reverse Current (IR): Maximum 10 μA when a reverse voltage (VR) of 5V is applied. This test is for characterization only; the device must not be operated in reverse bias.

3. Binning System Explanation

To ensure color and brightness consistency in production, LEDs are sorted into bins based on measured parameters. The LTW-C230DS2 uses a three-dimensional binning system.

3.1 Forward Voltage (VF) Binning

LEDs are categorized into bins (A10, B10, B11, 12, 13) based on their forward voltage drop at 2 mA. Each bin has a range of 0.1V (e.g., B10: 2.70V to 2.80V). A tolerance of ±0.1V applies to each bin. This allows designers to select LEDs with tighter VF matching for current-sharing applications.

3.2 Luminous Intensity (IV) Binning

LEDs are sorted into brightness bins (M, N). Bin M covers 18-28 mcd, and Bin N covers 28-45 mcd at IF=2mA. A tolerance of ±15% applies to each bin. This bin code is marked on the packing bag for identification.

3.3 Hue (Color) Binning

The white color point is defined by chromaticity coordinates (x, y) on the CIE 1931 diagram. LEDs are binned into four quadrants: S1, S2, S3, and S4. Each bin defines a specific parallelogram area on the color chart. A tolerance of ±0.01 applies to each coordinate within a bin. This system ensures the white light emitted falls within a predictable and consistent color region.

4. Performance Curve Analysis

The datasheet references typical performance curves which illustrate the relationship between key parameters. While specific graphs are not detailed in the provided text, standard LED curves would typically include:

• Relative Luminous Intensity vs. Forward Current: Shows how light output increases with current, typically in a non-linear fashion, eventually saturating.
• Forward Voltage vs. Forward Current: Demonstrates the diode's I-V characteristic, showing the exponential relationship and the turn-on voltage.
• Relative Luminous Intensity vs. Ambient Temperature: Illustrates the decrease in light output as the junction temperature rises, a critical factor for thermal management.
• Viewing Angle Pattern: A polar plot showing the angular distribution of light intensity.

These curves are essential for predicting real-world performance under different operating conditions beyond the standard test point.

5. Mechanical and Packaging Information

5.1 Package Dimensions

The LED conforms to EIA standard package dimensions. All critical mechanical dimensions are provided in the datasheet drawings (not fully detailed in the provided text but typically include length, width, height, and pad spacing). Tolerances are generally ±0.10 mm unless otherwise specified. The lens color is yellow.

5.2 Soldering Pad Layout

Recommended soldering pad dimensions are provided to ensure proper mechanical attachment and thermal dissipation during the reflow process. Following these guidelines prevents tombstoning and ensures reliable solder joints.

5.3 Tape and Reel Specifications

The component is supplied in embossed carrier tape with a protective cover tape, wound onto 7-inch (178mm) diameter reels. Standard reel quantity is 3000 pieces. Packaging follows ANSI/EIA-481 specifications. Key notes include: empty pockets are sealed, a minimum pack quantity of 500 pieces for remainders, and a maximum of two consecutive missing components allowed per reel.

6. Assembly and Handling Guidelines

6.1 Soldering Process

The device is fully compatible with infrared (IR) reflow soldering. A recommended profile is suggested:

• Pre-heat: 150-200°C.
• Pre-heat Time: Maximum 120 seconds.
• Peak Temperature: Maximum 260°C.
• Time at Peak: Maximum 10 seconds (reflow should not be performed more than twice).

For manual rework with a soldering iron, the tip temperature should not exceed 300°C, and contact time should be limited to 3 seconds for a single operation only. The actual profile must be characterized for the specific PCB design, solder paste, and oven used.

6.2 Cleaning

If cleaning is necessary after soldering, only specified solvents should be used. Unspecified chemicals may damage the LED package. Acceptable methods include immersing the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute.

6.3 Storage and Moisture Sensitivity

LEDs are moisture-sensitive devices (MSL 2a).

• Sealed Package: Store at ≤30°C and ≤90% RH. Use within one year.
• Opened Package: Store at ≤30°C and ≤60% RH. Components should be IR-reflowed within 672 hours (28 days) of exposure. For storage beyond one week out of the original bag, store in a sealed container with desiccant or in a nitrogen desiccator. Components stored opened for more than a week require baking at approximately 60°C for at least 20 hours before assembly to remove absorbed moisture and prevent \"popcorning\" during reflow.

6.4 Electrostatic Discharge (ESD) Precautions

LEDs are susceptible to damage from static electricity and electrical surges. It is recommended to use a wrist strap or anti-static gloves when handling. All equipment, including workstations and machinery, must be properly grounded.

7. Application Notes and Design Considerations

7.1 Typical Applications

This LED is intended for general-purpose lighting and indication in consumer electronics, office equipment, communication devices, and household appliances. Its reverse-mount capability enables unique backlighting solutions for keyboards, panels, and displays where the light source needs to be hidden or mounted on the secondary side of the PCB.

7.2 Design Considerations

• Current Limiting: Always use a series current-limiting resistor or a constant-current driver. Do not connect directly to a voltage source. The maximum continuous DC current is 20 mA.
• Thermal Management: While power dissipation is low (72mW), ensuring adequate PCB copper area for the solder pads helps dissipate heat, maintaining light output and longevity.
• Optical Design: The 130-degree viewing angle provides wide, diffuse illumination. For more focused light, secondary optics (lenses or light guides) would be required.
• Binning Selection: For applications requiring uniform color and brightness, specify a single bin or a tight combination of bins from the manufacturer.

7.3 Application Limitations

Consult the manufacturer for applications requiring high reliability, especially where failure could risk life or health (e.g., aviation, medical, transportation safety systems). This product is designed for standard commercial and industrial environments.

8. Frequently Asked Questions (FAQ)

Q: What is the difference between a reverse mount LED and a standard top-view SMD LED?
A: A reverse mount LED is designed to be installed on the opposite side of the PCB, with its light emitting surface facing down towards the board. It then shines through a hole or aperture in the PCB. A standard top-view LED emits light perpendicularly away from the board surface it's mounted on.

Q: Can I drive this LED at 20mA continuously?
A: Yes, 20mA is the maximum rated continuous DC forward current. For optimal lifetime and reliability, driving it at a lower current (e.g., 10-15mA) is often recommended, as it reduces heat generation.

Q: Why is the luminous intensity specified at such a low current (2mA)?
A> 2mA is a common standard test condition for characterizing LED brightness at a low power level, allowing for easier comparison between different LED models and consistent binning. The brightness will be proportionally higher at the maximum operating current of 20mA.

Q: How do I interpret the chromaticity coordinates (x=0.294, y=0.286)?
A> These coordinates plot a point on the CIE 1931 color space chart. This specific point falls within the \"white\" region. The exact perceived white (e.g., cool white, neutral white) depends on the precise location. The binning system (S1-S4) groups LEDs with closely matched coordinates to ensure color consistency.

Q: Is a heat sink required for this LED?
A> Due to its low power dissipation (72mW), a dedicated heat sink is typically not required. However, good PCB layout practices, such as using sufficient copper for the thermal pads, are essential to conduct heat away from the LED junction, especially in high ambient temperature environments or when driven at maximum current.