LTW-327ZDSKG-5A Dual Color SMD LED Datasheet - Side Looking - White/Green - 5mA - English Technical Document

1. Product Overview

The LTW-327ZDSKG-5A is a dual-color, side-looking (right-angle) Surface Mount Device (SMD) LED. This component is specifically engineered for applications requiring illumination from the side of the package, making it an ideal choice for LCD panel backlighting systems, edge-lit panels, and other space-constrained lighting solutions where light needs to be directed laterally rather than perpendicularly from the board.

The device integrates two distinct semiconductor chips within a single package: an InGaN (Indium Gallium Nitride) chip for white light emission and an AlInGaP (Aluminum Indium Gallium Phosphide) chip for green light emission. This dual-chip configuration allows for color mixing or independent control of two light sources from one compact footprint. The package features a tin-plated lead frame for improved solderability and is supplied on 8mm tape mounted on 7-inch diameter reels, compatible with high-speed automated pick-and-place assembly equipment.

1.1 Core Features and Advantages

• Dual Color Source: Combines white and green LEDs in one EIA-standard package, saving board space and simplifying design.
• Right-Angle Emission: The side-looking design is optimized for directing light parallel to the PCB surface, crucial for edge-lighting applications.
• High Brightness: Utilizes advanced InGaN and AlInGaP chip technology to deliver high luminous intensity.
• Manufacturing Compatibility: Package is designed for compatibility with standard automated placement systems and infrared (IR) reflow soldering processes.
• Environmental Compliance: The product is compliant with the RoHS (Restriction of Hazardous Substances) directive.

2. Technical Specifications Deep Dive

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed and should be avoided in circuit design.

• Power Dissipation (Pd): White: 35 mW, Green: 48 mW. This is the maximum allowable power loss as heat.
• Peak Forward Current (I_FP): White: 50 mA, Green: 40 mA. This is the maximum pulsed current (1/10 duty cycle, 0.1ms pulse width) the LED can withstand momentarily.
• Continuous Forward Current (I_F): White: 10 mA, Green: 20 mA. This is the maximum recommended DC current for continuous operation at Ta=25°C.
• Temperature Ranges: Operating: -20°C to +80°C; Storage: -40°C to +85°C.
• Soldering Condition: Withstands infrared reflow soldering at 260°C peak temperature for 10 seconds.
• Electrostatic Discharge (ESD): Human Body Model (HBM) threshold is 2000V. Proper ESD handling precautions are mandatory.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at an ambient temperature (Ta) of 25°C and a forward current (I_F) of 5mA, unless otherwise specified.

• Luminous Intensity (I_V): A key measure of brightness.
  • White: Minimum 28.0 mcd, Typical value not specified, Maximum 112.0 mcd.
  • Green: Minimum 4.5 mcd, Typical value not specified, Maximum 18.0 mcd.
• Viewing Angle (2θ_1/2): Approximately 130 degrees for both colors, defining the angular spread of emitted light.
• Forward Voltage (V_F): The voltage drop across the LED when conducting.
  • White: Min 2.70V, Typ 3.00V, Max 3.15V.
  • Green: Min 1.70V, Typ 2.00V, Max 2.40V.
  The difference in V_F between colors is important for driver circuit design, especially if they are to be driven from a common current source.
• Green Chip Spectral Properties (at I_F=5mA):
  • Peak Wavelength (λ_P): Typically 575 nm.
  • Dominant Wavelength (λ_d): Typically 570 nm.
  • Spectral Half-Width (Δλ): Typically 20 nm.
  • Chromaticity Coordinates (x, y): Typically (0.3, 0.3) on the CIE 1931 diagram.
• Reverse Current (I_R): Maximum 100 µA at a Reverse Voltage (V_R) of 5V. The device is not designed for reverse bias operation.

3. Binning System Explanation

The LEDs are sorted into performance bins to ensure consistency. The classification code is marked on the packing bag.

3.1 Luminous Intensity (I_V) Binning

LEDs are grouped based on their measured luminous output at 5mA.

• White LED Bins:
  • N: 28.0 - 45.0 mcd
  • P: 45.0 - 71.0 mcd
  • Q: 71.0 - 112.0 mcd
• Green LED Bins:
  • J: 4.5 - 7.1 mcd
  • K: 7.1 - 11.2 mcd
  • L: 11.2 - 18.0 mcd

Tolerance for each luminous intensity bin is +/- 15%.

3.2 Hue (Chromaticity) Binning for Green LED

The green LEDs are also binned according to their color point on the CIE 1931 chromaticity diagram, defined by coordinates (x, y). Six bins (S1 through S6) are specified with precise coordinate boundaries. The tolerance for each hue bin is +/- 0.01 in both x and y coordinates. This ensures tight color consistency for applications where precise green color is critical.

4. Performance Curve Analysis

The datasheet references typical characteristic curves which are essential for understanding device behavior under different conditions. While the specific graphs are not reproduced in the text, they typically include:

• Relative Luminous Intensity vs. Forward Current: Shows how brightness increases with current, up to the maximum ratings.
• Forward Voltage vs. Forward Current: Illustrates the diode's I-V characteristic.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the thermal derating of light output, which is crucial for thermal management in the application.
• Spectral Power Distribution: For the green LED, showing the intensity of light emitted at each wavelength, centered around the peak wavelength of ~575 nm.

Designers should use these curves to select appropriate operating points and understand performance trade-offs, especially regarding efficiency and thermal effects.

5. Mechanical & Package Information

5.1 Pin Assignment and Polarity

The part number LTW-327ZDSKG-5A has a yellow lens. The pin assignment is as follows:

• Anode 1 (A1): Connected to the AlInGaP Green chip.
• Anode 2 (A2): Connected to the InGaN White chip.

The common cathode is implied but not explicitly labeled in the provided text. The mechanical drawing would show the cathode pad. Correct polarity is essential to prevent damage.

5.2 Package Dimensions and Tolerances

The device conforms to an EIA standard package outline for side-looking LEDs. All dimensions are in millimeters, with a standard tolerance of ±0.10 mm unless otherwise noted on the detailed package drawing. The datasheet includes suggested soldering pad dimensions and orientation to ensure proper mechanical alignment and solder joint reliability during reflow.

6. Assembly, Soldering & Handling Guidelines

6.1 Soldering Process

The LED is compatible with infrared (IR) reflow soldering processes. A recommended profile is suggested, with a peak temperature of 260°C sustained for 10 seconds. Adhering to this profile is critical to prevent thermal damage to the LED package or the internal wire bonds.

6.2 Cleaning

If cleaning after soldering is necessary, only specified chemicals should be used. Unspecified chemicals may damage the plastic package. The recommended method is to immerse the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute.

6.3 Storage and Moisture Sensitivity

LEDs are moisture-sensitive devices. Specific storage conditions are mandated:

• Sealed Package: Store at ≤30°C and ≤90% Relative Humidity (RH). Use within one year.
• Opened Package: Storage ambient must not exceed 30°C or 60% RH. It is recommended to complete IR reflow within one week of opening.
• Extended Storage (Opened): Store in a sealed container with desiccant or in a nitrogen desiccator.
• Rebaking: If stored out of the original packaging for more than one week, a bake at approximately 60°C for at least 20 hours is required before soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

6.4 Electrostatic Discharge (ESD) Precautions

The device has an ESD threshold of 2000V (HBM). To prevent damage from static electricity, it is mandatory to use proper ESD controls: wrist straps, anti-static gloves, and ensuring all equipment and workstations are properly grounded.

7. Packaging and Ordering

7.1 Tape and Reel Specifications

The LEDs are supplied in industry-standard embossed carrier tape, 8mm in width, with a top cover tape. The tape is wound onto 7-inch (178mm) diameter reels.

• Quantity per Reel: 3000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Packaging Standards: Conforms to ANSI/EIA-481 specifications.
• Quality: The maximum number of consecutive missing components (empty pockets) in the tape is two.

Detailed mechanical drawings for the tape pocket dimensions, reel hub, and flange are provided for automated handling equipment setup.

8. Application Notes and Design Considerations

8.1 Target Applications

The primary application for this side-looking, dual-color LED is LCD backlighting, particularly for small to medium-sized displays in consumer electronics, industrial panels, and automotive interiors. The right-angle design allows it to be placed at the edge of a light guide plate, efficiently coupling light into the panel. Other potential uses include status indicators in tight spaces, decorative edge lighting, and backlighting for keypads or symbols.

8.2 Circuit Design Considerations

• Current Limiting: Always use a series resistor or constant current driver to limit the forward current to the recommended DC value (10mA for white, 20mA for green) or below. Exceeding I_F reduces lifetime and can cause immediate failure.
• Independent Control: The two anodes allow the white and green LEDs to be driven independently. This enables color mixing (to create shades of blue-green or aqua) or separate signaling functions.
• Thermal Management: Although power dissipation is low, ensuring adequate PCB copper area or thermal vias for the cathode pad can help maintain lower junction temperature, preserving light output and longevity, especially in high ambient temperature environments.
• Voltage Supply: Account for the different forward voltages when designing the drive circuitry. A single current source with a resistor for each color may be sufficient, but voltage headroom must be checked for both.

8.3 Reliability and Lifetime

LED lifetime is strongly influenced by operating conditions. Key factors include:

• Drive Current: Operating below the maximum rated current significantly extends operational life.
• Junction Temperature (T_j): High T_j accelerates lumen depreciation and can shift chromaticity. Effective heat sinking via the PCB is crucial.
• Environmental Sealing: The plastic package provides basic protection, but exposure to harsh chemicals, UV radiation, or extreme humidity outside the specified ranges should be avoided.

9. Technical Comparison and Differentiation

The LTW-327ZDSKG-5A differentiates itself through its specific combination of features:

• vs. Single-Color Side-Looking LEDs: Offers design flexibility by providing two colors in one package, reducing part count and board space versus using two separate single-color LEDs.
• vs. Top-Emitting LEDs: The right-angle emission profile is its defining characteristic, enabling entirely different optical designs focused on edge-lighting rather than direct illumination.
• vs. Other Dual-Color LEDs: The use of InGaN for white and AlInGaP for green represents a combination chosen for efficiency and color quality. The specific binning structure for both intensity and hue (for green) indicates a focus on color consistency for display applications.

10. Frequently Asked Questions (FAQ)

Q1: Can I drive the white and green LEDs simultaneously at their maximum DC current?
A1: Yes, but you must consider the total power dissipation. Simultaneous operation at I_F(White)=10mA (V_F~3.0V, P=30mW) and I_F(Green)=20mA (V_F~2.0V, P=40mW) results in a combined ~70mW. Ensure the application's thermal environment can handle this combined heat load without exceeding the maximum junction temperature.

Q2: What is the difference between peak wavelength and dominant wavelength?
A2: Peak wavelength (λ_P) is the wavelength at which the emission spectrum has its highest intensity. Dominant wavelength (λ_d) is the single wavelength of monochromatic light that matches the perceived color of the LED when compared to a reference white light. λ_d is more relevant for color specification.

Q3: Why is the storage condition for an opened package stricter than for a sealed one?
A3: The sealed package contains desiccant to maintain a dry internal atmosphere. Once opened, the moisture-sensitive plastic package is exposed to ambient humidity, which it can absorb. Excessive absorbed moisture can vaporize rapidly during soldering (reflow), causing internal delamination or cracking (\"popcorning\").

Q4: How do I interpret the bin code on the packing bag?
A4: The code indicates the performance bin for the LEDs in that bag. For example, a code might specify \"Q-K-S4\\