Dual Color SMD LED LTW-C235DSKF-5A Datasheet - White & Orange - 20-30mA - 72-75mW - English Technical Document

1. Product Overview

This document details the specifications for a high-performance, dual-color Surface Mount Device (SMD) LED. The component integrates two distinct LED chips within a single package: one emitting white light and the other emitting orange light. This design is engineered for applications requiring multiple indicator states or color-coded signaling from a compact footprint.

The LED is constructed using advanced semiconductor materials. The white light is generated by an InGaN (Indium Gallium Nitride) based chip, while the orange light originates from an AlInGaP (Aluminium Indium Gallium Phosphide) based chip. This combination leverages the efficiency and brightness characteristics of both material systems.

Key advantages of this product include its compliance with RoHS (Restriction of Hazardous Substances) directives, designation as a Green Product, and compatibility with standard high-volume manufacturing processes. It is supplied on tape and reel packaging suitable for automated pick-and-place equipment and is rated for infrared (IR) reflow soldering processes, making it ideal for modern PCB assembly lines.

2. Technical Specifications Deep Dive

2.1 Absolute Maximum Ratings

Operating the device beyond these limits may cause permanent damage. Ratings are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation: White: 72 mW, Orange: 75 mW. This parameter defines the maximum power the LED can dissipate as heat under continuous operation.
• Peak Forward Current: White: 100 mA, Orange: 80 mA. This is the maximum allowable pulsed current (1/10 duty cycle, 0.1ms pulse width) for brief, high-intensity flashes.
• DC Forward Current: White: 20 mA, Orange: 30 mA. This is the recommended maximum continuous forward current for reliable long-term operation.
• Reverse Voltage: 5 V for both colors. Applying a voltage exceeding this value in the reverse direction can damage the LED junction. Continuous reverse voltage operation is prohibited.
• Temperature Ranges: Operating: -20°C to +80°C; Storage: -30°C to +100°C. These define the environmental limits for functionality and non-operational storage.
• Infrared Soldering Condition: Withstands 260°C for 10 seconds, defining its compatibility with standard lead-free reflow profiles.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at Ta=25°C and a test current (IF) of 5mA, unless otherwise stated.

• Luminous Intensity (Iv): A measure of perceived light output. White: Min. 45.0 mcd, Typ. (not specified), Max. 180.0 mcd. Orange: Min. 11.2 mcd, Typ. (not specified), Max. 71.0 mcd. Intensity is measured using a sensor filtered to match the human eye's photopic response (CIE curve).
• Viewing Angle (2θ1/2): Approximately 130 degrees for both colors. This is the angle at which the luminous intensity drops to half of its peak value, defining the beam spread.
• Forward Voltage (VF): The voltage drop across the LED when conducting. White: Typ. 2.85V, Max. 3.15V. Orange: Typ. 2.00V, Max. 2.40V. This is crucial for circuit design and current-limiting resistor calculation.
• Peak Emission Wavelength (λP): For the orange LED, the typ. value is 611 nm, which is the wavelength at which the spectral power distribution is highest.
• Dominant Wavelength (λd): For the orange LED, the typ. value is 605 nm. This is the single wavelength perceived by the human eye to represent the color, derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): For the orange LED, typ. 20 nm. This indicates the spectral purity or bandwidth of the emitted light.
• Chromaticity Coordinates (x, y): For the white LED, typ. (0.3, 0.3) on the CIE 1931 diagram. A tolerance of ±0.01 applies. These coordinates precisely define the color point of the white light.
• Reverse Current (IR): Max. 10 μA at VR=5V for both colors, indicating the very small leakage current when the device is reverse-biased within its limits.

Electrostatic Discharge (ESD) Caution: LEDs are sensitive to static electricity. Proper ESD precautions, such as using grounded wrist straps, anti-static mats, and equipment, are mandatory during handling to prevent latent or catastrophic damage.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins. The specific bin code for a given lot is marked on its packaging.

3.1 Forward Voltage (VF) Binning for White LED

LEDs are categorized based on their forward voltage at IF=5mA. Each bin has a tolerance of ±0.1V.

- Bin A: 2.55V - 2.70V

- Bin B: 2.70V - 2.85V

- Bin C: 2.85V - 3.00V

- Bin D: 3.00V - 3.15V

3.2 Luminous Intensity (Iv) Binning

White LED (at IF=5mA, tolerance ±15% per bin):

- Bin P: 45.0 mcd - 71.0 mcd

- Bin Q: 71.0 mcd - 112.0 mcd

- Bin R: 112.0 mcd - 180.0 mcd

Orange LED (at IF=5mA):

- Bin L: 11.2 mcd - 18.0 mcd

- Bin M: 18.0 mcd - 28.0 mcd

- Bin N: 28.0 mcd - 45.0 mcd

- Bin P: 45.0 mcd - 71.0 mcd

3.3 Hue (Color) Binning for White LED

The white light's color point is binned according to its chromaticity coordinates (x, y) on the CIE 1931 diagram at IF=5mA. Six bins (S1 through S6) are defined by specific quadrilateral regions on the chromaticity chart. A tolerance of ±0.01 applies to the (x, y) coordinates within each bin. This ensures visual color consistency between different production batches.

4. Performance Curve Analysis

The datasheet references typical characteristic curves which graphically represent device behavior. While the specific graphs are not reproduced in text, they typically include:

• Relative Luminous Intensity vs. Forward Current: Shows how light output increases with current, usually in a sub-linear relationship, highlighting efficiency changes.
• Forward Voltage vs. Forward Current: Demonstrates the diode's I-V characteristic, crucial for thermal management and driver design.
• Relative Luminous Intensity vs. Ambient Temperature: Illustrates the decrease in light output as junction temperature rises, a key factor for thermal design.
• Spectral Power Distribution: For the orange LED, this curve would show the intensity of light emitted at each wavelength, centered around 611 nm with a 20 nm half-width.

These curves are essential for designers to predict performance under non-standard conditions (different currents, temperatures) and to optimize the application circuit.

5. Mechanical & Package Information

5.1 Part Number and Pin Assignment

Part Number: LTW-C235DSKF-5A

Lens Color: Yellow (affects light diffusion and appearance when off).

Emitted Colors & Pin Assignment:

- InGaN White Chip: Connected to pins 1 and 2.

- AlInGaP Orange Chip: Connected to pins 3 and 4.

This 4-pin configuration allows independent control of the two colors.

5.2 Package Dimensions

The LED conforms to an EIA (Electronic Industries Alliance) standard SMD package outline. All dimensions are in millimeters with a standard tolerance of ±0.10 mm unless otherwise specified. The datasheet includes a detailed dimensional drawing showing the package's length, width, height, lead spacing, and other critical mechanical features necessary for PCB land pattern design.

5.3 Suggested Soldering Pad Dimensions

A recommended PCB land pattern (pad layout) is provided to ensure reliable solder joint formation during reflow soldering. Adhering to these dimensions promotes proper solder fillet formation, mechanical stability, and thermal relief.

6. Soldering, Assembly & Handling Guidelines

6.1 Soldering Process

The device is fully compatible with infrared (IR) reflow soldering processes. A suggested reflow profile is provided, with a peak temperature condition of 260°C for 10 seconds, aligning with common lead-free solder requirements. Following the recommended profile is critical to prevent thermal damage to the LED package or die.

6.2 Cleaning

If post-solder cleaning is necessary, only specified chemicals should be used. Unspecified solvents may damage the epoxy lens or package. The recommended method is immersion in ethyl alcohol or isopropyl alcohol at normal room temperature for a duration of less than one minute.

6.3 Storage Conditions

Sealed Package (with desiccant): Store at ≤30°C and ≤90% Relative Humidity (RH). The shelf life under these conditions is one year.

Opened Package: Components must be stored at ≤30°C and ≤60% RH. It is strongly recommended to complete the IR reflow process within one week of opening the moisture-proof bag.

Extended Storage (Opened): For storage beyond one week, place components in a sealed container with desiccant or in a nitrogen desiccator.

Rebaking: LEDs stored out of their original packaging for more than one week require a bake at approximately 60°C for at least 20 hours prior to soldering to remove absorbed moisture and prevent \"popcorning\" (package cracking) during reflow.

7. Packaging & Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied in embossed carrier tape with a protective cover tape, wound onto 7-inch (approximately 178 mm) diameter reels. This packaging is compliant with ANSI/EIA 481-1-A-1994 standards.

• Pieces per Reel: 3000 units.
• Minimum Order Quantity (MOQ) for Remainders: 500 pieces.
• Cover Tape: Empty pockets in the carrier tape are sealed with the cover tape.
• Missing Lamps: The maximum allowable number of consecutive missing components on a reel is two.

Detailed dimensional drawings for the carrier tape (pocket size, pitch, etc.) and the reel (hub diameter, flange diameter, etc.) are provided in the datasheet for compatibility with automated assembly equipment.

8. Application Notes & Design Considerations

8.1 Intended Use

This LED is designed for use in standard electronic equipment, including office automation devices, communication equipment, and household appliances. For applications demanding exceptional reliability where failure could risk life or health (e.g., aviation, medical systems, safety devices), specific consultation and qualification are required prior to design-in.

8.2 Circuit Design

• Current Limiting: An external current-limiting resistor is mandatory for each LED color. The resistor value (R) can be calculated using Ohm's Law: R = (Vsupply - VF) / IF, where VF is the forward voltage of the specific color/batch and IF is the desired operating current (not to exceed the DC Forward Current rating).
• Thermal Management: While power dissipation is low, ensuring adequate PCB copper area or thermal vias can help maintain a lower junction temperature, preserving luminous output and longevity.
• Parallel/Series Connection: Connecting LEDs directly in parallel is generally not recommended due to VF variations, which can cause current imbalance. Series connection with a common current-limiting resistor is preferred for uniform brightness.

8.3 Typical Application Scenarios

• Status Indicators: Dual-color capability allows for multiple states (e.g., White=On, Orange=Standby, Both=Warning).
• Backlighting for Keypads or Icons: Selective backlighting in different colors.
• Consumer Electronics: Power, connectivity, or mode indicators in devices like routers, chargers, or audio equipment.
• Automotive Interior Indicators: (If qualified for the specific application environment).

9. Technical Comparison & Differentiation

This dual-color LED offers distinct advantages in specific applications:

• vs. Two Single-Color LEDs: Saves PCB space, reduces placement time/cost (one component vs. two), and ensures precise mechanical alignment of the two light sources.
• Material Technology: Uses optimized chip materials (InGaN for white, AlInGaP for orange) for high efficiency and brightness in their respective spectra, rather than using a phosphor-converted orange which might be less efficient.
• Reverse Mount Design: The mention of \"reverse mount\" suggests a package design where the primary light emission is through the substrate or in a specific direction, which may be advantageous for certain optical designs compared to standard top-emitting packages.

10. Frequently Asked Questions (FAQ)

Q1: Can I drive the white and orange LEDs simultaneously at their maximum DC current?

A1: Yes, but you must consider the total power dissipation on the package. Driving White at 20mA (~2.85V=57mW) and Orange at 30mA (~2.00V=60mW) gives a total of ~117mW, which exceeds the individual power ratings (72mW, 75mW). Simultaneous operation at full current may require derating or enhanced thermal management to keep the junction temperature within safe limits.

Q2: What is the difference between Peak Wavelength and Dominant Wavelength?

A2: Peak Wavelength (λP=611 nm) is the physical wavelength where the LED emits the most optical power. Dominant Wavelength (λd=605 nm) is a perceptual metric; it's the wavelength of monochromatic light that would appear to have the same color as the LED's output to a standard human observer. They often differ, especially for saturated colors.

Q3: Why is the storage humidity requirement stricter after the bag is opened?

A3: The sealed bag contains desiccant to maintain a very low humidity level, protecting the LEDs from moisture absorption. Once opened, the components are exposed to ambient humidity. Moisture absorbed into the plastic package can rapidly expand into steam during the high-temperature reflow soldering process, potentially causing internal delamination or cracking (\"popcorning\").

Q4: How do I interpret the bin codes for ordering?

A4: For consistent performance in your product, you should specify the required bins for VF, Iv, and Hue when ordering. For example, you might request \"LTW-C235DSKF-5A, VF Bin B, Iv Bin Q for White, Iv Bin M for Orange, Hue Bin S3\". This ensures all LEDs in your production run have closely matched electrical and optical properties.

11. Design-in Case Study Example

Scenario: Designing a status indicator for a network switch with three states: Off, Link Active (White), and Data Transmitting (Orange Flashing).

Implementation: A single LTW-C235DSKF-5A is used. The microcontroller (MCU) has two GPIO pins, each connected to one LED color via a current-limiting resistor.

Calculations: Using a 3.3V supply and targeting 10mA for good visibility while conserving power.

- For White (VF~2.85V): R = (3.3V - 2.85V) / 0.01A = 45 Ω. Use a standard 47 Ω resistor.

- For Orange (VF~2.00V): R = (3.3V - 2.00V) / 0.01A = 130 Ω. Use a standard 130 Ω or 120 Ω resistor.

PCB Layout: The recommended land pattern is used. A small keep-out area under the LED is maintained to prevent solder wicking. The MCU firmware controls the pins to achieve the desired steady and flashing states.

Result: A compact, reliable, and clear multi-state indicator using only one component footprint.

12. Operational Principles

LEDs are semiconductor diodes. When a forward voltage exceeding the chip's bandgap energy is applied, electrons and holes recombine in the active region, releasing energy in the form of photons (light). The color of the light is determined by the bandgap energy of the semiconductor material. InGaN materials have a wider bandgap, enabling emission in the blue/violet/ultraviolet range; white light is typically created by coating a blue InGaN chip with a yellow phosphor, mixing the light to appear white. AlInGaP materials have a bandgap suitable for direct emission in the red, orange, amber, and yellow parts of the spectrum, as used for the orange chip in this device. The dual-chip package electrically isolates the two semiconductor junctions, allowing them to be controlled independently.

13. Technology Trends

The optoelectronics industry continues to evolve. Trends relevant to components like this dual-color LED include:

Increased Efficiency: Ongoing improvements in internal quantum efficiency and light extraction techniques lead to higher luminous intensity (mcd) at the same or lower drive currents, improving system power efficiency.

Miniaturization: While this uses a standard package, there is a constant drive towards smaller package sizes (e.g., 0402, 0201 metric) for high-density electronics, though often at the expense of total light output or heat dissipation.

Color Consistency & Binning: Advances in epitaxial growth and manufacturing control are reducing the natural variation in VF and chromaticity, leading to tighter bin distributions and reducing the need for extensive binning or simplifying inventory management.

Integrated Solutions: A trend towards integrating the LED driver IC (constant current source, PWM controller) directly with the LED package or module, simplifying end-circuit design. This particular component remains a discrete, driver-less LED.

Reliability & Lifetime: Continuous improvements in packaging materials (epoxy, silicone) and die attach technologies enhance long-term reliability, lumen maintenance, and resistance to thermal and environmental stress.