LTW-S225DSKF-F SMD LED Datasheet - Side Looking Dual Color (White/Orange) - 20mA - 74mW/48mW - English Technical Document

1. Product Overview

The LTW-S225DSKF-F is a compact, side-looking, dual-color Surface Mount Device (SMD) LED lamp. It is engineered for automated printed circuit board (PCB) assembly, making it ideal for space-constrained applications in modern electronic devices. The package features a yellow lens and houses two distinct LED chips: one emitting white light (InGaN-based) and the other emitting orange light (AlInGaP-based). This configuration allows for versatile indication and backlighting functions within a single, miniature footprint.

1.1 Core Advantages

• Dual-Color Functionality: Integrates white and orange light sources in one package, saving board space and simplifying design.
• High Brightness: Utilizes ultra-bright AlInGaP and InGaN semiconductor technology for excellent luminous intensity.
• Manufacturing Compatibility: Designed for compatibility with automatic placement equipment and infrared (IR) reflow soldering processes, facilitating high-volume production.
• Standardized Packaging: Supplied on 8mm tape wound on 7-inch reels, conforming to EIA standards for efficient handling.
• Environmental Compliance: The product meets RoHS (Restriction of Hazardous Substances) directives.

1.2 Target Markets and Applications

This component is suitable for a broad spectrum of electronic equipment where reliable, compact indicators are required. Primary application areas include:

• Telecommunication Devices: Status indicators in cordless phones, cellular phones, and network equipment.
• Portable Computing: Keyboard or keypad backlighting in notebook computers and other mobile devices.
• Consumer & Industrial Electronics: Indicator lights in home appliances, office automation equipment, and industrial control panels.
• Display Technology: Suitable for micro-displays and symbolic luminaires requiring clear, colored indication.

2. Technical Parameters: In-Depth Objective Interpretation

This section provides a detailed analysis of the LED's operational limits and performance characteristics under standard test conditions (Ta=25°C).

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.

Parameter	White Chip	Orange Chip	Unit
Power Dissipation (Pd)	74	48	mW
Peak Forward Current (1/10 Duty, 0.1ms Pulse)	100	40	mA
Continuous DC Forward Current (IF)	20	20	mA
Reverse Voltage (VR)	5	5	V
Operating Temperature Range	-20°C to +80°C		°C
Storage Temperature Range	-30°C to +85°C		°C

Interpretation: The white chip has a higher permissible power dissipation (74mW vs. 48mW), indicating potentially different thermal characteristics or chip efficiency. Both chips share the same maximum continuous current of 20mA, which is the standard drive current for testing and typical operation. The 5V reverse voltage rating is relatively low, emphasizing the need for proper circuit design to avoid accidental reverse bias, which is only intended for infrared testing.

2.2 Electro-Optical Characteristics

Measured at the standard test condition of IF = 20mA and Ta = 25°C.

Parameter	Symbol	White (Min/Typ/Max)	Orange (Min/Typ/Max)	Unit	Condition/Note
Luminous Intensity	Iv	112 / - / 450	45 / - / 180	mcd	Note 1,2,5
Viewing Angle (2θ1/2)	-	130 (Typical)		deg	Fig.5
Peak Wavelength	λP	-	611 (Typical)	nm	-
Dominant Wavelength	λd	-	605 (Typical)	nm	Note 3,5
Forward Voltage	VF	2.5 / - / 3.7	1.7 / - / 2.4	V	IF=20mA

Interpretation:

• Brightness & Binning: The wide Iv range (e.g., 112-450 mcd for white) necessitates a binning system to ensure consistency in production batches. The orange chip's typical dominant wavelength of 605nm and peak at 611nm confirms its color in the orange/amber spectrum.
• Viewing Angle: A 130-degree viewing angle classifies this as a wide-angle LED, suitable for applications where visibility from off-axis positions is important.
• Forward Voltage: The orange AlInGaP chip exhibits a lower typical forward voltage (VF ~1.7-2.4V) compared to the white InGaN chip (VF ~2.5-3.7V). This is a critical parameter for driver circuit design, as power supply requirements differ between the two colors.

2.3 Thermal Characteristics & Soldering

The device is rated for infrared reflow soldering with a peak temperature of 260°C for a maximum of 10 seconds. This is compatible with standard lead-free (Pb-free) solder process profiles. The operating and storage temperature ranges are standard for commercial-grade SMD LEDs.

3. Binning System Explanation

To manage natural variations in semiconductor manufacturing, LEDs are sorted into performance bins. The LTW-S225DSKF-F uses two primary binning criteria.

3.1 Luminous Intensity (Iv) Binning

LEDs are sorted based on their measured luminous intensity at 20mA.

White Chip Bins:

• R Bin: 112.0 mcd (Min) to 180.0 mcd (Max)
• S Bin: 180.0 mcd to 280.0 mcd
• T Bin: 280.0 mcd to 450.0 mcd

Tolerance within each bin is ±15%.

Orange Chip Bins:

• P Bin: 45.0 mcd to 71.0 mcd
• Q Bin: 71.0 mcd to 112.0 mcd
• R Bin: 112.0 mcd to 180.0 mcd

Tolerance within each bin is ±15%.

3.2 Hue (Color Coordinate) Binning

For the white LED, color consistency is ensured by binning based on CIE 1931 chromaticity coordinates (x, y). The datasheet defines several bins (e.g., S1-1, S1-2, S2-1, etc.), each specifying a small quadrilateral area on the color chart. The tolerance for the (x, y) coordinates within any given hue bin is ±0.01. This tight control is essential for applications requiring uniform white color appearance across multiple LEDs.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Fig.5 for viewing angle), typical relationships can be described based on LED physics:

• Current vs. Luminous Intensity (I-Iv Curve): Luminous intensity generally increases with forward current in a sub-linear fashion. Driving the LED above 20mA may yield higher light output but will increase power dissipation and junction temperature, potentially affecting longevity and color shift.
• Forward Voltage vs. Current (V-I Curve): The V-I characteristic is exponential, typical of a diode. The forward voltage (VF) increases with current and decreases with rising junction temperature.
• Temperature Dependence: The luminous intensity of LEDs typically decreases as junction temperature increases. The AlInGaP (orange) chip may exhibit less thermal quenching than the InGaN (white) chip at higher temperatures, but both will see reduced output. Forward voltage also has a negative temperature coefficient.

5. Mechanical and Package Information

5.1 Package Dimensions and Pin Assignment

The SMD package has a specific footprint. Critical dimensions include length, width, and height, all with a standard tolerance of ±0.1mm unless otherwise noted. The pin assignment is crucial for correct circuit connection:

• Pins 1 & 2: Anode and Cathode for the Orange AlInGaP LED chip.
• Pins 3 & 4: Anode and Cathode for the White InGaN LED chip.

Proper polarity must be observed during assembly.

5.2 Recommended PCB Pad Design and Soldering Orientation

The datasheet includes a suggested land pattern (copper pad layout) for the PCB. Following this recommendation ensures reliable solder joint formation, proper mechanical stability, and correct alignment during reflow. The diagram also indicates the recommended orientation of the LED on the tape relative to the soldering direction to minimize tombstoning or misalignment.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Parameters

For lead-free solder processes, the following condition is suggested:

• Peak Temperature: 260°C maximum.
• Time at Peak: 10 seconds maximum.
• Pre-heat: 150°C to 200°C.
• Pre-heat Time: 120 seconds maximum.

The LED can withstand this reflow profile a maximum of two times.

6.2 Hand Soldering (If Required)

If manual soldering is necessary:

• Iron Temperature: 300°C maximum.
• Soldering Time: 3 seconds maximum per lead.
• Important: Hand soldering should be performed only once.

6.3 Cleaning

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

6.4 Storage and Handling

• ESD Precautions: LEDs are sensitive to electrostatic discharge (ESD). Proper ESD controls (wrist straps, grounded equipment) must be used during handling.
• Moisture Sensitivity: As per standard MSL (Moisture Sensitivity Level) precautions for SMD packages:\li>
• Sealed Bag: LEDs in the original moisture-proof bag with desiccant should be stored at ≤30°C and ≤90% RH. The "floor life" after bag opening is one week for IR reflow.
• Exposed Devices: If stored outside the original packaging for over a week, a bake-out at 60°C for at least 20 hours is recommended before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied in embossed carrier tape for automated assembly:

• Tape Width: 8 mm.
• Reel Diameter: 7 inches (178 mm).
• Quantity per Reel: 4000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Packaging Standard: Conforms to ANSI/EIA-481 specifications.

The tape is sealed with a cover tape to protect components. The maximum allowed number of consecutive missing components in the tape is two.

8. Application Suggestions and Design Considerations

8.1 Typical Application Circuits

Each LED chip (white and orange) requires its own current-limiting resistor when driven from a voltage source (e.g., 3.3V or 5V rail). The resistor value (R) can be calculated using Ohm's Law: R = (V_supply - VF_LED) / I_LED. Example: For the white LED with VF = 3.2V (typical), driven at 20mA from a 5V supply: R = (5V - 3.2V) / 0.02A = 90 Ohms. A standard 91-ohm resistor would be suitable. This calculation must be performed separately for each color due to their different VF values.

8.2 Design Considerations

• Thermal Management: Although power dissipation is low, ensuring adequate PCB copper area around the pads helps dissipate heat, maintaining LED performance and longevity, especially in high ambient temperature environments.
• Current Driving: Constant current driving is preferable to constant voltage for maintaining consistent brightness and color, as VF varies with temperature and between individual units.
• Optical Design: The side-looking emission profile is ideal for edge-lighting light guides or for indication where the LED is mounted perpendicular to the viewing surface. Consider the 130-degree viewing angle when designing light pipes or apertures.

9. Technical Comparison and Differentiation

The primary differentiating factors of the LTW-S225DSKF-F are:

1. Dual-Chip, Side-Looking Configuration: This is a specialized package not found in standard top-emitting LEDs. It allows two independent indicator colors from a single device mounted on the edge of a PCB.
2. Chip Technology Combination: The use of AlInGaP for orange and InGaN for white represents an optimized choice for efficiency and color quality in their respective spectra.
3. Manufacturing Readiness: Full compatibility with automated SMT processes (placement, IR reflow) and standard tape-and-reel packaging makes it a production-friendly component.

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive the white and orange LEDs simultaneously at 20mA each?
A1: Electrically, yes, as they have independent anodes and cathodes. However, you must consider the total power dissipation on the small package. Simultaneous operation at full current generates more heat, which could affect performance and reliability. Derating the current or implementing thermal management is advised for continuous dual-operation.

Q2: Why is the reverse voltage rating only 5V?
A2: LEDs are not designed to operate in reverse bias. The 5V rating is a withstand voltage for testing and protection against accidental reverse connection. In circuit design, ensure the LED is never exposed to a reverse voltage exceeding this limit, typically by placing it in series with a diode that only allows forward current.

Q3: What do the bin codes (R, S, T, P, Q) mean when ordering?
A3: These codes specify the guaranteed minimum luminous intensity of the LEDs in a batch. For example, ordering "White, T bin" guarantees each LED will have an intensity between 280 and 450 mcd at 20mA. Specifying the bin ensures brightness consistency across your production run. The hue bin (e.g., S2-1) should also be specified for the white LEDs if color uniformity is critical.

11. Practical Use Case Example

Scenario: Status Indicator for a Network Router
A designer needs dual-status indication (e.g., "Power On" and "Network Activity") on the front panel of a compact router. Space is limited.
Implementation: A single LTW-S225DSKF-F LED is mounted vertically on the main PCB, positioned at the edge facing a light guide that channels light to the front panel. The orange chip is connected to the "Power" circuit and glows steadily when powered. The white chip is connected to the network processor and is programmed to blink upon detecting data activity. This solution saves PCB area, reduces part count, and uses a single light guide for two distinct visual signals.

12. Operating Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light through electroluminescence. When a forward voltage is applied across the p-n junction, electrons and holes recombine, releasing energy in the form of photons. The color of the light is determined by the energy bandgap of the semiconductor material.

• InGaN (Indium Gallium Nitride): This material system is used for the white LED. Typically, a blue-emitting InGaN chip is coated with a phosphor layer. The blue light excites the phosphor, which then re-emits a broad spectrum of light, combining with the remaining blue light to produce white.
• AlInGaP (Aluminum Indium Gallium Phosphide): This material is used for the orange LED. It is a direct bandgap semiconductor well-suited for producing high-efficiency light in the red, orange, amber, and yellow wavelengths.

The side-looking package incorporates these two distinct semiconductor chips within a single molded plastic housing with a shared yellow-tinted lens.

13. Technology Trends

The development of SMD LEDs like the LTW-S225DSKF-F follows several key industry trends:

1. Miniaturization & Integration: The drive towards smaller, more integrated components continues. Multi-chip packages (like this dual-color LED) save space and simplify assembly compared to using two separate discrete LEDs.
2. Increased Efficiency & Brightness: Ongoing improvements in epitaxial growth and chip design yield higher luminous efficacy (more light output per electrical watt) for both InGaN and AlInGaP technologies.
3. Enhanced Reliability & Robustness: Advancements in packaging materials, phosphor technology, and thermal management contribute to longer operational lifetimes and better performance under harsh conditions.
4. Standardization for Automation: Components are increasingly designed from the ground up for compatibility with high-speed, precision SMT assembly lines, including standardized packaging (tape & reel) and reflow profiles.

These trends ensure that SMD LEDs remain fundamental, high-performance components for indication and illumination across the electronics industry.