LTW-108SEG-W White LED Datasheet - SMD Package - 3.2V Typ - 120mW - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a high-brightness, white light-emitting diode (LED) in a standard surface-mount device (SMD) package. The component is designed for automated assembly processes and is compliant with lead-free (Pb-free) and RoHS environmental standards, qualifying it as a green product. Its primary application is in general electronic equipment requiring reliable, compact indicator lighting or backlighting.

2. Key Features and Specifications

The LED is packaged on 12mm tape wound onto 7-inch diameter reels, making it fully compatible with high-speed automatic pick-and-place equipment used in modern electronics manufacturing. It is designed to withstand standard infrared (IR) and vapor phase reflow soldering processes. The package conforms to EIA (Electronic Industries Alliance) standards and features integrated circuit (I.C.) compatible drive characteristics.

The specific model features a yellow-tinted lens and utilizes an Indium Gallium Nitride (InGaN) semiconductor material to produce white light. The device is classified as Moisture Sensitivity Level (MSL) 3 per JEDEC standard J-STD-020, which dictates specific handling and storage requirements prior to soldering to prevent moisture-induced damage.

3. Absolute Maximum Ratings

Operating or storing the device beyond these limits may cause permanent damage.

• Power Dissipation (Pd): 120 mW
• Peak Forward Current (I_F(peak)): 100 mA (at 1/10 duty cycle, 0.1ms pulse width)
• DC Forward Current (I_F): 30 mA
• Reverse Voltage (V_R): 5 V
• Operating Temperature Range (T_opr): -30°C to +85°C
• Storage Temperature Range (T_stg): -40°C to +100°C
• Reflow Soldering Condition: 260°C peak temperature for a maximum of 10 seconds (lead-free process).

Critical Note: Applying a reverse bias voltage to the LED in an application circuit can result in immediate component failure or degradation.

4. Electrical & Optical Characteristics

All parameters are specified at an ambient temperature (T_a) of 25°C and a standard test current (I_F) of 20 mA, unless otherwise noted.

4.1 Luminous Intensity & Viewing Angle

The luminous intensity (I_V) is guaranteed to be between 1800 mcd (millicandela) and 2500 mcd, with a typical value provided. Intensity is measured using a sensor and filter combination that approximates the photopic (CIE) human eye response curve. The device features a wide viewing angle (2θ_1/2) of 110 degrees, defined as the full angle at which the luminous intensity drops to half of its peak axial value.

4.2 Chromaticity & Forward Voltage

The white light color is defined by its chromaticity coordinates on the CIE 1931 (x, y) diagram. The typical coordinates are x=0.295 and y=0.285. A tolerance of ±0.01 is applied to these coordinates in the product guarantee. The forward voltage (V_F) typically measures 3.2V but can range from 2.9V to 3.6V when driven at 20 mA. This variation is managed through a binning system.

4.3 Test Standards and Handling Precautions

The chromaticity and luminous intensity are tested according to the CAS140B standard. The datasheet strongly emphasizes Electrostatic Discharge (ESD) sensitivity. Static electricity or power surges can irreparably damage the LED. It is recommended to use a grounded wrist strap or anti-static gloves during handling, and to ensure all workstations, tools, and equipment are properly grounded.

5. Binning System Explanation

To ensure consistency in applications, the LEDs are sorted into bins based on key electrical and optical parameters. This allows designers to select components with tightly controlled characteristics.

5.1 Forward Voltage (V_F) Binning

LEDs are categorized into bins (V0 through V6) based on their forward voltage at 20 mA. Each bin covers a 0.1V range, from a minimum of 2.9V (V0) to a maximum of 3.6V (V6). A tolerance of ±0.10V is applied within each bin.

5.2 Luminous Intensity (I_V) Binning

LEDs are also binned for luminous intensity (S9 through S15). Each bin represents a 100 mcd range, starting from 1800-1900 mcd (S9) up to 2400-2500 mcd (S15). A tolerance of ±10% is applicable to the intensity within each designated bin.

6. Performance Curve Analysis

The datasheet references typical performance curves which illustrate the relationship between various parameters. 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 non-linear fashion, eventually saturating.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the decrease in light output as the junction temperature of the LED rises.
• Forward Voltage vs. Forward Current: Depicts the diode's I-V characteristic curve.
• Viewing Angle Pattern: A polar plot showing the spatial distribution of light intensity.

These curves are essential for understanding the device's behavior under different operating conditions and for effective thermal and electrical design.

7. Mechanical & Package Information

The LED comes in a standard SMD package. Detailed dimensioned drawings are provided for the component itself, the carrier tape used for automated handling, and the 7-inch reel. All dimensions are specified in millimeters, with a standard tolerance of ±0.1mm unless otherwise stated. The tape and reel packaging conforms to EIA-481-1-B specifications.

7.1 Packaging Specifications

• Reel Size: 7-inch diameter.
• Quantity per Reel: 2000 pieces.
• Minimum Order Quantity (MOQ) for Remainders: 500 pieces.
• Tape: Components are housed in 12mm wide embossed carrier tape sealed with a top cover tape.

8. Soldering & Assembly Guidelines

8.1 Reflow Soldering

The component is qualified for lead-free reflow soldering with a peak temperature of 260°C for up to 10 seconds. A recommended reflow profile according to J-STD-020D is referenced, which includes a pre-heat stage. The datasheet also provides recommended pad layout dimensions on the printed circuit board (PCB) to ensure reliable solder joint formation during infrared or vapor phase reflow.

8.2 Hand Soldering

If hand soldering is necessary, a soldering iron with a tip temperature not exceeding 300°C should be used, with the solder contact time limited to a maximum of 3 seconds per joint. This should be performed only once to prevent thermal damage to the package.

8.3 Cleaning

If post-solder cleaning is required, only specified solvents should be used. The LED can be immersed in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute. The use of unspecified chemical cleaners is prohibited as they may damage the LED package material.

9. Storage & Handling

Due to its MSL 3 rating, strict moisture control is required:

• Sealed Bag: Store at ≤30°C and ≤90% Relative Humidity (RH). Shelf life is one year from the date code when stored in the original moisture-barrier bag with desiccant.
• Opened Bag: After opening, store at ≤30°C and ≤60% RH. The components must be soldered within 168 hours (7 days) of exposure to the factory floor environment. If the humidity indicator card turns pink (indicating >10% RH) or the 168-hour window is exceeded, the LEDs must be baked at 60°C for at least 48 hours before use. Any remaining components should be resealed with desiccant.

10. Application Design Notes

10.1 Drive Circuit Design

An LED is a current-driven device. To ensure uniform brightness when driving multiple LEDs in parallel, it is strongly recommended to use a individual current-limiting resistor in series with each LED. The alternative method of connecting multiple LEDs directly in parallel with a single shared resistor (Circuit B in the datasheet) is discouraged. Variations in the forward voltage (V_F) characteristic from one LED to another will cause an uneven current distribution in a parallel configuration without individual resistors, leading to significant differences in brightness and potential over-current failure of the LED with the lowest V_F.

10.2 Application Scope & Reliability Disclaimer

The LED is intended for use in ordinary electronic equipment such as office automation devices, communication equipment, and household appliances. For applications requiring exceptional reliability where failure could risk life or health—such as in aviation, transportation, medical life-support systems, or safety devices—specific consultation and qualification with the manufacturer is required prior to design-in.

10.3 ESD Protection in Application

The ESD sensitivity noted during handling also extends to the application circuit. Designers should consider implementing protection measures on the PCB, such as transient voltage suppression (TVS) diodes or resistors, if the LED connections are exposed to potential static discharge or voltage surges in the end-use environment.

11. Technical Comparison & Design Considerations

Compared to older through-hole LED technologies, this SMD component offers significant advantages in manufacturing speed, board space savings, and reliability by eliminating manual insertion and wave soldering. The wide 110-degree viewing angle makes it suitable for applications requiring broad illumination or visibility from multiple angles, as opposed to narrow-angle LEDs used for focused beams. The InGaN technology for white light typically offers good efficiency and longevity. Key design considerations include managing the forward current to stay within the absolute maximum ratings, accounting for the forward voltage bin when designing the drive circuitry, and implementing proper thermal management on the PCB to keep the junction temperature low, thereby maintaining light output and long-term reliability.

12. Frequently Asked Questions (FAQ)

Q: Can I drive this LED directly from a 5V or 3.3V logic supply?
A: No. You must use a series current-limiting resistor. For example, with a 3.3V supply and a typical V_F of 3.2V at 20mA, a resistor of (3.3V - 3.2V) / 0.02A = 5 Ohms would be required. Always calculate for the minimum V_F in your selected bin to ensure the current does not exceed the maximum rating.

Q: Why is the luminous intensity given as a range (1800-2500 mcd)?
A: This is the total production spread. For consistent brightness in your product, you should specify and purchase LEDs from a single intensity bin (e.g., S12: 2100-2200 mcd).

Q: What does "MSL 3" mean for my production process?
A: It means the components can be exposed to the factory environment for up to 168 hours (7 days) after the sealed bag is opened before they must be soldered. If this time is exceeded, they require a baking process to remove absorbed moisture that could cause "popcorning" (package cracking) during reflow soldering.

Q: Is a heat sink necessary?
A> For continuous operation at the maximum DC current (30mA) or in high ambient temperatures, careful thermal design is necessary. While a dedicated heat sink may not be needed for low-duty-cycle indicator use, ensuring the LED's thermal pad has a good connection to a copper pour on the PCB will help dissipate heat and maintain performance.

13. Practical Application Example

Scenario: Designing a status indicator panel with 10 uniformly bright white LEDs.

1. Circuit Design: Use a constant current LED driver IC or a voltage regulator with individual series resistors for each LED. Assuming a 5V supply and targeting 20mA per LED, select LEDs from the V3 bin (V_F = 3.2-3.3V). The resistor value would be R = (5V - 3.25V_max) / 0.02A ≈ 87.5 Ohms. Use a standard 91 Ohm or 100 Ohm resistor, and recalculate the actual current.
2. Component Selection: Specify all 10 LEDs from the same luminous intensity bin (e.g., S12) and the same forward voltage bin (e.g., V3) to ensure visual consistency.
3. PCB Layout: Follow the recommended pad dimensions from the datasheet. Connect the thermal pad (if present) to a grounded copper area to aid heat dissipation.
4. Manufacturing: Program the pick-and-place machine for the 12mm tape feeder. Use the referenced lead-free reflow profile with a 260°C peak.
5. Handling: Keep the reel in its sealed bag until ready for production. Once opened, complete the assembly of all 10 boards within the 168-hour floor life.

14. Operating Principle & Technology

This LED generates white light using an InGaN (Indium Gallium Nitride) semiconductor chip that emits light in the blue region of the spectrum. This blue light is then partially converted to longer wavelengths (yellow, red) by a phosphor coating inside the package. The combination of the remaining blue light and the phosphor-converted light mixes to produce the perception of white light. This method is known as phosphor-converted white LED technology and is common for achieving high efficiency and good color rendering. The wide viewing angle is a result of the package lens design, which diffuses and spreads the light emitted from the chip and phosphor.

15. Industry Trends

The component reflects several ongoing trends in optoelectronics: the continued dominance of surface-mount technology for miniaturization and automated assembly; the widespread adoption of lead-free and RoHS-compliant manufacturing processes; and the use of advanced semiconductor materials like InGaN for efficient solid-state lighting. Furthermore, the detailed binning structure highlights the industry's focus on providing consistent and predictable performance for high-volume, quality-sensitive applications. The emphasis on MSL handling and standardized reflow profiles underscores the integration of discrete components into highly automated, streamlined global electronics supply chains.