LTW-C191TLA SMD LED Datasheet - 0.55mm Height - 3.4V Forward Voltage - White Color - 70mW Power - English Technical Document

1. Product Overview

The LTW-C191TLA is a surface-mount device (SMD) LED designed for modern electronic applications requiring compact form factors and high brightness. This product belongs to the category of ultra-thin chip LEDs, featuring a remarkably low profile of 0.55mm. It utilizes InGaN (Indium Gallium Nitride) technology to produce white light, offering a balance of performance and miniaturization suitable for space-constrained designs.

The core advantages of this LED include its compliance with RoHS (Restriction of Hazardous Substances) directives, making it an environmentally friendly "Green Product." Its super-thin profile allows for integration into increasingly slim consumer electronics, display backlighting, and indicator applications. The package is supplied on 8mm tape wound onto 7-inch diameter reels, ensuring compatibility with high-speed, automated pick-and-place assembly equipment commonly used in volume manufacturing. Furthermore, it is designed to withstand standard infrared (IR) reflow soldering processes, facilitating reliable PCB attachment.

The target market encompasses a wide range of industries, including consumer electronics (e.g., smartphones, tablets, wearables), automotive interior lighting, general signage, and control panel indicators where reliable, bright, and compact light sources are essential.

2. Technical Parameter Deep Dive

2.1 Absolute Maximum Ratings

Operating the device beyond these limits may cause permanent damage. Key ratings are specified at an ambient temperature (Ta) of 25\u00b0C.

• Power Dissipation (Pd): 70 mW. This is the maximum amount of power the LED can dissipate as heat without degradation.
• Peak Forward Current (I_F(PEAK)): 100 mA. This is the maximum allowable instantaneous current, typically under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). It is significantly higher than the continuous current rating.
• DC Forward Current (I_F): 20 mA. This is the recommended maximum continuous forward current for reliable long-term operation.
• Derating Factor: 0.25 mA/\u00b0C. For ambient temperatures above 25\u00b0C, the maximum allowable DC forward current must be reduced linearly by this factor to prevent overheating.
• Reverse Voltage (V_R): 5 V. Applying a reverse bias voltage exceeding this value can damage the LED junction.
• Operating Temperature Range: -20\u00b0C to +80\u00b0C. The ambient temperature range within which the LED is designed to function correctly.
• Storage Temperature Range: -40\u00b0C to +85\u00b0C. The temperature range for non-operational storage.
• Infrared Soldering Condition: 260\u00b0C for 10 seconds. The maximum recommended reflow profile peak temperature and time.

2.2 Electro-Optical Characteristics

These parameters define the LED's performance under typical operating conditions (Ta=25\u00b0C, I_F=10mA).

• Luminous Intensity (I_V): 112.0 - 300.0 mcd (millicandela). This is a measure of the perceived brightness of the LED as seen by the human eye. The wide range indicates a binning system is used (see Section 3). Measurement follows the CIE eye-response curve.
• Viewing Angle (2\u03b8_1/2): 130 degrees. This is the full angle at which the luminous intensity drops to half of its maximum value (on-axis). A 130-degree angle indicates a wide, diffuse light emission pattern.
• Chromaticity Coordinates (x, y): x=0.31, y=0.32. These coordinates on the CIE 1931 chromaticity diagram define the white point (color) of the emitted light. A tolerance of \u00b10.01 applies.
• Forward Voltage (V_F): 2.80 - 3.40 V. The voltage drop across the LED when driven at 10mA. This range is also subject to binning.
• Reverse Current (I_R): 10 \u03bcA (max). The small leakage current that flows when the maximum reverse voltage (5V) is applied.

Electrostatic Discharge (ESD) Caution: The LED is sensitive to static electricity and voltage surges. Proper ESD handling procedures, including the use of grounded wrist straps, anti-static mats, and equipment grounding, are mandatory during handling and assembly to prevent latent or catastrophic failures.

3. Binning System Explanation

To ensure consistent performance in production, LEDs are sorted into "bins" based on key parameters. The LTW-C191TLA uses a three-dimensional binning system.

3.1 Forward Voltage (V_F) Binning

LEDs are categorized by their forward voltage drop at 10mA. This helps in designing consistent current drive circuits, especially when multiple LEDs are used in series.

• Bin 2: V_F = 2.8V to 3.0V
• Bin 3: V_F = 3.0V to 3.2V
• Bin 4: V_F = 3.2V to 3.4V

Tolerance on each bin is \u00b10.1V.

3.2 Luminous Intensity (I_V) Binning

LEDs are sorted by their brightness output. The bin code is marked on the packaging.

• Bin R1: 112 mcd to 146 mcd
• Bin R2: 146 mcd to 180 mcd
• Bin S1: 180 mcd to 240 mcd
• Bin S2: 240 mcd to 300 mcd

Tolerance on each bin is \u00b115%.

3.3 Hue (Color) Binning

White LEDs can have slight variations in color temperature (warm white, cool white, etc.). This is defined by chromaticity coordinates (x, y) on the CIE 1931 diagram. The datasheet defines several hue bins (A0, B3, B4, B5, B6, C0) with specific coordinate boundaries. A graphical representation on the chromaticity diagram shows the areas covered by these bins. The tolerance for hue is \u00b10.01 in both x and y coordinates. This binning is crucial for applications requiring uniform color appearance across multiple LEDs.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Fig.6 for viewing angle, Fig.1 for chromaticity), typical performance trends can be inferred from the parameters.

• Current vs. Luminous Intensity (I-V Curve): For InGaN LEDs, luminous intensity generally increases with forward current but not linearly. Operating above the recommended DC current (20mA) may lead to increased efficiency droop, higher junction temperature, and reduced lifetime.
• Temperature Dependence: The luminous output and forward voltage of LEDs are temperature-sensitive. As junction temperature increases, luminous intensity typically decreases, and the forward voltage may slightly drop. The derating factor of 0.25 mA/\u00b0C is a direct measure to manage this thermal effect.
• Spectral Characteristics: As an InGaN-based white LED, it likely uses a blue-emitting chip combined with a phosphor coating to produce white light. The chromaticity coordinates (x=0.31, y=0.32) suggest a white point that is likely in the "cool white" or "neutral white" region.

5. Mechanical and Packaging Information

5.1 Package Dimensions

The LED features an EIA (Electronic Industries Alliance) standard package footprint. The key mechanical feature is its ultra-thin height of 0.55mm. Detailed dimensioned drawings are provided in the datasheet, with all units in millimeters (inches noted in parenthesis). A standard tolerance of \u00b10.10mm (.004") applies unless otherwise specified. These precise dimensions are critical for PCB layout and ensuring proper placement by automated machinery.

5.2 Pad Layout and Polarity

The datasheet includes a suggested soldering pad layout (land pattern) for PCB design. Adhering to this pattern ensures reliable solder joint formation and proper alignment during reflow. The LED package will have anode and cathode markings; correct polarity must be observed during assembly to ensure the device functions. The pad design also aids in heat dissipation from the LED die.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Parameters

The LED is compatible with infrared (IR) reflow processes. The maximum recommended condition is a peak temperature of 260\u00b0C for a duration not exceeding 10 seconds. A suggested profile includes a pre-heat stage at 150-200\u00b0C for up to 120 seconds maximum. It is critical to note that the LED should not be subjected to more than two reflow cycles under these conditions. For manual soldering with an iron, the tip temperature should not exceed 300\u00b0C, and contact time should be limited to 3 seconds, for one time only.

6.2 Storage and Handling

Moisture Sensitivity: The LEDs are packaged in a moisture-barrier bag with desiccant. While sealed, they should be stored at \u2264 30\u00b0C and \u2264 90% RH and used within one year. Once the bag is opened, the storage environment should be \u2264 30\u00b0C and \u2264 60% RH. Components exposed to ambient conditions for more than 672 hours (28 days) should be baked at approximately 60\u00b0C for at least 20 hours before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

6.3 Cleaning

If cleaning after soldering is necessary, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute is acceptable. Unspecified chemical cleaners may damage the LED package or lens.

7. Packaging and Ordering Information

The standard packaging format is 8mm embossed carrier tape on 7-inch (178mm) diameter reels. Each reel contains 5000 pieces of the LTW-C191TLA LED. For quantities less than a full reel, a minimum packing quantity of 500 pieces is available. The tape and reel specifications comply with ANSI/EIA 481-1-A-1994. The tape uses a top cover to seal empty pockets. The packaging hierarchy typically involves moisture barrier bags inside inner cartons, which are then packed into a master carton.

8. Application Recommendations

8.1 Typical Application Scenarios

• Backlighting: Ideal for edge-lit or direct-lit backlighting in ultra-thin displays, keypads, and control panels.
• Status Indicators: Power, connectivity, and status indicators in consumer electronics, networking equipment, and industrial controls.
• Decorative Lighting: Accent lighting in appliances, automotive interiors, and architectural features where a low profile is critical.
• General Illumination: Can be used in arrays for low-level ambient or task lighting.

8.2 Design Considerations

• Current Limiting: Always use a series resistor or constant-current driver to limit the forward current to 20mA DC or less. The circuit must account for the forward voltage bin of the LEDs used.
• Thermal Management: Despite its low power, ensure the PCB provides adequate thermal relief, especially if multiple LEDs are clustered or operated at high ambient temperatures. Follow the current derating guidelines.
• Optical Design: The 130-degree viewing angle provides wide dispersion. For focused light, secondary optics (lenses, light guides) will be required.
• ESD Protection: Incorporate ESD protection diodes on sensitive lines if the LED is in a user-accessible area, in addition to proper handling during assembly.

9. Technical Comparison and Differentiation

The primary differentiating factor of the LTW-C191TLA is its 0.55mm height. Compared to standard 0603 or 0402 package LEDs which are often 0.8-1.0mm tall, this represents a significant reduction in Z-height, enabling thinner end products. The combination of this ultra-thin profile with a relatively high luminous intensity (up to 300 mcd) is a key advantage. Furthermore, its compatibility with standard IR reflow and tape-and-reel packaging makes it as easy to assemble as thicker counterparts, without requiring special low-temperature processes that might compromise other components on the board.

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive this LED at 30mA for more brightness?
A: No. The Absolute Maximum Rating for DC forward current is 20mA. Exceeding this value increases junction temperature, accelerates lumen depreciation, and can lead to premature failure. For higher brightness, select an LED from a higher luminous intensity bin (e.g., S2) or use multiple LEDs.

Q2: What is the difference between Peak Forward Current and DC Forward Current?
A: DC Forward Current (20mA) is for continuous operation. Peak Forward Current (100mA) is a short-duration, pulsed rating (1/10 duty cycle, 0.1ms pulse width) used for multiplexing or brief signal flashes. The average current over time must still respect the power dissipation and thermal limits.

Q3: Why is binning important, and which bin should I specify?
A: Binning ensures color and brightness uniformity in your application. For a single indicator, any bin may suffice. For a multi-LED array (e.g., a backlight), you must specify the same V_F, I_V, and Hue bins to avoid visible differences in brightness or color between adjacent LEDs. Consult the bin code tables to select the appropriate performance window.

Q4: The datasheet mentions a 260\u00b0C reflow. Is this lead-free?
A: Yes, a peak temperature of 260\u00b0C is typical for lead-free (RoHS-compliant) solder reflow profiles. The LED's compatibility with this process confirms its suitability for modern lead-free assembly lines.

11. Practical Design and Usage Case

Case: Designing a Ultra-Thin Tablet Status Indicator Bar
A designer needs three white LEDs (power, wifi, battery) along the edge of a tablet bezel. The mechanical design allows only 0.6mm of space above the PCB. The LTW-C191TLA, with its 0.55mm height, is a perfect fit. The designer creates a PCB footprint matching the suggested pad layout. They specify Bin 3 for V_F (3.0-3.2V), Bin S1 for brightness (180-240 mcd), and Hue Bin B5 for a consistent neutral white color. A single current-limiting resistor is calculated for a 3.3V supply and a 15mA drive current (conservatively below the 20mA max) to ensure longevity and manage heat in the confined space. The LEDs are placed using automated equipment from the 8mm tape reel. The assembly undergoes a standard lead-free reflow profile with a 250\u00b0C peak, well within the device's rating. The result is a bright, uniform, and reliable indicator set that meets the stringent thickness requirement.

12. Technology Principle Introduction

The LTW-C191TLA is based on InGaN (Indium Gallium Nitride) semiconductor technology. InGaN LEDs are renowned for their ability to emit high-efficiency light in the blue and green regions of the spectrum. To produce white light, a common method is used: a blue InGaN LED chip is coated with a layer of yellow phosphor (often YAG:Ce). Some of the blue light from the chip is absorbed by the phosphor and re-emitted as yellow light. The combination of the remaining blue light and the converted yellow light appears white to the human eye. By adjusting the phosphor composition and thickness, different shades of white (correlated color temperatures) can be achieved, which is reflected in the hue binning system. This phosphor-converted white LED technology offers a good balance of efficacy, color quality, and manufacturability.

13. Technology Development Trends

The trend in SMD LEDs for consumer electronics is unequivocally towards miniaturization and increased efficiency. The 0.55mm height of this product is a direct response to the demand for thinner devices. Future developments may push this even lower. Concurrently, there is a drive to increase luminous efficacy (lumens per watt) to deliver more light from the same or less electrical power, improving battery life in portable devices. Another trend is improved color rendering and consistency, leading to tighter binning specifications. Furthermore, integration is a key trend, with LEDs incorporating built-in drivers, controllers, or even sensors into the package. While this datasheet describes a discrete component, the underlying InGaN and phosphor technologies continue to advance, enabling these improvements in performance and integration.