LTW-C193SS2 SMD LED Datasheet - Dimensions 0.4mm Thin - Forward Voltage 2.5-2.9V - White Color - 35mW Power - English Technical Document

1. Product Overview

The LTW-C193SS2 is a surface-mount device (SMD) light-emitting diode (LED) designed for modern, compact electronic applications. It is characterized by its exceptionally thin profile, measuring only 0.40 mm in height, making it suitable for applications with severe space constraints. The device utilizes an InGaN (Indium Gallium Nitride) semiconductor material to produce white light, offering high brightness levels. It is packaged on 8mm tape wound onto 7-inch diameter reels, facilitating compatibility with high-speed automated pick-and-place assembly equipment commonly used in electronics manufacturing.

This LED is classified as a green product and complies with the Restriction of Hazardous Substances (RoHS) directive. Its design is compatible with standard infrared (IR) reflow soldering processes, which is the predominant method for attaching surface-mount components to printed circuit boards (PCBs). The package conforms to Electronic Industries Alliance (EIA) standards, ensuring mechanical compatibility with industry-standard placement systems.

2. Technical Parameter Deep-Dive

2.1 Absolute Maximum Ratings

The absolute maximum ratings define the limits beyond which permanent damage to the device may occur. For the LTW-C193SS2, these are specified at an ambient temperature (Ta) of 25°C. The maximum continuous power dissipation is 35 milliwatts (mW). The DC forward current should not exceed 10 mA under continuous operation. For pulsed operation, a peak forward current of 50 mA is permissible, but only under specific conditions: a duty cycle of 1/10 (10%) and a pulse width of 0.1 milliseconds. Exceeding these current limits can lead to excessive junction temperature, accelerated degradation of the semiconductor material, and catastrophic failure.

The device is rated for an operating temperature range of -20°C to +80°C. The storage temperature range is wider, from -40°C to +85°C, indicating the conditions under which the LED can be kept without applied power. A critical note specifies that operating the LED under reverse bias conditions in an application circuit may cause damage or failure. Therefore, circuit designs must ensure the LED is not subjected to reverse voltage during normal use.

2.2 Electrical & Optical Characteristics

The electrical and optical characteristics are measured at a standard test condition of Ta=25°C and a forward current (IF) of 2 mA, which serves as a common reference point for comparing LED performance.

• Luminous Intensity (Iv): This parameter measures the perceived brightness of the light output by the human eye. The Iv for the LTW-C193SS2 has a minimum value of 18.0 millicandelas (mcd) and a maximum (typical) of 71.0 mcd at 2mA. The actual Iv value for a specific unit is classified and marked on its packaging bag.
• Viewing Angle (2θ1/2): Defined as the full angle at which the luminous intensity is half of the intensity at 0 degrees (on-axis). This LED features a wide viewing angle of 130 degrees, providing a broad, diffuse light pattern suitable for backlighting and indicator applications.
• Chromaticity Coordinates (x, y): These coordinates define the color point of the white light on the CIE 1931 chromaticity diagram. The typical values are x=0.29 and y=0.31. A tolerance of ±0.01 is applied to these coordinates. The color is measured using a spectrometer that approximates the CIE standard observer eye-response curve.
• Forward Voltage (VF): The voltage drop across the LED when conducting the specified forward current. At IF=2mA, VF ranges from a minimum of 2.50 volts to a maximum of 2.90 volts. This parameter is important for designing the current-limiting circuitry for the LED.
• Reverse Current (IR): The small leakage current that flows when a reverse voltage is applied. It is specified as a maximum of 10 microamperes (μA) at a reverse voltage (VR) of 5V. The datasheet explicitly states this test condition is for characterization only and that the device is not designed for reverse operation.

The datasheet includes important cautionary notes regarding Electrostatic Discharge (ESD). LEDs are sensitive to ESD, and handling procedures should include the use of wrist straps, anti-static gloves, and properly grounded equipment to prevent damage.

3. Binning System Explanation

To manage natural variations in the semiconductor manufacturing process, LEDs are sorted into performance bins. The LTW-C193SS2 uses a three-dimensional binning system based on Forward Voltage (VF), Luminous Intensity (Iv), and Hue (Chromaticity).

3.1 Forward Voltage (VF) Bins

LEDs are categorized into four VF bins (Y1, Y2, Y3, Y4), each representing a 0.1V range within the overall 2.50V to 2.90V specification. For example, bin Y1 includes LEDs with VF between 2.50V and 2.60V at IF=2mA. A tolerance of ±0.1V is applied to each bin. Consistent VF within a batch helps ensure uniform brightness when LEDs are driven by a constant-voltage source or in simple parallel configurations (though constant-current driving is strongly recommended).

3.2 Luminous Intensity (Iv) Bins

Three Iv bins (M, N, P) are defined. Bin M covers the range 18.0-28.0 mcd, bin N covers 28.0-45.0 mcd, and bin P covers 45.0-71.0 mcd, all measured at IF=2mA. A tolerance of ±15% is associated with each bin. Selecting LEDs from the same Iv bin is crucial for applications requiring uniform brightness, such as multi-LED backlight arrays or status indicator panels.

3.3 Hue (Chromaticity) Bins

The white color point is binned into six regions (S1 through S6) on the CIE 1931 chromaticity diagram. Each bin is defined by a quadrilateral area specified by four sets of (x, y) coordinates. For instance, bin S2 covers coordinates approximately between x:0.274-0.294 and y:0.258-0.319. A diagram in the datasheet visually plots these bins. A tolerance of ±0.01 applies to the (x, y) coordinates. Using LEDs from the same hue bin is essential to avoid visible color differences in multi-LED applications.

4. Mechanical & Packaging Information

4.1 Package Dimensions

The LED features a standard chip LED package format. Key dimensions include the overall height of 0.40 mm. The datasheet provides a detailed dimensional drawing with all critical measurements, including pad spacing, component width, and lens size. All dimensions are provided in millimeters, with a general tolerance of ±0.10 mm unless otherwise specified. A note indicates that the cathode identification mark (a white mark) may be partially covered by the lens, so careful orientation during placement is necessary.

4.2 Suggested Soldering Pad Layout

A recommended land pattern (footprint) for the PCB is provided to ensure reliable solder joint formation during reflow. The suggested pad dimensions and spacing are given to achieve proper solder fillets and mechanical strength. A note recommends a maximum stencil thickness of 0.10 mm for solder paste application to prevent excessive solder paste deposition and potential bridging.

4.3 Tape and Reel Packaging

The LEDs are supplied in embossed carrier tape with a protective cover tape, wound onto 7-inch (178 mm) diameter reels. The tape width is 8 mm. Standard reel capacity is 5000 pieces. The packaging conforms to ANSI/EIA 481-1 specifications. Key packaging notes include: empty pockets are sealed with cover tape; the minimum order quantity for remnants is 500 pieces; and a maximum of two consecutive missing components (empty pockets) is allowed per reel.

5. Soldering & Assembly Guidelines

5.1 Reflow Soldering Profile

The LED is compatible with infrared reflow soldering. The absolute maximum soldering condition is 260°C peak temperature for a maximum of 10 seconds. A suggested reflow profile is provided, which typically includes a pre-heat stage, a temperature ramp, a peak reflow zone, and a cooling period. The datasheet emphasizes that the optimal profile depends on the specific PCB design, solder paste, and oven used, and recommends board-level characterization.

5.2 Hand Soldering

If hand soldering is necessary, it should be performed with extreme care. The recommended maximum soldering iron tip temperature is 300°C, with a maximum soldering time of 3 seconds per joint. Hand soldering should be performed only once to avoid thermal stress damage to the LED package.

5.3 Cleaning

Cleaning after soldering should be done with care. Only specified cleaning agents should be used. The datasheet recommends using ethyl alcohol or isopropyl alcohol at room temperature. The LED should be immersed for less than one minute. Unspecified chemical liquids may damage the plastic package or lens material.

6. Storage & Handling

Storage for Sealed Packages: LEDs in their original, unopened moisture-proof packaging (with desiccant) should be stored at 30°C or less and 90% relative humidity (RH) or less. The shelf life under these conditions is one year.

Storage for Opened Packages: Once the moisture-proof bag is opened, the LEDs are sensitive to ambient moisture. The storage environment should not exceed 30°C and 60% RH. It is strongly recommended that LEDs removed from their original packaging be subjected to IR reflow soldering within 672 hours (28 days).

Extended Storage & Baking: For storage beyond 672 hours outside the original bag, LEDs should be kept in a sealed container with desiccant or in a nitrogen desiccator. If LEDs have been exposed to ambient conditions for more than 672 hours, they must be baked at approximately 60°C for at least 20 hours prior to soldering to remove absorbed moisture and prevent \"popcorning\" (package cracking) during reflow.

7. Application Suggestions & Design Considerations

7.1 Typical Application Scenarios

The ultra-thin profile (0.4mm) makes this LED ideal for applications where vertical space is critical. Primary applications include: ultra-slim backlighting for mobile devices (phones, tablets), wearable electronics, status indicators in compact consumer electronics, and panel illumination in thin industrial control interfaces. Its wide viewing angle is beneficial for applications requiring even, diffuse illumination rather than a focused beam.

7.2 Circuit Design Considerations

• Current Driving: Always drive LEDs with a constant current source, not a constant voltage source, to ensure stable light output and prevent thermal runaway. The recommended operating current is at or below the 10 mA DC maximum.
• Current Limiting Resistor: When using a simple voltage source with a series resistor, calculate the resistor value using the formula R = (V_supply - VF_LED) / I_desired. Use the maximum VF from the datasheet (2.9V) for a conservative design to ensure the current does not exceed the desired value.
• ESD Protection: Incorporate ESD protection diodes on PCB lines connected to the LED anode/cathode if the assembly or end-product is likely to be handled in non-ESD-controlled environments.
• Thermal Management: Although power dissipation is low, ensure adequate thermal relief in the PCB pads, especially if multiple LEDs are placed closely together or if the ambient temperature is high. This helps maintain a lower junction temperature, which preserves LED lifetime and color stability.

7.3 Optical Design Considerations

For indicator applications, consider the wide 130-degree viewing angle. Light guides or diffusers may be needed to shape the light output or hide the discrete LED point source. For backlighting, the binning selection (Iv and Hue) is paramount. Use LEDs from a single, tight bin to achieve uniform brightness and color across the display or panel.

8. Reliability & Lifespan Factors

While the datasheet does not provide a specific L70 or L50 lifetime rating (hours to 70% or 50% lumen maintenance), the lifetime of an LED is primarily influenced by its operating junction temperature. Key factors affecting reliability include:

• Operating Current: Driving the LED at or below its rated current (10mA DC) is essential. Operating above this rating exponentially increases junction temperature and accelerates lumen depreciation and color shift.
• Ambient Temperature: Operating near the upper limit of the specified range (+80°C) will reduce the effective lifetime. Derating the operating current at higher ambient temperatures is a good practice.
• Solder Process Adherence: Following the recommended reflow profile and avoiding excessive hand soldering heat prevents internal wire bond damage and package delamination, which are common failure modes.
• ESD and Electrical Overstress: Proper handling and circuit protection prevent immediate catastrophic failure or latent damage that manifests as early failure in the field.

9. Technical Comparison & Market Context

The LTW-C193SS2 belongs to the category of ultra-thin chip LEDs. Its primary differentiating feature is its 0.40mm height. Compared to standard 0603 or 0402 package LEDs which are typically 0.6-0.8mm tall, this device offers a significant reduction in profile. The InGaN technology for white light typically offers higher efficiency and better color rendering options compared to older technologies like phosphor-converted blue on a different substrate. The wide 130-degree viewing angle is standard for chip LEDs without a built-in lens and is suitable for many general-purpose lighting applications. The key selection criteria against competing products would be the specific combination of thickness, brightness (Iv at a given current), forward voltage, and the granularity of its binning system, which allows for precise color and brightness matching in demanding applications.