Dual Color SMD LED LTST-C195TBKSKT Datasheet - Package 0.55mm Thin - Blue 3.8V / Yellow 2.4V - 76mW/62.5mW Power - English Technical Document

1. Product Overview

This document details the specifications for a dual-color, surface-mount device (SMD) LED. The component integrates two distinct semiconductor chips within a single, exceptionally thin package, enabling compact designs where space is at a premium. The primary application is as an indicator or status light in electronic equipment, offering two distinct colors from one device footprint.

1.1 Core Advantages and Target Market

The device's defining feature is its ultra-thin profile of 0.55mm, which is a critical advantage for modern, slim consumer electronics, portable devices, and densely packed PCBs. It utilizes advanced semiconductor materials: an InGaN (Indium Gallium Nitride) chip for blue emission and an AlInGaP (Aluminum Indium Gallium Phosphide) chip for yellow emission. These materials are known for their high efficiency and brightness. The LED is fully compliant with RoHS (Restriction of Hazardous Substances) directives. It is packaged on 8mm tape on 7-inch diameter reels, making it fully compatible with high-speed, automated pick-and-place assembly equipment used in volume manufacturing. The device is also designed to withstand standard infrared (IR) reflow soldering processes used for lead-free (Pb-free) solder assembly.

2. In-Depth Technical Parameter Analysis

The following sections provide a detailed breakdown of the device'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.

• Power Dissipation (Pd): The maximum allowable power the LED can dissipate as heat. The Blue chip is rated for 76 mW, while the Yellow chip is rated for 62.5 mW. Exceeding this can lead to overheating and accelerated degradation.
• Peak Forward Current (I_FP): The maximum pulsed current (1/10 duty cycle, 0.1ms pulse width). The Blue chip can handle 100 mA pulses, and the Yellow chip 60 mA. This parameter is important for brief, high-intensity flashing applications.
• DC Forward Current (I_F): The maximum continuous forward current for reliable long-term operation. It is 20 mA for the Blue chip and 25 mA for the Yellow chip. This is the standard driving current for most brightness specifications.
• Temperature Ranges: The device is rated for operation between -20°C to +80°C and can be stored between -30°C to +100°C.
• Soldering Condition: The component can withstand IR reflow soldering with a peak temperature of 260°C for a maximum of 10 seconds, which aligns with common Pb-free process profiles.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured at the recommended DC forward current of 20 mA.

• Luminous Intensity (I_V): A measure of the perceived brightness. For the Blue chip, the typical intensity ranges from a minimum of 28.0 mcd to a maximum of 180.0 mcd. For the Yellow chip, the range is from 45.0 mcd to 280.0 mcd. The actual value is binned (see Section 3).
• Viewing Angle (2θ_1/2): The angular span at which the luminous intensity is at least half of the intensity at 0° (on-axis). Both colors have a typical wide viewing angle of 130 degrees, providing good visibility from side angles.
• Peak Wavelength (λ_P): The wavelength at which the optical output power is maximum. Typical values are 468 nm (Blue) and 591 nm (Yellow).
• Dominant Wavelength (λ_d): The single wavelength that best describes the perceived color of the light. Typical values are 470 nm (Blue) and 589 nm (Yellow). This is derived from the CIE chromaticity diagram.
• Spectral Bandwidth (Δλ): The width of the emitted spectrum at half its maximum power. Both chips have a typical bandwidth of 25 nm, indicating relatively pure color emission.
• Forward Voltage (V_F): The voltage drop across the LED when driven at 20 mA. The Blue chip has a typical V_F of 3.30V (max 3.80V), and the Yellow chip has a typical V_F of 2.00V (max 2.40V). This is crucial for driver circuit design and power supply selection.
• Reverse Current (I_R): The maximum leakage current when a reverse bias of 5V is applied. It is 10 μA for both chips. Critical Note: The device is not designed for reverse operation; applying reverse voltage beyond the test condition can cause immediate failure.

2.3 Thermal Considerations

While not explicitly detailed in thermal resistance (θ_JA), the power dissipation ratings and operating temperature range are the primary thermal constraints. Effective PCB layout with adequate copper pour for heat sinking is essential to maintain junction temperature within safe limits, especially when driving at or near the maximum DC current. Exceeding the maximum junction temperature will drastically reduce the LED's lifespan.

3. Binning System Explanation

To account for natural variations in semiconductor manufacturing, LEDs are sorted into performance bins. This ensures consistency within a production batch.

3.1 Luminous Intensity Binning

The luminous output is categorized into bins defined by minimum and maximum values. Each bin has a tolerance of ±15%.

Blue Chip Bins:
N: 28.0 - 45.0 mcd
P: 45.0 - 71.0 mcd
Q: 71.0 - 112.0 mcd
R: 112.0 - 180.0 mcd

Yellow Chip Bins:
P: 45.0 - 71.0 mcd
Q: 71.0 - 112.0 mcd
R: 112.0 - 180.0 mcd
S: 180.0 - 280.0 mcd

Designers must specify the required bin codes when ordering to guarantee the brightness level needed for their application. Using a lower bin (e.g., N for blue) may result in a dimmer display.

4. Performance Curve Analysis

The datasheet references typical characteristic curves which are essential for understanding device behavior under non-standard conditions. While the specific graphs are not reproduced in the text, their implications are described below.

4.1 Forward Current vs. Forward Voltage (I-V Curve)

This curve shows the non-linear relationship between current and voltage. For both LED chips, the voltage increases logarithmically with current. The typical V_F values provided are specific to 20 mA. Driving at a lower current will result in a lower V_F, and driving higher will increase V_F and power dissipation. A constant-current driver is highly recommended over a constant-voltage driver to ensure stable brightness and prevent thermal runaway.

4.2 Luminous Intensity vs. Forward Current

This graph illustrates how light output increases with forward current. It is generally close to linear within the operating range but will saturate at very high currents due to efficiency droop and thermal effects. The 20 mA drive current is chosen as a standard point that balances brightness, efficiency, and reliability.

4.3 Luminous Intensity vs. Ambient Temperature

LED light output decreases as the junction temperature rises. This curve is critical for applications operating in high-temperature environments. The derating factor (percentage decrease in output per degree Celsius) can be estimated from this graph. Adequate heat sinking is necessary to minimize brightness loss over temperature.

4.4 Spectral Distribution

These curves plot relative intensity against wavelength, showing the peak wavelength (λ_P) and the spectral bandwidth (Δλ). The narrow 25 nm bandwidth for both colors confirms good color purity, which is desirable for indicator applications where color distinction is important.

5. Mechanical and Package Information

5.1 Package Dimensions and Pin Assignment

The device conforms to an EIA standard package outline. The key mechanical feature is the overall height of 0.55mm. The pin assignment for the dual-color chip is as follows: Pins 1 and 3 are for the Blue (InGaN) chip, and Pins 2 and 4 are for the Yellow (AlInGaP) chip. This four-pad design provides separate electrical connections for each color, allowing them to be controlled independently.

5.2 Recommended Soldering Pad Layout

A suggested land pattern (footprint) for PCB design is provided. Adhering to this pattern is crucial for achieving reliable solder joints during reflow, ensuring proper alignment, and facilitating heat transfer away from the LED. The pad dimensions are designed to prevent tombstoning (component standing up on one end) during solder reflow.

5.3 Polarity Identification

While not explicitly shown in the text, SMD LEDs typically have a marking on the package (such as a dot, notch, or beveled edge) to indicate the cathode (-) or a specific pin. The datasheet's pin assignment table must be cross-referenced with the package marking diagram (implied by \"Package Dimensions\") for correct orientation during assembly and design.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Profile

A suggested temperature profile for lead-free reflow soldering is included. Key parameters include:
- Pre-heat: Ramp from ambient to 150-200°C.
- Soak/Pre-heat Time: Maximum of 120 seconds to activate flux and minimize thermal shock.
- Peak Temperature: Maximum of 260°C.
- Time Above Liquidus (TAL): The time spent above the solder's melting point (typically ~217°C for SnAgCu) should be sufficient for proper joint formation but minimized to reduce thermal stress on the LED. The profile is designed to be compliant with JEDEC standards.

6.2 Hand Soldering

If manual rework is necessary, a soldering iron temperature must not exceed 300°C, and the contact time should be limited to a maximum of 3 seconds per joint. This should be performed only once to avoid damaging the plastic package and the internal wire bonds.

6.3 Storage and Handling Conditions

Moisture Sensitivity: The LEDs are packaged in a moisture-barrier bag with desiccant. Once the original sealed bag is opened, the components are exposed to ambient humidity.
- Opened Package Storage: Should not exceed 30°C and 60% Relative Humidity (RH).
- Floor Life: It is recommended to complete IR reflow within one week of opening the bag.
- Extended Storage: For storage beyond one week, components should be kept in a sealed container with desiccant or in a nitrogen desiccator.
- Baking: Components stored out of their original packaging for more than one week must be baked at approximately 60°C for at least 20 hours before soldering to remove absorbed moisture and prevent \"popcorning\" (package cracking due to vapor pressure during reflow).

6.4 Cleaning

If post-solder cleaning is required, only specified solvents should be used. Unspecified chemicals may damage the plastic lens or package material. Acceptable cleaners include ethyl alcohol or isopropyl alcohol (IPA). The LED should be immersed at normal temperature for less than one minute.

6.5 Electrostatic Discharge (ESD) Precautions

LEDs, like most semiconductor devices, are susceptible to damage from electrostatic discharge. Handling precautions are mandatory: use grounded wrist straps, anti-static gloves, and ensure all equipment and work surfaces are properly grounded.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The components are supplied on embossed carrier tape for automated assembly.
- Carrier Tape Width: 8 mm.
- Reel Diameter: 7 inches.
- Quantity per Reel: 4000 pieces.
- Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
- Pocket Sealing: Empty pockets are sealed with cover tape.
- Missing Components: A maximum of two consecutive missing LEDs (empty pockets) is allowed per the specification.
- Standard: Packaging follows ANSI/EIA-481 specifications.

7.2 Part Number Interpretation

The part number LTST-C195TBKSKT likely encodes specific attributes, though the full breakdown isn't provided in this excerpt. Typically, such codes indicate the series (LTST), size/profile (C195), color (TB for dual color Blue/Yellow), and packaging (KSKT likely referring to tape and reel). The exact bin codes for luminous intensity must be specified separately when ordering.

8. Application Notes and Design Considerations

8.1 Typical Application Scenarios

This dual-color LED is ideal for multi-status indicators. Common uses include:
- Power/Status Indicators: Blue for \"standby\" or \"on,\" Yellow for \"charging\" or \"warning.\"
- Network Equipment: Indicating link status, activity, or speed.
- Consumer Electronics: Battery level indicators, mode selection feedback on compact devices.
- Industrial Controls: Machine state indication (running, fault, idle).
The ultra-thin profile makes it particularly suitable for smartphones, tablets, ultrabooks, and other space-constrained portable devices.

8.2 Circuit Design Considerations

1. Current Limiting: Always use a series current-limiting resistor or a dedicated constant-current LED driver IC for each color channel. Calculate the resistor value using R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet to ensure current does not exceed limits even with part-to-part variation.
2. Independent Control: The separate anode/cathode for each color allows for independent PWM (Pulse Width Modulation) dimming or blinking control via a microcontroller.
3. Power Dissipation: Verify that the total power (I_F * V_F for each chip) does not exceed the individual chip's power rating, especially if both are driven simultaneously.
4. Reverse Voltage Protection: Although not a Zener diode, a small-signal diode in parallel with each LED (cathode to anode) can provide protection against accidental reverse voltage transients on the PCB.

8.3 PCB Layout Recommendations

- Follow the recommended solder pad dimensions precisely.
- Use thermal relief connections for the LED pads if they are connected to large ground/power planes to facilitate soldering while still providing some thermal conduction.
- For optimal heat dissipation, consider adding small vias under or near the thermal pad (if present) to conduct heat to inner or bottom PCB layers.

9. Technical Comparison and Differentiation

Compared to older dual-color LEDs or using two discrete single-color LEDs, this device offers distinct advantages:
- Space Savings: A single 0.55mm thin package replaces two components, saving PCB area and volume.
- Simplified Assembly: One pick-and-place operation instead of two, increasing assembly throughput and reducing potential placement errors.
- Material Technology: Use of InGaN and AlInGaP chips typically offers higher efficiency and brightness compared to older technologies like GaP.
- Process Compatibility: Full compatibility with standard, high-volume SMT assembly and Pb-free reflow processes reduces manufacturing complexity.

10. Frequently Asked Questions (FAQs) Based on Technical Parameters

Q1: Can I drive both the Blue and Yellow LEDs at the same time?
A: Yes, electrically they are independent. However, you must ensure that the power dissipation for each chip is not exceeded and that the PCB/local ambient temperature remains within the operating range. The total heat generated will be the sum of both.

Q2: What happens if I connect the polarity incorrectly?
A: Applying significant reverse voltage (beyond the 5V test condition) will likely cause immediate and catastrophic failure of the LED chip due to reverse breakdown. Always observe correct polarity.

Q3: Why is the forward voltage different for Blue and Yellow?
A: Forward voltage is a fundamental property of the semiconductor material's bandgap. InGaN (Blue) has a wider bandgap than AlInGaP (Yellow), requiring a higher voltage to \"push\" electrons across the junction, resulting in higher-energy (shorter wavelength) photons.

Q4: How do I select the right current-limiting resistor?
A: Use the formula R = (V_supply - V_F) / I_F. For reliability, use the maximum V_F from the datasheet (3.80V for Blue, 2.40V for Yellow) and your desired I_F (e.g., 20mA). For a 5V supply: R_Blue = (5 - 3.8) / 0.02 = 60 Ω; R_Yellow = (5 - 2.4) / 0.02 = 130 Ω. Use the next higher standard resistor value.

Q5: The LED seems dimmer than expected. What could be wrong?
A: 1) Verify you are using the correct bin code; a lower bin (e.g., N for blue) is less bright. 2) Check the actual forward current with a multimeter; a miscalculated resistor or low supply voltage can reduce current. 3) Ensure the LED is not overheated; high junction temperature reduces light output. 4) Confirm the viewing angle; brightness is measured on-axis.

11. Practical Design and Usage Examples

Example 1: Dual-Status USB Port Indicator. In a laptop, this LED can be placed next to a USB-C port. It can be driven by the embedded controller (EC): Blue solid when a device is connected and active, Yellow blinking when the port is supplying charging current, and both off otherwise. The thin profile allows it to fit within the tight bezel.

Example 2: IoT Device Status. In a compact wireless sensor, the LED can indicate network state: Blue for \"connected to cloud,\" Yellow for \"data transmitting,\" and alternating colors for \"error.\" The low power consumption is suitable for battery-operated devices, and the wide viewing angle ensures visibility from various angles.

Example 3: Handling Moisture-Sensitive Components. A manufacturer receives a reel. They use the entire reel in one production shift. If a partial reel remains, they store it in a sealed container with desiccant. Two weeks later, before using the remainder, they bake the reel at 60°C for 24 hours before loading it into the pick-and-place machine, following the datasheet guidelines to prevent soldering defects.

12. Operational 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 from the n-type material recombine with holes from the p-type material. This recombination releases energy in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the energy bandgap of the semiconductor material. The InGaN chip has a bandgap corresponding to blue light (~470 nm), while the AlInGaP chip has a bandgap corresponding to yellow light (~589 nm). The plastic package serves to protect the delicate semiconductor die and wire bonds, shape the light output beam (lens), and provide the physical form factor for mounting.

13. Technology Trends and Developments

The device described reflects several ongoing trends in LED technology:
- Miniaturization: The drive towards 0.55mm and thinner packages continues to enable sleeker product designs.
- High-Efficiency Materials: InGaN and AlInGaP represent mature, high-performance material systems for visible LEDs, offering good efficacy (lumens per watt) for indicator applications.
- Integration: Combining multiple functions (two colors) into a single package is part of a broader trend of component integration to save space and simplify assembly.
- Robust Manufacturing Compatibility: The emphasis on tape-and-reel packaging, IR reflow tolerance, and moisture sensitivity classification aligns with the needs of fully automated, high-volume electronics manufacturing. Future developments may include even thinner packages, integrated current-limiting resistors (LED \"modules\"), or three-color (RGB) chips in a similar footprint, driven by demands from the consumer electronics and automotive sectors.