LTST-C295TBKFKT Dual Color SMD LED Datasheet - 0.55mm Thin - Blue 3.8V / Orange 2.4V - 76mW / 75mW - English Technical Document

1. Product Overview

The LTST-C295TBKFKT is a dual-color, surface-mount device (SMD) LED designed for modern electronic applications requiring compact size and high brightness. This product integrates two distinct semiconductor chips within a single, exceptionally thin package.

1.1 Core Advantages and Target Market

This LED's primary advantage is its ultra-thin profile of 0.55mm, making it suitable for space-constrained applications like ultra-slim displays, mobile devices, and backlighting modules. It meets ROHS and green product standards, ensuring environmental compliance. The use of advanced InGaN (for blue) and AlInGaP (for orange) chip technologies provides high luminous efficiency. Its compatibility with automatic placement equipment and infrared reflow soldering processes aligns it with high-volume, automated manufacturing lines typical in consumer electronics, industrial indicators, and automotive interior lighting.

2. In-Depth Technical Parameter Analysis

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

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. They are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): Blue: 76 mW, Orange: 75 mW. This parameter indicates the maximum power the LED can dissipate as heat without degradation.
• Peak Forward Current (I_FP): Blue: 100 mA, Orange: 80 mA (at 1/10 duty cycle, 0.1ms pulse width). This is the maximum instantaneous current for pulsed operation.
• DC Forward Current (I_F): Blue: 20 mA, Orange: 30 mA. This is the maximum continuous current for reliable operation.
• Temperature Ranges: Operating: -20°C to +80°C; Storage: -30°C to +100°C.
• Soldering: Withstands infrared reflow at 260°C for 10 seconds, compatible with lead-free (Pb-free) processes.

2.2 Electrical and Optical Characteristics

These are typical performance parameters measured at Ta=25°C and I_F=20 mA, unless stated otherwise.

• Luminous Intensity (I_V): A key measure of brightness. For the Blue chip, it ranges from a minimum of 28.0 mcd to a maximum of 180.0 mcd. For the Orange chip, it ranges from 45.0 mcd to 280.0 mcd. The actual value is determined by the bin code (see Section 3).
• Viewing Angle (2θ_1/2): 130 degrees for both colors. This wide viewing angle makes the LED suitable for applications requiring broad illumination or visibility from various angles.
• Peak Wavelength (λ_P): Blue: 468 nm (typical), Orange: 611 nm (typical). This is the wavelength at which the emitted light intensity is highest.
• Dominant Wavelength (λ_d): Blue: 470 nm (typical), Orange: 605 nm (typical). This is the single wavelength perceived by the human eye, defining the color.
• Spectral Line Half-Width (Δλ): Blue: 25 nm, Orange: 17 nm. This indicates the color purity; a smaller value means a more monochromatic light.
• Forward Voltage (V_F): Blue: 3.80 V (max), Orange: 2.40 V (max). This is the voltage drop across the LED when operating at the specified current. The difference is due to the different semiconductor materials.
• Reverse Current (I_R): 10 μA (max) for both at V_R=5V. LEDs are not designed for reverse bias operation; this parameter is for leakage current testing only.

3. Binning System Explanation

To ensure consistent color and brightness, LEDs are sorted into bins based on measured performance.

3.1 Luminous Intensity Binning

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

• Blue Color 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).
• Orange Color 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).

This system allows designers to select LEDs with guaranteed minimum brightness for their application, ensuring uniformity in multi-LED designs.

4. Performance Curve Analysis

While specific graphs are not detailed in the provided text, typical curves for such devices would include:

• I-V (Current-Voltage) Curve: Shows the relationship between forward voltage (V_F) and forward current (I_F). It is exponential, characteristic of a diode.
• Luminous Intensity vs. Forward Current: Shows how light output increases with current, typically in a near-linear relationship within the operating range.
• Luminous Intensity vs. Ambient Temperature: Shows the derating of light output as junction temperature increases. High-power or high-current operation requires thermal management to maintain brightness.
• Spectral Distribution: A graph plotting light intensity against wavelength, showing the peak and dominant wavelengths and the spectral width.

5. Mechanical and Package Information

5.1 Package Dimensions and Pin Assignment

The device conforms to EIA standard package dimensions. The pin assignment is crucial for correct circuit design:

• Pins 1 and 3 are assigned to the Blue (InGaN) chip.
• Pins 2 and 4 are assigned to the Orange (AlInGaP) chip.

Detailed dimensioned drawings (not reproduced here) would specify the exact length, width, height, lead spacing, and positioning tolerances. The lens is water clear.

5.2 Recommended Soldering Pad Layout

A suggested land pattern (solder pad design) for the PCB is provided to ensure reliable solder joint formation during reflow, proper alignment, and sufficient mechanical strength.

6. Soldering, Assembly, and Handling Guidelines

6.1 Reflow Soldering Profile

A suggested infrared (IR) reflow profile for lead-free processes is provided. Key parameters include:

• Pre-heat: 150-200°C for a maximum of 120 seconds to gradually heat the board and components, activating flux and minimizing thermal shock.
• Peak Temperature: Maximum of 260°C. The LED can withstand this temperature for a maximum of 10 seconds. The profile on page 3 of the datasheet serves as a generic target based on JEDEC standards.

6.2 Cleaning

If cleaning is necessary after soldering, only specified solvents should be used to avoid damaging the plastic package. Immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute is recommended. Unspecified chemicals must be avoided.

6.3 Storage and Moisture Sensitivity

LEDs are sensitive to moisture absorption, which can cause \"popcorning\" (package cracking) during reflow.

• Sealed Package: Store at ≤30°C and ≤90% RH. Use within one year.
• Opened Package: Store at ≤30°C and ≤60% RH. Reflow within one week. For longer storage, use a sealed container with desiccant or a nitrogen ambient. If stored opened for >1 week, bake at ~60°C for at least 20 hours before soldering.

6.4 Electrostatic Discharge (ESD) Precautions

Static electricity can damage the LED chip. It is recommended to use a wrist strap or anti-static gloves when handling. All equipment and workstations must be properly grounded.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied in industry-standard packaging for automated assembly:

• Packed in 8mm wide embossed carrier tape.
• Reeled onto 7-inch (178mm) diameter reels.
• Standard reel contains 4000 pieces.
• Minimum order quantity for remainders is 500 pieces.
• Packaging complies with ANSI/EIA-481 specifications.

8. Application Notes and Design Considerations

8.1 Typical Application Scenarios

• Status Indicators: Dual-color capability allows for multiple status signals (e.g., power on/standby, network activity, charge status).
• Backlighting: For keypads, icons, or small display panels, especially where thickness is critical.
• Consumer Electronics: Mobile devices, wearables, gaming peripherals.
• Automotive Interior Lighting: Dashboard indicators, switch backlighting.

8.2 Circuit Design Considerations

• Current Limiting: Always use a series resistor or constant current driver to limit the forward current to the specified DC value (20mA for Blue, 30mA for Orange). Operating above this reduces lifetime and reliability.
• Independent Control: The separate anode/cathode pins for each color allow them to be controlled independently by two different driver circuits.
• Thermal Management: Although power dissipation is low, ensuring adequate PCB copper area or thermal vias can help maintain lower junction temperature, preserving luminous output and longevity.
• Reverse Voltage Protection: The device is not designed for reverse operation. Ensure circuit design prevents the application of reverse bias exceeding 5V.

9. Technical Comparison and Differentiation

The primary differentiating factors of this LED are:

• Ultra-Thin Package (0.55mm): This is a significant advantage over standard SMD LEDs (often 0.6mm-1.2mm thick) for ultra-slim designs.
• Dual-Chip, Dual-Color in One Package: Saves PCB space and simplifies assembly compared to using two separate single-color LEDs.
• Material Combination: Uses high-efficiency InGaN for blue and AlInGaP for orange/red, which typically offer higher brightness and better temperature stability than older technologies like GaP.
• Full Process Compatibility: Designed for modern, high-volume SMT lines with pick-and-place and lead-free reflow soldering.

10. Frequently Asked Questions (FAQs)

Q: Can I drive both colors simultaneously at their maximum DC current?

A: No. The Absolute Maximum Ratings are for individual chips. Driving both simultaneously would exceed the total thermal capacity of the package. Derate the currents or use pulsed operation if both need to be on.

Q: What is the difference between Peak Wavelength and Dominant Wavelength?

A> Peak Wavelength (λ_P) is the physical peak of the emission spectrum. Dominant Wavelength (λ_d) is calculated from the CIE color coordinates and represents the perceived color. They are often close but not identical.

Q: How do I interpret the bin code in the part number?

A: The bin code (e.g., the letters in the part number suffix) specifies the guaranteed minimum luminous intensity for each color. Consult the bin code list in the datasheet to select the appropriate brightness grade for your application.

Q: Is a heat sink required?

A: For continuous operation at maximum DC current, careful thermal design of the PCB (using copper pours as heat spreaders) is recommended. For pulsed operation or lower currents, it may not be necessary.

11. Practical Application Example

Scenario: Designing a dual-status indicator for a portable device.

The LED can indicate charging (Orange) and fully charged (Blue). The microcontroller would sink current through the appropriate LED via a GPIO pin and a current-limiting resistor. The resistor value is calculated using Ohm's Law: R = (V_supply - V_{F_LED}) / I_F. For a 5V supply and the Blue LED (V_F~3.2V typical, I_F=20mA): R = (5 - 3.2) / 0.02 = 90 Ohms. A standard 91-ohm resistor would be used. The ultra-thin profile allows it to fit behind a slim bezel.

12. Operating Principle Introduction

An LED is a semiconductor diode. When a forward voltage is applied across the p-n junction, electrons and holes recombine, releasing energy in the form of photons (light). The color (wavelength) of the light is determined by the energy bandgap of the semiconductor material. InGaN (Indium Gallium Nitride) has a wider bandgap, emitting shorter wavelength blue light. AlInGaP (Aluminum Indium Gallium Phosphide) has a narrower bandgap, emitting longer wavelength orange/red light. The \"water clear\" lens does not color the light but helps in shaping the beam (viewing angle).

13. Technology Trends

The trend in SMD LEDs for general indication continues towards:

• Increased Efficiency: More lumens per watt (lm/W), reducing power consumption for a given brightness.
• Smaller Footprints and Thinner Profiles: Enabling more compact and sleek end products.
• Higher Reliability and Longer Lifetimes: Improved materials and packaging techniques.
• Better Color Consistency and Binning: Tighter tolerances on wavelength and intensity for uniform appearance in arrays.
• Enhanced Compatibility: With ever-more demanding assembly processes, including higher temperature reflow profiles.

The LTST-C295TBKFKT aligns with these trends through its thin design, use of high-efficiency chip materials, and robust reflow specifications.