LTST-C281TBKT-5A Blue Chip LED Datasheet - 0.35mm Height - 3.15V Max - 76mW - English Technical Documentation

1. Product Overview

The LTST-C281TBKT-5A is a surface-mount device (SMD) chip LED designed for modern, space-constrained electronic applications. Its defining characteristic is an exceptionally low profile, with a package height of just 0.35mm. This makes it suitable for applications where component thickness is a critical design parameter, such as in ultra-thin displays, mobile devices, and backlighting modules.

The device utilizes an InGaN (Indium Gallium Nitride) semiconductor chip, which is known for producing high-efficiency blue light. The LED is encapsulated in a water-clear lens material, which does not diffuse the light, resulting in a focused, high-intensity output. It is packaged on 8mm tape and supplied on standard 7-inch diameter reels, making it fully compatible with high-speed automated pick-and-place assembly equipment used in volume manufacturing.

Key advantages include compliance with RoHS (Restriction of Hazardous Substances) directives, making it an environmentally friendly "Green Product." It is also designed to be compatible with infrared (IR) reflow soldering processes, which is the standard for assembling surface-mount components onto printed circuit boards (PCBs).

2. Technical Parameter Deep-Dive

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. They are not intended for normal operation.

• Power Dissipation (Pd): 76 mW. This is the maximum amount of power the LED package can dissipate as heat without degrading performance or reliability.
• Peak Forward Current (I_FP): 100 mA. This current can only be applied under pulsed conditions, specifically at a 1/10 duty cycle with a pulse width of 0.1ms. Exceeding this can cause instantaneous chip failure.
• DC Forward Current (I_F): 20 mA. This is the maximum continuous forward current recommended for reliable long-term operation.
• Operating Temperature Range (T_opr): -20°C to +80°C. The LED is designed to function within this ambient temperature range.
• Storage Temperature Range (T_stg): -30°C to +100°C.
• Infrared Soldering Condition: Withstands 260°C for 10 seconds, which aligns with typical lead-free (Pb-free) reflow soldering profiles.

2.2 Electrical & Optical Characteristics

These parameters are measured at a standard test condition of an ambient temperature (T_a) of 25°C and a forward current (I_F) of 5mA, unless otherwise specified.

• Luminous Intensity (I_V): Ranges from a minimum of 11.2 mcd to a maximum of 45.0 mcd, with a typical value provided. This measures the perceived brightness of the LED as seen by the human eye.
• Viewing Angle (2θ_1/2): 130 degrees. This wide viewing angle indicates the light is emitted in a broad, lambertian pattern, suitable for area illumination rather than focused spot lighting.
• Peak Emission Wavelength (λ_P): Typically 468 nm. This is the wavelength at which the spectral power output is highest.
• Dominant Wavelength (λ_d): Specified between 470.0 nm and 475.0 nm. This is the single wavelength that best represents the color perceived by the human eye, derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): Typically 25 nm. This indicates the spectral purity; a smaller value would mean a more monochromatic light source.
• Forward Voltage (V_F): Ranges from 2.65V to 3.15V at 5mA. This is the voltage drop across the LED when it is conducting current.
• Reverse Current (I_R): Maximum 10 μA when a reverse voltage (V_R) of 5V is applied. Important: This LED is not designed for reverse-bias operation; this test parameter is for quality assurance only.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins based on key parameters. The LTST-C281TBKT-5A uses a three-dimensional binning system.

3.1 Forward Voltage Binning

Units are in Volts (V) measured at I_F = 5mA. Tolerance on each bin is ±0.1V.

• Bin Code 1: 2.65V (Min) to 2.75V (Max)
• Bin Code 2: 2.75V to 2.85V
• Bin Code 3: 2.85V to 2.95V
• Bin Code 4: 2.95V to 3.05V
• Bin Code 5: 3.05V to 3.15V

This allows designers to select LEDs with closely matched V_F for applications where uniform current sharing in parallel strings is critical.

3.2 Luminous Intensity Binning

Units are in millicandelas (mcd) measured at I_F = 5mA. Tolerance on each bin is ±15%.

• Bin Code L: 11.2 mcd to 18.0 mcd
• Bin Code M: 18.0 mcd to 28.0 mcd
• Bin Code N: 28.0 mcd to 45.0 mcd

This binning ensures a predictable brightness level for the end application.

3.3 Dominant Wavelength Binning

Units are in nanometers (nm) measured at I_F = 5mA. Tolerance is ±1 nm.

• Bin Code AD: 470.0 nm to 475.0 nm

This tight control over color ensures a consistent blue hue across all LEDs in a production run.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Figure 1 for spectral distribution, Figure 5 for viewing angle), the typical behavior can be inferred from the parameters:

• I-V (Current-Voltage) Characteristic: As a semiconductor diode, the LED will exhibit an exponential relationship between forward current and forward voltage. The specified V_F range at 5mA provides a key operating point. Driving the LED with a constant current source is strongly recommended over using a constant voltage to ensure stable light output.
• Temperature Dependence: The luminous intensity of InGaN LEDs typically decreases as the junction temperature increases. While the operating temperature range is up to 80°C, designers should account for thermal management to maintain desired brightness levels, especially when driving at or near the maximum DC current.
• Spectral Shift: The peak and dominant wavelengths may shift slightly with changes in drive current and junction temperature, though the binning system helps mitigate visible color differences.

5. Mechanical & Package Information

5.1 Package Dimensions

The primary mechanical feature is the 0.35mm package height. All other dimensions conform to EIA (Electronic Industries Alliance) standard outlines for this type of chip LED, ensuring compatibility with industry-standard placement equipment and solder pad layouts. Detailed dimensional drawings with tolerances of ±0.10mm are provided in the datasheet for precise PCB footprint design.

5.2 Polarity Identification

The datasheet includes a diagram showing the cathode and anode markings on the LED package. Correct polarity must be observed during assembly, as applying reverse voltage can damage the device.

5.3 Suggested Solder Pad Dimensions

A recommended land pattern (solder pad layout) for the PCB is provided. Following these recommendations is crucial for achieving reliable solder joints, proper alignment during reflow, and effective heat dissipation from the LED terminals.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profile

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

• Pre-heat: Ramp-up to 150-200°C.
• Pre-heat Time: Maximum 120 seconds to allow for uniform heating and activation of solder paste flux.
• Peak Temperature: Maximum 260°C.
• Time Above Liquidus: The LED should be subjected to the peak temperature for a maximum of 10 seconds. The process should not be repeated more than twice.

This profile is based on JEDEC standards to ensure reliable assembly without subjecting the LED package to excessive thermal stress.

6.2 Hand Soldering

If hand soldering is necessary, extreme care must be taken:

• Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per solder joint.
• Frequency: Should be performed only once to avoid thermal damage.

6.3 Cleaning

If cleaning after soldering is required, only specified solvents should be used to avoid damaging the plastic lens or package. Recommended agents are ethyl alcohol or isopropyl alcohol. The LED should be immersed at normal temperature for less than one minute.

6.4 Storage & Handling

• ESD (Electrostatic Discharge) Precautions: LEDs are sensitive to static electricity. Use wrist straps, anti-static mats, and properly grounded equipment during handling.
• Moisture Sensitivity: While in its original sealed moisture-proof bag with desiccant, the LED has a shelf life of one year when stored at ≤30°C and ≤90% RH. Once the bag is opened, the components should be stored at ≤30°C and ≤60% RH.
• Floor Life: It is recommended that components removed from their original packaging be subjected to IR reflow within 672 hours (28 days). For longer storage outside the original bag, use a sealed container with desiccant. Components stored beyond 672 hours should be baked at approximately 60°C for at least 20 hours before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

7. Packaging & Ordering Information

The LTST-C281TBKT-5A is supplied in a tape-and-reel format compatible with automated assembly.

• Tape Width: 8mm.
• Reel Size: Standard 7-inch diameter.
• Quantity per Reel: 5000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Packing Standard: Conforms to ANSI/EIA-481 specifications. Empty pockets in the tape are sealed with a cover tape.

8. Application Suggestions

8.1 Typical Application Scenarios

• Status Indicators: Power, connectivity, or function status lights in consumer electronics, appliances, and networking equipment.
• Backlighting: Edge-lighting for LCD displays, keypad illumination in mobile devices and remote controls.
• Decorative Lighting: Accent lighting in automotive interiors, signage, and decorative fixtures.
• Sensor Systems: As a light source for optical sensors.

8.2 Design Considerations

• Current Limiting: Always use a series current-limiting resistor or a constant-current driver circuit. Do not connect directly to a voltage source.
• Thermal Management: Although power dissipation is low, ensure adequate PCB copper area or thermal vias under the solder pads if operating at high ambient temperatures or near maximum current, to keep the junction temperature within safe limits.
• Optical Design: The water-clear lens produces a focused beam. For diffused or wider area lighting, external diffusers or light guides may be necessary.
• Binning Selection: For applications requiring uniform color and brightness (e.g., multi-LED arrays), specify the required bin codes (V_F, I_V, λ_d) to your supplier.

9. Technical Comparison & Differentiation

The primary differentiating factor of the LTST-C281TBKT-5A is its ultra-low 0.35mm profile. Compared to standard chip LEDs which are often 0.6mm or taller, this device enables thinner end products. The use of InGaN technology provides higher efficiency and brighter blue output compared to older technologies. Its compatibility with standard IR reflow and tape-and-reel packaging makes it a drop-in solution for automated, high-volume manufacturing lines without requiring special processes.

10. Frequently Asked Questions (FAQ)

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

A: Peak Wavelength (λ_P) is the physical wavelength where the LED emits the most optical power. Dominant Wavelength (λ_d) is a calculated value that represents the single monochromatic color that would appear to the human eye to match the LED's color. λ_d is often more relevant for color-based applications.

Q: Can I drive this LED at 20mA continuously?

A: Yes, 20mA is the maximum recommended DC forward current. For optimal longevity and to account for temperature effects, driving it at a lower current such as 10-15mA is often a good practice if the required brightness is achieved.

Q: Why is there a binning system?

A> Semiconductor manufacturing has natural variations. Binning sorts LEDs into groups with tightly controlled characteristics (voltage, brightness, color), allowing designers to use consistent components and manufacturers to sell parts with guaranteed performance ranges.

Q: Is a heat sink required?

A: For most applications at or below the typical 5mA drive current, no dedicated heat sink is needed due to the low power dissipation (76mW max). However, thermal management through the PCB should be considered for high-current or high-ambient-temperature operation.

11. Practical Design Case Study

Scenario: Designing a low-profile status indicator for a wearable fitness tracker.

Requirements: Thickness < 0.5mm, blue color, visible in daylight, powered by a 3.3V system rail.

Solution: The LTST-C281TBKT-5A's 0.35mm height perfectly fits the mechanical constraint. Selecting a bin code from the AD (470-475nm) wavelength bin ensures the desired blue color. To drive it from 3.3V, a series resistor is calculated. Assuming a typical V_F of 2.9V (from Bin 3) and a target I_F of 5mA: R = (3.3V - 2.9V) / 0.005A = 80Ω. A standard 82Ω resistor would be used. At 5mA, the luminous intensity will be between 11.2 and 45.0 mcd (depending on the I_V bin), which is sufficient for a status indicator. The device's compatibility with reflow soldering allows it to be assembled alongside other SMD components on the tracker's main PCB.

12. Technology Principle Introduction

The LTST-C281TBKT-5A is based on InGaN (Indium Gallium Nitride) semiconductor technology. When a forward voltage is applied across the p-n junction of this material, electrons and holes recombine, releasing energy in the form of photons (light). The specific ratio of indium to gallium in the crystal lattice determines the bandgap energy, which in turn dictates the wavelength (color) of the emitted light. For this LED, the composition is tuned to emit in the blue region of the spectrum (~470nm). The water-clear epoxy lens encapsulates and protects the semiconductor die while allowing the light to exit with minimal absorption or scattering.

13. Industry Trends

The trend in SMD LEDs continues toward higher efficiency (more light output per watt of electrical input), smaller package sizes, and lower profiles to enable thinner consumer electronics. There is also a strong drive for improved color consistency and tighter binning tolerances to meet the demands of high-quality display backlighting and architectural lighting. The move to lead-free (Pb-free) soldering and RoHS compliance, which this device supports, is now a global industry standard. Future developments may include integrated driver circuitry within the LED package and enhanced reliability for operation in harsher environments.