SMD LED LTST-C950RTBKT Specification - Package 3.2x2.8x1.9mm - Voltage 2.8-3.8V - Power 76mW - Blue InGaN Chip - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a surface-mount device (SMD) LED lamp. Designed for automated printed circuit board (PCB) assembly, this component is suitable for space-constrained applications across a wide range of electronic equipment.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Incorporates a dome lens design for optimized light distribution.
• Utilizes an ultra-bright Indium Gallium Nitride (InGaN) semiconductor chip.
• Packaged in 8mm tape on 7-inch diameter reels for automated handling.
• Conforms to EIA (Electronic Industries Alliance) standard package dimensions.
• IC (Integrated Circuit) compatible drive characteristics.
• Fully compatible with standard automatic pick-and-place assembly equipment.
• Designed to withstand infrared (IR) reflow soldering processes.

1.2 Target Applications

This LED is engineered for use in diverse sectors requiring reliable, compact indicators or backlighting solutions.

• Telecommunications & Office Automation: Status indicators in routers, modems, printers, and copiers.
• Consumer & Home Appliances: Power, mode, or function indicators.
• Industrial Equipment: Machine status, fault, or operational mode signaling.
• Keypad/Keyboard Backlighting: Illumination for low-light environments.
• Status Indicators: Power-on, battery charging, network activity.
• Micro-Displays & Symbol Luminaires: Small-scale informational displays and icon lighting.

2. Technical Parameters: In-Depth Objective Interpretation

The following section details the critical electrical, optical, and thermal parameters that define the component's performance envelope. All measurements are standardized at an ambient temperature (Ta) of 25°C unless otherwise specified.

2.1 Absolute Maximum Ratings

These values represent the stress limits beyond which permanent damage to the device may occur. Continuous operation at or near these limits is not advised and will reduce reliability and lifetime.

• Power Dissipation (Pd): 76 mW. This is the maximum total power the package can dissipate as heat, calculated from forward voltage (Vf) and current (If).
• Peak Forward Current (Ifp): 100 mA. Permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to prevent overheating.
• Continuous DC Forward Current (If): 20 mA. The recommended maximum current for reliable continuous operation.
• Operating Temperature Range: -20°C to +80°C. The ambient temperature range over which the device is specified to function correctly.
• Storage Temperature Range: -30°C to +100°C. The safe temperature range for the device when not powered.
• Infrared Reflow Soldering Condition: 260°C peak temperature for a maximum of 10 seconds. This defines the thermal profile the component can withstand during PCB assembly.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters under standard test conditions.

• Luminous Intensity (Iv): 450 - 2800 mcd (millicandela) at If=20mA. This wide range is managed through a binning system (see Section 3). Measurement uses a filter approximating the CIE photopic eye-response curve.
• Viewing Angle (2θ½): 25 degrees. This is the full angle at which the luminous intensity drops to half of its peak (axial) value, defining the beam width.
• Peak Emission Wavelength (λp): 468 nm (typical). The wavelength at which the spectral power output is highest.
• Dominant Wavelength (λd): 460 - 475 nm at If=20mA. This is the single wavelength perceived by the human eye, derived from the CIE chromaticity diagram. It is also binned.
• Spectral Line Half-Width (Δλ): 25 nm (typical). The spectral bandwidth measured at half the maximum intensity, indicating color purity.
• Forward Voltage (Vf): 2.8 - 3.8 V at If=20mA. The voltage drop across the LED when operating. This parameter is binned.
• Reverse Current (Ir): 10 μA (maximum) at Vr=5V. LEDs are not designed for reverse bias operation; this parameter is for test purposes only.

2.3 Thermal Considerations

While not explicitly graphed in the provided data, thermal management is implicit in the ratings. Exceeding the maximum junction temperature, inferred from the Power Dissipation and thermal resistance of the package, will accelerate lumen depreciation and can lead to catastrophic failure. The specified operating temperature range of -20°C to +80°C is the ambient temperature; the junction temperature will be higher based on driving current and PCB layout.

3. Binning System Explanation

Due to inherent variations in semiconductor manufacturing, LEDs are sorted (binned) post-production based on key parameters. This system allows designers to select components that meet specific consistency requirements for their application.

3.1 Forward Voltage (Vf) Binning

Units are sorted by their forward voltage drop at 20mA. This is critical for designing current-limiting circuits and ensuring uniform brightness in multi-LED arrays powered by a constant voltage source.

• Bin Codes: D7 (2.80-3.00V), D8 (3.00-3.20V), D9 (3.20-3.40V), D10 (3.40-3.60V), D11 (3.60-3.80V).
• Tolerance: +/- 0.1V within each bin.

3.2 Luminous Intensity (Iv) Binning

This is the primary brightness sorting parameter, measured in millicandelas (mcd) at 20mA.

• Bin Codes: U (450-710 mcd), V (710-1120 mcd), W (1120-1800 mcd), X (1800-2800 mcd).
• Tolerance: +/- 15% within each bin.

3.3 Hue (Dominant Wavelength, λd) Binning

This binning ensures color consistency, which is vital for applications where multiple LEDs are viewed together.

• Bin Codes: AB (460.0-465.0 nm), AC (465.0-470.0 nm), AD (470.0-475.0 nm).
• Tolerance: +/- 1 nm within each bin.

A complete part number for ordering would typically include codes for Vf, Iv, and λd bins to guarantee specific performance characteristics.

4. Performance Curve Analysis

Graphical data provides insight into device behavior under varying conditions. The following analysis is based on typical curves expected for an InGaN blue LED.

4.1 Current vs. Voltage (I-V) Characteristic

The I-V curve is non-linear, exhibiting a sharp turn-on at the forward voltage (Vf). Above this knee voltage, the current increases exponentially with a small increase in voltage. This underscores the necessity of driving LEDs with a current-limited source (e.g., a constant current driver or a voltage source with a series resistor) rather than a pure voltage source, to prevent thermal runaway.

4.2 Luminous Intensity vs. Forward Current (Iv-If)

This curve shows that luminous intensity is approximately proportional to forward current in the typical operating range (e.g., up to 20mA). However, efficiency (lumens per watt) may peak at a current lower than the maximum rating. Driving above the recommended current leads to increased heat, reduced efficiency, and accelerated degradation.

4.3 Temperature Dependence

While not explicitly shown, it is a fundamental characteristic that LED performance is temperature-sensitive.

• Forward Voltage (Vf): Decreases with increasing junction temperature (negative temperature coefficient). This can affect the stability of simple resistor-based current limiting circuits.
• Luminous Intensity (Iv): Decreases with increasing junction temperature. High-temperature operation will result in reduced light output.
• Wavelength (λd): Typically shifts slightly with temperature, which can be a consideration in color-critical applications.

4.4 Spectral Distribution

The spectral output graph would show a single, dominant peak in the blue region (~468 nm) with a characteristic full width at half maximum (FWHM) of about 25 nm. There is minimal emission in other parts of the visible spectrum, which is typical for a monochromatic InGaN LED.

5. Mechanical & Package Information

5.1 Package Dimensions

The device conforms to a standard SMD footprint. Key dimensions (in millimeters) include a typical body size of approximately 3.2mm (L) x 2.8mm (W) x 1.9mm (H), with a tolerance of ±0.1mm unless otherwise noted. The specific land pattern (footprint) is provided for PCB design.

5.2 Polarity Identification

The cathode is typically indicated by a visual marker on the package, such as a notch, a green dot, or a cut corner on the lens. The PCB footprint should include a corresponding marker. Incorrect polarity connection will prevent the LED from illuminating and, if a reverse voltage exceeding the maximum rating is applied, may damage the device.

5.3 Tape and Reel Specifications

The component is supplied in embossed carrier tape for automated assembly.

• Tape Width: 8 mm.
• Reel Diameter: 7 inches.
• Quantity per Reel: 2000 pieces.
• Pocket Sealing: Empty pockets are sealed with cover tape.
• Packaging Standard: Complies with ANSI/EIA-481 specifications.

6. Soldering & Assembly Guidelines

6.1 Recommended IR Reflow Profile (Pb-Free Process)

A JEDEC-standard compliant reflow profile is recommended for reliable soldering.

• Preheat Temperature: 150-200°C.
• Preheat Time: Maximum 120 seconds to allow for uniform heating and paste activation.
• Peak Temperature: Maximum 260°C.
• Time Above Liquidus (TAL): The sample profile suggests a target of 10 seconds maximum at peak temperature.
• Maximum Reflow Cycles: Two times recommended.

Note: The optimal profile depends on the specific PCB design, solder paste, and oven. The provided values are guidelines; board-level characterization is advised.

6.2 Hand Soldering (If Required)

Use with extreme caution to avoid thermal shock.

• Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per pad.
• Maximum Cycles: One time only.

6.3 Cleaning

If cleaning after soldering is necessary, use only approved solvents to avoid damaging the epoxy lens.

• Recommended Solvents: Ethyl alcohol or isopropyl alcohol.
• Process: Immerse at normal temperature for less than one minute. Do not use ultrasonic cleaning unless verified to be safe for the component.
• Avoid: Unspecified or aggressive chemical cleaners.

7. Storage & Handling

7.1 Electrostatic Discharge (ESD) Precautions

This device is sensitive to electrostatic discharge. Proper ESD controls must be in place during handling and assembly.

• Use grounded wrist straps or anti-static gloves.
• Ensure all workstations, tools, and equipment are properly grounded.
• Store and transport in conductive or anti-static packaging.

7.2 Moisture Sensitivity & Storage

The package is moisture-sensitive (likely MSL 3).

• Sealed Package: Store at ≤30°C and ≤90% RH. Use within one year from the dry-pack date.
• Opened Package: For components removed from the original moisture barrier bag, the storage ambient should not exceed 30°C / 60% RH.
• Floor Life: It is recommended to complete IR reflow within one week after opening the dry pack.
• Extended Storage (Out of Bag): Store in a sealed container with desiccant or in a nitrogen desiccator.
• Rebaking: If exposed for more than one week, bake at approximately 60°C for at least 20 hours before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

8. Application Notes & Design Considerations

8.1 Current Limiting

Always use a current-limiting mechanism. The simplest method is a series resistor calculated as R = (Vsupply - Vf) / If, where Vf should be the maximum value from the bin or datasheet to ensure current does not exceed the limit under worst-case conditions. For better stability and efficiency across temperature and unit-to-unit Vf variations, consider using a constant current driver.

8.2 Thermal Management on PCB

Although a small device, power dissipation (up to 76mW) generates heat.

• Use the recommended PCB pad layout to facilitate heat transfer from the LED's thermal pad (if present) to the copper on the board.
• Incorporate thermal vias under the pad to conduct heat to inner or bottom board layers.
• Avoid placing the LED near other heat-generating components.
• For high-current or high-ambient-temperature applications, derate the maximum forward current to keep the junction temperature within safe limits.

8.3 Optical Design

The 25-degree viewing angle provides a relatively focused beam. For wider illumination, secondary optics (e.g., diffusers, light guides) will be required. The water-clear lens is suitable for applications where the blue chip color is desired; for a diffused appearance, a milky-white or colored diffuser lens would need to be added externally.

9. Frequently Asked Questions (Based on Technical Parameters)

9.1 What is the difference between Peak Wavelength and Dominant Wavelength?

Peak Wavelength (λp) is the literal peak of the spectral power distribution curve (468 nm). Dominant Wavelength (λd) is the single wavelength perceived by the human eye, calculated from the CIE color coordinates, and may differ slightly from λp (460-475 nm). λd is more relevant for color specification.

9.2 Can I drive this LED at 30mA for more brightness?

No. The Absolute Maximum Rating for continuous DC forward current is 20 mA. Exceeding this rating will increase junction temperature beyond design limits, leading to rapid lumen depreciation, color shift, and potential catastrophic failure. For higher light output, select an LED bin with higher luminous intensity or a product rated for a higher current.

9.3 Why is the Forward Voltage range so wide (2.8-3.8V)?

This is a characteristic of semiconductor manufacturing variation. The binning system (D7 to D11) exists precisely to manage this. For consistent performance in an array, specify and use LEDs from the same Vf bin, or use a constant current driver which inherently compensates for Vf differences.

9.4 Is this LED suitable for automotive or medical applications?

The datasheet states the LED is intended for ordinary electronic equipment. For applications requiring exceptional reliability or where failure could jeopardize safety (automotive, medical, aviation), consultation with the manufacturer is required to obtain components qualified and tested to the relevant industry standards (e.g., AEC-Q102 for automotive).

10. Technology Introduction & Trends

10.1 InGaN Chip Technology

This LED utilizes an Indium Gallium Nitride (InGaN) semiconductor chip. InGaN is the material system that enables efficient emission in the blue, green, and white (via phosphor conversion) regions of the spectrum. Its development was pivotal for creating white LEDs and full-color displays. The technology offers high efficiency, good reliability, and the ability to produce very bright devices from small chip areas.

10.2 Industry Trends

The general trend in SMD LEDs is toward:

• Higher Efficiency (lm/W): Reducing energy consumption for the same light output.
• Improved Color Consistency: Tighter binning tolerances for applications like display backlighting.
• Higher Reliability & Lifetime: Especially for demanding applications like automotive lighting.
• Miniaturization: Continued reduction in package size (e.g., 0201, 01005 metrics) for ultra-compact devices.
• Integrated Solutions: LEDs with built-in current limiting resistors, Zener diodes for ESD protection, or multi-chip packages for color mixing.

This component represents a mature, well-established product category optimized for reliable performance in high-volume, automated assembly environments.