SMD LED LTST-C283KRKT-5A Datasheet - 2.0x1.25x0.2mm - Red 631nm - 30mA - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a surface-mount device (SMD) LED lamp. This component is designed for automated printed circuit board (PCB) assembly, featuring a miniature form factor ideal for space-constrained applications. Its primary function is to serve as a highly efficient light source for indication, backlighting, and signaling purposes.

1.1 Core Advantages and Target Markets

The device offers several key advantages that make it suitable for modern electronics manufacturing. It is compliant with RoHS (Restriction of Hazardous Substances) directives. The package is extra thin, measuring only 0.2 mm in height, enabling use in ultra-slim products. It utilizes an AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material, which is known for producing high luminous efficiency in the red color spectrum. The component is packaged in industry-standard 8mm tape on 7-inch reels, making it fully compatible with high-speed automated pick-and-place equipment. It is also designed to withstand standard infrared (IR) reflow soldering processes used in surface-mount technology (SMT) assembly lines.

The target applications are broad, encompassing telecommunications equipment (e.g., cordless and cellular phones), office automation devices (e.g., notebook computers, network systems), home appliances, and industrial equipment. Specific uses include keypad or keyboard backlighting, status indicators, micro-displays, and various signal or symbol luminary applications.

2. Technical Parameters: In-Depth Objective Interpretation

This section details the absolute limits and standard operating characteristics of the device. All parameters are specified at an ambient temperature (Ta) of 25°C unless stated otherwise.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Continuous operation under these conditions is not advised.

• Power Dissipation (Pd): 75 mW. This is the maximum amount of power the device can dissipate as heat.
• Peak Forward Current (I_F(PEAK)): 80 mA. This is the maximum allowable instantaneous forward current, typically specified under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to manage thermal load.
• DC Forward Current (I_F): 30 mA. This is the maximum recommended continuous forward current for reliable long-term operation.
• Operating Temperature Range: -30°C to +85°C. The ambient temperature range over which the device is designed to function.
• Storage Temperature Range: -40°C to +85°C. The temperature range for non-operational storage.
• Infrared Soldering Condition: 260°C for 10 seconds. The maximum thermal profile the package can withstand during reflow soldering for lead-free processes.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured under standard test conditions.

• Luminous Intensity (I_V): 4.5 - 45.0 mcd (millicandela) at I_F = 5mA. This wide range is managed through a binning system (see Section 3). Intensity is measured using a sensor filtered to match the CIE standard human eye photopic response curve.
• Viewing Angle (2θ_1/2): 130 degrees. This is the full angle at which the luminous intensity is half the value measured on the central axis (0°). A wide viewing angle indicates a more diffuse light emission pattern.
• Peak Emission Wavelength (λ_P): 639 nm (typical). This is the wavelength at which the spectral power distribution of the emitted light reaches its maximum.
• Dominant Wavelength (λ_d): 631 nm (typical) at I_F = 5mA. This is the single wavelength perceived by the human eye that defines the color of the light. It is derived from the CIE chromaticity coordinates.
• Spectral Line Half-Width (Δλ): 20 nm (typical). This is the spectral bandwidth measured at half the maximum intensity (Full Width at Half Maximum - FWHM).
• Forward Voltage (V_F): 1.70 - 2.3 V at I_F = 5mA. The voltage drop across the LED when operating. This range is also managed through binning.
• Reverse Current (I_R): 10 μA (maximum) at V_R = 5V. The small leakage current that flows when a reverse voltage is applied.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins based on key parameters. This allows designers to select components that meet specific application requirements for brightness and voltage.

3.1 Forward Voltage (V_F) Binning

For the red color variant, forward voltage is categorized into three bins when measured at a test current of 5mA. The tolerance within each bin is ±0.1V.

• Bin Code E2: V_F range from 1.70V to 1.90V.
• Bin Code E3: V_F range from 1.90V to 2.10V.
• Bin Code E4: V_F range from 2.10V to 2.30V.

3.2 Luminous Intensity (I_V) Binning

Luminous intensity is categorized into five bins, also measured at I_F = 5mA. The tolerance on each bin is ±15%.

• Bin Code J: 4.50 - 7.10 mcd
• Bin Code K: 7.10 - 11.20 mcd
• Bin Code L: 11.20 - 18.00 mcd
• Bin Code M: 18.00 - 28.00 mcd
• Bin Code N: 28.00 - 45.00 mcd

This binning allows for precise selection based on required brightness levels, which is critical for applications like backlighting where uniformity is important.

4. Performance Curve Analysis

Typical performance curves provide visual insight into the device's behavior under varying conditions. These curves are essential for circuit design and thermal management.

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

The I-V characteristic is non-linear, typical of a diode. The curve shows the relationship between the forward voltage (V_F) and the forward current (I_F). Designers use this to determine the necessary driving voltage for a desired operating current, which directly correlates to light output. The curve will shift with temperature.

4.2 Luminous Intensity vs. Forward Current

This curve demonstrates that luminous intensity is approximately proportional to the forward current over a significant range. However, efficiency may drop at very high currents due to increased junction temperature and other effects. Operating within the recommended DC current range ensures optimal performance and longevity.

4.3 Spectral Distribution

The spectral distribution curve plots relative intensity against wavelength. It confirms the peak emission wavelength (~639 nm) and the spectral half-width (~20 nm), defining the pure red color output of this AlInGaP chip.

5. Mechanical and Package Information

5.1 Package Dimensions

The device conforms to an industry-standard SMD package outline. Key dimensions include a length of 2.0 mm, a width of 1.25 mm, and a height of 0.2 mm (ultra-thin profile). Detailed mechanical drawings specify all critical dimensions, including pad locations and tolerances, which are typically ±0.1 mm. The lens is water clear.

5.2 Recommended PCB Attachment Pad Layout

A land pattern design is provided for PCB layout. This pattern ensures proper solder joint formation during reflow, provides adequate thermal relief, and maintains mechanical stability. Adhering to this recommended footprint is crucial for successful assembly and reliability.

5.3 Polarity Identification

The component has a marked cathode (negative terminal). The datasheet illustrates how this marking appears on the device body (typically a notch, green dot, or other indicator on the cathode side). Correct polarity orientation during placement is essential for the circuit to function.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Conditions

For lead-free solder processes, a specific reflow profile is recommended. Key parameters include a pre-heat temperature between 150-200°C, a pre-heat time up to 120 seconds maximum, a peak body temperature not exceeding 260°C, and a time above 260°C limited to 10 seconds maximum. The device should not be subjected to more than two reflow cycles. These limits are based on JEDEC standards to prevent package cracking or degradation of internal materials.

6.2 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 soldering time limited to 3 seconds per joint. Hand soldering should be performed only once.

6.3 Cleaning

If post-solder cleaning is required, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute is acceptable. Unspecified chemical cleaners may damage the plastic package or lens.

6.4 Storage Conditions

LEDs are sensitive to moisture. When stored in their original sealed moisture-proof bag with desiccant, they should be kept at 30°C or less and 90% relative humidity (RH) or less, with a recommended use-within period of one year. Once the original packaging is opened, the storage ambient should not exceed 30°C or 60% RH. Components removed from their original packaging should ideally be reflow-soldered within one week (Moisture Sensitivity Level 3, MSL 3). For longer storage outside the original bag, they should be kept in a sealed container with desiccant. If stored for more than one week, a bake-out at approximately 60°C for at least 20 hours is recommended before assembly to remove absorbed moisture and prevent \"popcorning\" during reflow.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The components are supplied in embossed carrier tape with a protective cover tape. The tape width is 8 mm. Reels have a standard diameter of 7 inches (178 mm). Each reel contains 5000 pieces. For quantities less than a full reel, a minimum packing quantity of 500 pieces applies for remainder lots. The packaging conforms to ANSI/EIA-481 specifications.

8. Application Suggestions

8.1 Typical Application Circuits

An LED is a current-driven device. To ensure consistent brightness, especially when multiple LEDs are used in parallel, a current-limiting mechanism is essential. The simplest method is to use a series resistor. The resistor value (R_series) can be calculated using Ohm's Law: R_series = (V_supply - V_F) / I_F. For more precise and efficient control, constant current drivers or integrated LED driver ICs are recommended. This prevents current hogging in parallel strings and ensures uniform light output across all devices, compensating for natural variations in V_F.

8.2 Design Considerations

• Thermal Management: Although power dissipation is low, maintaining the junction temperature within limits is key to long-term reliability and stable light output. Ensure adequate PCB copper area or thermal vias under the LED pads to conduct heat away, especially when operating near maximum current.
• ESD Protection: LEDs are susceptible to damage from electrostatic discharge (ESD). Proper ESD handling procedures must be followed during assembly, including the use of grounded workstations, wrist straps, and conductive containers.
• Optical Design: The wide 130-degree viewing angle provides a diffuse light pattern. For applications requiring a more focused beam, secondary optics (lenses or light guides) may be necessary.

9. Technical Comparison and Differentiation

This AlInGaP-based red LED offers distinct advantages compared to older technologies like GaAsP (Gallium Arsenide Phosphide). The primary differentiator is significantly higher luminous efficiency, meaning it produces more light (millicandelas) for the same input current (mA). This results in lower power consumption for a given brightness level or much higher brightness within the same power budget. The ultra-thin 0.2mm profile is a key mechanical advantage over many standard SMD LEDs, enabling design in increasingly slim consumer electronics.

10. Frequently Asked Questions (Based on Technical Parameters)

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

Peak Wavelength (λ_P) is the physical wavelength where the LED emits the most optical power. Dominant Wavelength (λ_d) is a calculated value based on human color perception (CIE chart) that best represents the perceived color. For monochromatic LEDs like this red one, they are often close but not identical. Designers concerned with color points (e.g., in displays) should reference the dominant wavelength.

10.2 Why is a current-limiting resistor necessary?

An LED's forward voltage has a negative temperature coefficient and can vary from unit to unit (as seen in the binning). If connected directly to a voltage source, a small change in V_F can cause a large, potentially destructive, change in current. A series resistor (or constant current source) provides negative feedback, stabilizing the operating current against these variations.

10.3 Can I drive this LED with a voltage higher than its V_F?

Yes, but you must always include a series current-limiting element (resistor or active circuit). The driving voltage must be higher than the LED's V_F to allow current to flow, but the excess voltage is dropped across the current-limiting component to set the correct I_F.

11. Practical Use Case Example

Scenario: Designing a status indicator panel for a network router. The panel requires five red status LEDs. Uniform brightness is critical for user experience. Design Steps: 1) Determine required brightness: Select Bin L (11.2-18.0 mcd) for clear visibility. 2) Determine drive current: Choose I_F = 5mA (standard test condition) for long life and low heat. 3) Calculate series resistor: Assuming a 3.3V supply and a typical V_F of 2.0V (from Bin E3), R = (3.3V - 2.0V) / 0.005A = 260Ω. Use the nearest standard value (270Ω). 4) Layout: Use the recommended PCB pad layout. Connect all five LEDs in parallel, each with its own 270Ω resistor to the 3.3V rail. This ensures individual current control for uniformity. 5) Assembly: Follow the MSL-3 guidelines and the specified reflow profile.

12. Operating 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 region and holes from the p-type region are injected into the junction region. When these charge carriers recombine, they release energy. In this specific device, the semiconductor material is AlInGaP, engineered so that this released energy is in the form of photons (light) in the red portion of the visible spectrum (around 631-639 nm). The specific composition of the aluminum, indium, gallium, and phosphide atoms determines the bandgap energy, and thus the color of the emitted light.

13. Technology Trends

The general trend in SMD LED technology continues toward higher efficiency (more lumens per watt), smaller package sizes, and higher reliability. For indicator-type LEDs, the focus is on achieving brighter output at lower currents and developing ever-thinner profiles to meet the demands of miniaturized portable electronics. Advancements in materials science, such as improved epitaxial growth techniques for AlInGaP and other compound semiconductors, directly contribute to these performance gains. Furthermore, standardization of packages and assembly processes ensures compatibility with evolving high-volume, automated manufacturing lines.