SMD LED Chip LTST-C190KSKT Datasheet - 0.80mm Height - 1.8-2.4V Forward Voltage - 45-180mcd Luminous Intensity - Yellow Color - English Technical Document

1. Product Overview

This document details the specifications for a miniature, surface-mount LED lamp designed for automated printed circuit board assembly and space-constrained applications. The device utilizes an ultra-bright AlInGaP semiconductor chip to produce yellow light, encapsulated in a water-clear lens package. Its primary design goals are high luminous efficiency, compatibility with modern manufacturing processes, and reliability in a wide range of operating environments.

1.1 Features

• Compliant with RoHS environmental directives.
• Extremely low profile with a height of only 0.80 millimeters.
• High-brightness output enabled by AlInGaP chip technology.
• Packaged on 8mm tape wound onto 7-inch diameter reels for automated pick-and-place.
• Standardized EIA package outline for design compatibility.
• Logic-level compatible drive requirements.
• Designed for compatibility with automated placement equipment.
• Suitable for infrared (IR) reflow soldering processes.

1.2 Target Applications

This LED is suitable for a broad spectrum of electronic equipment where compact size, high brightness, and reliable performance are required. Key application areas include:

• Telecommunication devices (e.g., cellular phones, cordless phones).
• Office automation equipment (e.g., notebook computers, network systems).
• Home appliances and consumer electronics.
• Industrial control and instrumentation panels.
• Keypad, keyboard, and button backlighting.
• Status and power indicators.
• Micro-displays and icon illumination.
• Signal and symbolic luminaires.

2. Technical Parameters: In-Depth Analysis

The following section provides a detailed, objective interpretation of the device's key electrical, optical, and thermal characteristics. All data is specified at an ambient temperature (Ta) of 25°C unless otherwise noted.

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 and should be avoided for reliable long-term performance.

• Power Dissipation (Pd): 75 mW. This is the maximum amount of power the package can dissipate as heat.
• Peak Forward Current (I_FP): 80 mA. This is permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to prevent overheating.
• Continuous Forward Current (I_F): 30 mA DC. This is the recommended maximum current for continuous operation.
• Reverse Voltage (V_R): 5 V. Exceeding this voltage in reverse bias can cause junction breakdown.
• Operating Temperature Range: -30°C to +85°C. The device is guaranteed to function within this ambient temperature range.
• Storage Temperature Range: -40°C to +85°C.
• Infrared Soldering Condition: Withstands 260°C peak temperature for 10 seconds, which is standard for lead-free (Pb-free) solder reflow processes.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters under standard test conditions.

• Luminous Intensity (I_V): 45.0 to 180.0 millicandelas (mcd) at I_F = 20mA. Measured using a sensor filtered to match the CIE standard photopic eye-response curve. The wide range is managed through a binning system.
• Viewing Angle (2θ_1/2): 130 degrees. This is the full angle at which the luminous intensity drops to half of its on-axis (0°) value, indicating a very wide emission pattern suitable for area illumination.
• Peak Emission Wavelength (λ_P): 588.0 nm (nominal). This is the wavelength at which the spectral power output is highest.
• Dominant Wavelength (λ_d): 584.5 to 597.0 nm at I_F = 20mA. This is the single wavelength perceived by the human eye to define the color (yellow). It is derived from the CIE chromaticity coordinates.
• Spectral Line Half-Width (Δλ): Approximately 15 nm. This indicates the spectral purity; a narrower width means a more saturated, pure color.
• Forward Voltage (V_F): 1.8 to 2.4 Volts at I_F = 20mA. The voltage drop across the LED when conducting current.
• Reverse Current (I_R): 10 μA maximum at V_R = 5V. A small leakage current when the device is reverse-biased.

3. Binning System Explanation

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

3.1 Forward Voltage (V_F) Binning

For Yellow color, tested at 20mA.

• Bin F2: V_F = 1.80V to 2.10V.
• Bin F3: V_F = 2.10V to 2.40V.
• Tolerance per bin: ±0.1 Volt.

3.2 Luminous Intensity (I_V) Binning

For Yellow color, tested at 20mA.

• Bin P: 45.0 to 71.0 mcd.
• Bin Q: 71.0 to 112.0 mcd.
• Bin R: 112.0 to 180.0 mcd.
• Tolerance per bin: ±15%.

3.3 Hue (Dominant Wavelength) Binning

For Yellow color, tested at 20mA.

• Bin H: λ_d = 584.5 to 587.0 nm.
• Bin J: λ_d = 587.0 to 589.5 nm.
• Bin K: λ_d = 589.5 to 592.0 nm.
• Bin L: λ_d = 592.0 to 594.5 nm.
• Bin M: λ_d = 594.5 to 597.0 nm.
• Tolerance per bin: ±1 nm.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet, their implications are critical for design.

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

The I-V characteristic is exponential. The typical V_F range of 1.8-2.4V at 20mA must be considered when designing current-limiting circuitry. A constant current source is highly recommended over a simple series resistor for stable light output, especially over temperature variations.

4.2 Luminous Intensity vs. Forward Current

Light output is generally proportional to forward current within the rated limits. However, efficiency may drop at very high currents due to increased heat. Operating at or below the typical 20mA test condition is advised for optimal efficiency and longevity.

4.3 Spectral Distribution

The spectral output curve centers around 588 nm (yellow) with a typical half-width of 15 nm. This relatively narrow bandwidth ensures good color saturation. The dominant wavelength (λ_d) is the parameter used for color binning, as it correlates directly with human color perception.

4.4 Temperature Dependence

LED performance is temperature-sensitive. Typically, forward voltage (V_F) has a negative temperature coefficient (decreases with rising temperature), while luminous intensity decreases with rising junction temperature. Proper thermal management on the PCB is essential to maintain consistent brightness and color over the operating life.

5. Mechanical & Package Information

5.1 Package Dimensions

The device features an industry-standard chip LED footprint. Key dimensions include a body height of 0.80 mm (max), making it suitable for ultra-thin applications. All dimensional tolerances are ±0.1 mm unless otherwise specified. The package material is designed to withstand the thermal stress of IR reflow soldering.

5.2 Recommended PCB Land Pattern

A suggested solder pad layout is provided to ensure reliable soldering and proper alignment. The design accommodates the formation of a good solder fillet while preventing solder bridging between the anode and cathode terminals. Adhering to this recommendation is crucial for achieving high yield in automated assembly.

5.3 Polarity Identification

The cathode terminal is typically marked, often by a notch, a green marking, or a different pad size/shape on the tape and reel packaging. Correct polarity orientation during placement is mandatory for the device to function.

6. Soldering & Assembly Guidelines

6.1 IR Reflow Soldering Profile (Pb-Free)

The device is qualified for lead-free soldering processes. A recommended reflow profile is provided, adhering to JEDEC standards.

• Pre-heat: 150°C to 200°C.
• Pre-heat Time: Maximum 120 seconds.
• Peak Temperature: Maximum 260°C.
• Time Above Liquidus (at peak): Maximum 10 seconds. The device can withstand a maximum of two reflow cycles under these conditions.

Note: The optimal profile depends on the specific PCB design, solder paste, and oven. The provided profile serves as a generic target, and process characterization is recommended.

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 lead.
• Hand soldering should be limited to one-time repair only, not for mass production.

6.3 Storage & Handling

• ESD Precautions: LEDs are sensitive to electrostatic discharge (ESD). Use wrist straps, grounded workstations, and anti-static packaging.
• Moisture Sensitivity Level (MSL): The device is rated MSL 3. Once the original moisture-proof bag is opened, components must be IR-reflowed within one week (168 hours) of factory floor conditions (≤ 30°C/60% RH).
• Extended Storage (Opened Bag): For storage beyond one week, components must be stored in a sealed container with desiccant or in a nitrogen environment. If stored beyond the floor life, a bake at 60°C for at least 20 hours is required before soldering.

6.4 Cleaning

If post-solder cleaning is required, use only approved solvents. Recommended agents include ethyl alcohol or isopropyl alcohol at room temperature. Immersion time should be less than one minute. Avoid unspecified chemical cleaners that may damage the epoxy lens or package.

7. Packaging & Ordering Information

7.1 Tape and Reel Specifications

The components are supplied on embossed carrier tape for automated assembly.

• Tape Width: 8 mm.
• Reel Diameter: 7 inches (178 mm).
• Quantity per Reel: 4000 pieces (standard full reel).
• Minimum Pack Quantity: 500 pieces for remainder reels.
• Cover Tape: Empty pockets are sealed with top cover tape.
• Missing Components: A maximum of two consecutive missing lamps is allowed per specification.
• Standard: Packaging conforms to ANSI/EIA-481 specifications.

8. Application Design Considerations

8.1 Current Limiting

Always use a current-limiting resistor or, preferably, a constant current driver in series with the LED. The resistor value can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet (2.4V) to ensure the current does not exceed the desired level even with a low-V_F part.

8.2 Thermal Management

Although power dissipation is low (75 mW max), heat can still affect performance and lifespan. Ensure the PCB has adequate copper area connected to the LED's thermal pads (if any) or nearby ground plane to act as a heat sink. Avoid placing the LED near other heat-generating components.

8.3 Optical Design

The 130-degree viewing angle provides very wide, diffuse illumination. For applications requiring a more focused beam, secondary optics (e.g., lenses, light pipes) will be necessary. The water-clear lens is optimal for maintaining color purity and maximum light output.

9. Technical Comparison & Differentiation

This device offers several key advantages in its category:

• Profile: At 0.80mm height, it is among the thinnest chip LEDs, enabling design in modern, slim devices.
• Brightness: The use of AlInGaP technology provides higher luminous efficiency compared to traditional GaAsP or GaP LEDs, resulting in higher mcd output at the same current.
• Color: AlInGaP produces a more saturated and stable yellow color with better performance over temperature compared to older technologies.
• Process Compatibility: Full compatibility with high-volume, automated SMT assembly and Pb-free IR reflow soldering reduces manufacturing complexity and cost.

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 the CIE color chart that represents the single wavelength the human eye perceives the color to be. For design, λ_d is more relevant for color matching.

10.2 Can I drive this LED at 30mA continuously?

Yes, 30mA is the maximum rated continuous DC forward current. However, for optimal longevity and to account for potential thermal rise in the application, driving it at or below the test condition of 20mA is a common and conservative practice.

10.3 Why is binning important?

Binning ensures color and brightness consistency within a production batch and across multiple batches. For applications where uniform appearance is critical (e.g., backlighting an array of LEDs), specifying tight bins for V_F, I_V, and λ_d is essential.

10.4 How do I interpret the MSL 3 rating?

MSL 3 means the package can absorb a damaging amount of moisture from the ambient air. Once the sealed bag is opened, you have 168 hours (1 week) under ≤ 30°C/60% RH conditions to complete the solder reflow process. If this time is exceeded, the parts must be baked to remove moisture before soldering to prevent \"popcorning\" or package cracking during reflow.

11. Design-in Use Case Example

Scenario: Status Indicator on a Portable Medical Device

A designer needs a low-power, highly reliable yellow status LED for a battery-operated handheld monitor. The space is extremely limited, and the device must pass medical reliability standards.

• Part Selection: The LTST-C190KSKT is chosen for its 0.80mm height, RoHS compliance, and proven reliability.
• Circuit Design: The LED is driven by a GPIO pin of a microcontroller through a 100Ω series resistor (assuming a 3.3V supply: (3.3V - 2.1V_typ) / 0.020A ≈ 60Ω, using 100Ω for margin). The current is limited to ~12-15mA, well below the 30mA maximum, to conserve battery life and ensure ultra-long lifespan.
• PCB Layout: The recommended land pattern is used. A small thermal relief connection to a ground plane is added to aid heat dissipation without making soldering difficult.
• Procurement: The designer specifies bins Q or R for luminous intensity to ensure the indicator is clearly visible, and bin J or K for dominant wavelength to get a consistent, standard yellow hue across all production units.
• Assembly: The LEDs are kept in their sealed bag until the production line is ready. The PCB assembly uses a controlled, JEDEC-compliant reflow profile to ensure solder joint reliability without damaging the LED.

12. Technology Principle Introduction

This LED is based on Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor technology. When a forward voltage is applied across the p-n junction, electrons and holes recombine in the active region, releasing energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly corresponds to the wavelength (color) of the emitted light—in this case, yellow (~588 nm). AlInGaP is known for its high internal quantum efficiency, leading to superior brightness and color stability compared to older material systems like Gallium Arsenide Phosphide (GaAsP). The chip is then encapsulated in an epoxy resin package that shapes the light output and provides mechanical and environmental protection.

13. Industry Trends

The surface-mount LED market continues to evolve with several clear trends:

• Miniaturization: Demand for thinner and smaller packages (like this 0.80mm height chip) is driven by consumer electronics striving for sleeker designs.
• Increased Efficiency: Ongoing material science improvements aim to extract more lumens per watt (efficacy), reducing power consumption for the same light output.
• Higher Reliability & Stability: Advancements in packaging materials and chip design focus on maintaining color point and luminous flux over extended lifetimes and under harsh environmental conditions.
• Broadened Color Gamut: While this part is monochromatic yellow, the industry is also advancing phosphor-converted and multi-chip solutions to achieve precise white points and saturated colors for display backlighting and general lighting.
• Integration: There is a growing trend towards integrating drive electronics, protection components, and multiple LED chips into single, smarter \"LED modules\" to simplify end-product design.