SMD LED LTST-C193KSKT-5A Datasheet - Dimensions 1.6x0.8x0.35mm - Voltage 1.7-2.3V - Power 50mW - Yellow - English Technical Document

1. Product Overview

This document details the specifications for the LTST-C193KSKT-5A, a surface-mount device (SMD) LED lamp. This component belongs to a family of miniature LEDs designed specifically for automated printed circuit board (PCB) assembly processes and applications where space is a critical constraint. The compact form factor and reliable performance make it suitable for integration into a wide array of modern electronic equipment.

1.1 Features and Core Advantages

The LTST-C193KSKT-5A offers several key technological advantages that enhance its usability and performance in demanding applications.

• RoHS Compliance: The device is manufactured to meet the Restriction of Hazardous Substances directive, ensuring it is free from specific hazardous materials like lead, mercury, and cadmium.
• Ultra-Thin Profile: With a height of only 0.35 mm, this is an extra-thin chip LED, enabling its use in extremely slim consumer electronics and displays.
• High-Brightness AlInGaP Chip: Utilizes an Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material, which is known for producing high-efficiency light in the yellow, orange, and red spectral regions with good stability.
• Industry-Standard Packaging: Supplied in 8mm tape on 7-inch diameter reels, compatible with standard automated pick-and-place equipment used in high-volume electronics manufacturing.
• Process Compatibility: Designed to be compatible with infrared (IR) reflow soldering processes, which is the standard for assembling surface-mount components. It is also I.C. (Integrated Circuit) compatible in terms of driving characteristics.

1.2 Target Market and Applications

The combination of small size, brightness, and reliability opens up numerous application possibilities across various sectors.

• Telecommunications: Status indicators in cordless phones, cellular phones, and network equipment.
• Computing and Office Automation: Backlighting for keypads and keyboards in notebook computers, and status indicators on various peripherals.
• Consumer Electronics and Home Appliances: Power, mode, or function indicators in audio/video equipment, kitchen appliances, and other household devices.
• Industrial Equipment: Panel indicators for machinery and control systems.
• Display Technology: Suitable for microdisplays and as a luminous source for symbols and signal indicators.

2. Technical Parameters: In-Depth Objective Interpretation

This section provides a detailed breakdown of the electrical, optical, and environmental limits and characteristics of the LED.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation at or beyond these limits is not advised. All ratings are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): 50 mW. This is the maximum amount of power the LED package can dissipate as heat.
• Continuous Forward Current (IF): 20 mA DC. The maximum steady-state current that can be applied.
• Peak Forward Current: 40 mA, permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to briefly achieve higher light output.
• Reverse Voltage (VR): 5 V. Exceeding this voltage in reverse bias can cause junction breakdown.
• 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.
• Infrared Soldering Condition: Withstands a peak temperature of 260°C for a maximum of 10 seconds during reflow soldering.

2.2 Electro-Optical Characteristics

These are the typical performance parameters measured under specific test conditions (Ta=25°C, IF=5 mA unless noted).

• Luminous Intensity (Iv): Ranges from 7.1 to 45.0 millicandelas (mcd). This wide range is managed through a binning system (see Section 3). Intensity is measured using a sensor filtered to match the human eye's photopic response (CIE curve).
• Viewing Angle (2θ1/2): 130 degrees. This is the full angle at which the luminous intensity drops to half of its value measured on-axis, indicating a very wide viewing pattern.
• Peak Emission Wavelength (λP): 591.0 nm. The wavelength at the highest point in the LED's spectral output curve.
• Dominant Wavelength (λd): 587.0 - 594.5 nm. This is the single wavelength perceived by the human eye that defines the color (yellow). It is derived from the CIE chromaticity coordinates.
• Spectral Line Half-Width (Δλ): 15 nm. A measure of the spectral purity; a smaller value indicates a more monochromatic light source.
• Forward Voltage (VF): 1.7 - 2.3 V at 5 mA. The voltage drop across the LED when operating.
• Reverse Current (IR): 10 μA maximum when a 5V reverse bias is applied.

2.3 Thermal Considerations

While not explicitly detailed in thermal resistance (θJA) terms, the maximum power dissipation of 50 mW and the operating temperature range define the thermal operating window. Proper PCB layout, including adequate copper area for the attachment pads, is crucial for heat dissipation, especially when operating near the maximum current rating. Exceeding the maximum junction temperature will accelerate light output degradation and reduce operational lifetime.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins. The LTST-C193KSKT-5A uses a three-dimensional binning system for forward voltage, luminous intensity, and dominant wavelength (hue).

3.1 Forward Voltage (VF) Binning

Bins ensure LEDs in a circuit have similar voltage drops, promoting uniform brightness when connected in parallel. Tolerance per bin is ±0.1V.
Bin E2: 1.7V - 1.9V
Bin E3: 1.9V - 2.1V
Bin E4: 2.1V - 2.3V

3.2 Luminous Intensity (Iv) Binning

This groups LEDs by their light output at a standard test current (5mA). Tolerance per bin is ±15%.
Bin K: 7.1 - 11.2 mcd
Bin L: 11.2 - 18.0 mcd
Bin M: 18.0 - 28.0 mcd
Bin N: 28.0 - 45.0 mcd

3.3 Hue / Dominant Wavelength (λd) Binning

Critical for color-critical applications, this binning ensures a consistent shade of yellow. Tolerance per bin is ±1 nm.
Bin J: 587.0 - 589.5 nm
Bin K: 589.5 - 592.0 nm
Bin L: 592.0 - 594.5 nm

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet, their implications are described here.

4.1 Current vs. Voltage (I-V) Characteristic

The forward voltage (VF) has a positive temperature coefficient and increases with current. The typical VF range of 1.7-2.3V at 5mA must be considered when designing the current-limiting circuitry. Driving the LED at its maximum DC current of 20 mA will result in a higher forward voltage, necessitating a corresponding adjustment in the supply or driver design.

4.2 Temperature Dependence

Like all semiconductors, LED performance is temperature-sensitive. The luminous intensity of AlInGaP LEDs typically decreases as the junction temperature increases. Therefore, maintaining a low thermal resistance path from the LED junction to the ambient environment is key to achieving stable, long-term brightness. The specified operating temperature range of -30°C to +85°C defines the environmental limits for this relationship.

4.3 Spectral Distribution

The LED emits in a narrow band centered around 591 nm (peak) with a half-width of 15 nm, defining its yellow color. The dominant wavelength (λd) is the parameter used for hue binning. The spectrum is largely invariant with current, but the peak wavelength may shift slightly with temperature.

5. Mechanical and Package Information

5.1 Package Dimensions

The LED has a compact chip-scale style package. Key dimensions (in millimeters) are approximately 1.6mm in length, 0.8mm in width, and a very low profile height of 0.35mm. Detailed mechanical drawings should be consulted for exact tolerances (±0.1mm typically) and features like the cathode identification mark.

5.2 Recommended PCB Attachment Pad Layout

A suggested land pattern (footprint) for the PCB is provided to ensure reliable soldering and mechanical stability. This pattern typically includes pads slightly larger than the device terminals to facilitate good solder fillet formation. Adhering to this recommendation helps prevent tombstoning (component standing up on one end) during reflow.

5.3 Polarity Identification

The device has an anode and cathode. The datasheet indicates the method for identifying the cathode, which is essential for correct orientation during assembly and circuit operation. Incorrect polarity will prevent the LED from illuminating and applying reverse voltage beyond 5V may damage it.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Parameters

The device is rated for infrared (IR) reflow soldering with a peak temperature of 260°C for a maximum of 10 seconds. A suggested reflow profile is provided, typically following JEDEC standards. It includes:
- Pre-heat: 150-200°C for up to 120 seconds to gradually heat the board and activate flux.
- Reflow (Liquidus): Peak temperature not exceeding 260°C, with time above 260°C kept to a minimum.
- Cooling: Controlled cool-down period.
The profile must be characterized for the specific PCB assembly, considering board thickness, component density, and solder paste type.

6.2 Hand Soldering

If manual repair is necessary, use a soldering iron with a temperature not exceeding 300°C. The contact time with the LED terminal should be limited to a maximum of 3 seconds for a single operation to prevent thermal damage to the plastic package and the semiconductor die.

6.3 Storage and Handling Conditions

- Moisture Sensitivity Level (MSL): The device is rated MSL 2a. Once the original moisture-proof bag is opened, the components must be subjected to IR reflow soldering within 672 hours (28 days) under factory floor conditions (≤30°C/60% RH).
- Extended Storage: For storage beyond 672 hours out of the original bag, components should be stored in a dry cabinet or sealed container with desiccant.
- Baking: Components exceeding the floor life should be baked at approximately 60°C for at least 20 hours prior to soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.
- ESD Precautions: The LED is sensitive to electrostatic discharge (ESD). Handle using appropriate ESD controls such as grounded wrist straps, anti-static mats, and conductive containers.

6.4 Cleaning

If post-solder cleaning is required, use only specified solvents. Immersing the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute is acceptable. Avoid unspecified or aggressive chemical cleaners that may damage the epoxy lens or package.

7. Packaging and Ordering Information

7.1 Standard Packaging

The product is supplied in industry-standard embossed carrier tape for automated handling. The tape width is 8mm. This tape is wound onto 7-inch (178mm) diameter reels.

7.2 Reel Specifications and Quantity

Each full 7-inch reel contains 5000 pieces of the LTST-C193KSKT-5A LED. The tape has a cover tape to protect components during shipping and handling. The packaging conforms to ANSI/EIA-481 specifications.

7.3 Minimum Order Quantity and Part Number

The standard part number is LTST-C193KSKT-5A. The suffix \"-5A\" may indicate specific bin combinations or other product variations. For non-full-reel orders, a minimum packing quantity of 500 pieces is typically available for remainder quantities.

8. Application Suggestions and Design Considerations

8.1 Current Limiting

An LED is a current-driven device. Always use a series current-limiting resistor or a constant-current driver circuit to set the operating current. The resistor value can be calculated using Ohm's Law: R = (V_supply - VF_LED) / I_desired. Choose a resistor power rating suitable for the dissipation. For example, to drive the LED at 5mA from a 3.3V supply with a typical VF of 2.0V: R = (3.3V - 2.0V) / 0.005A = 260Ω. A 270Ω standard value resistor would be appropriate.

8.2 Thermal Management in Design

For applications running at high currents (e.g., near 20mA) or in high ambient temperatures, thermal management is crucial. Use the recommended PCB pad layout and connect the thermal pads to a sufficient area of copper pour to act as a heat sink. This helps conduct heat away from the LED junction, maintaining brightness and longevity.

8.3 Optical Design

The 130-degree viewing angle provides a very wide emission pattern, ideal for status indicators meant to be seen from various angles. For applications requiring a more directed beam, secondary optics (such as a lens mounted over the LED) would be necessary. The water-clear lens of this LED is suitable for use with light guides or diffusers in backlighting applications.

9. Technical Comparison and Differentiation

The primary differentiating factors of the LTST-C193KSKT-5A are its ultra-thin 0.35mm height and its use of AlInGaP technology for yellow emission.

• vs. Standard SMD LEDs (e.g., 0603, 0402): This chip LED is significantly thinner, enabling design in space-constrained products where even a standard 0.6mm-tall LED is too large.
• vs. Other Yellow LED Technologies: Compared to older Yellow Gallium Phosphide (GaP) LEDs, AlInGaP offers substantially higher luminous efficiency and better temperature stability, resulting in brighter and more consistent light output.
• vs. White LEDs: For applications requiring pure yellow indication (e.g., specific warning symbols), a monochromatic yellow AlInGaP LED is more efficient and color-saturated than a phosphor-converted white LED with a yellow filter.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED directly from a 3.3V or 5V microcontroller pin?
A: No. You must always use a series current-limiting resistor. Connecting it directly would attempt to draw excessive current, likely damaging both the LED and the microcontroller output pin.

Q: Why is there such a wide range in Luminous Intensity (7.1 to 45.0 mcd)?
A> This is the total production spread. Through the binning process (K, L, M, N bins), you can select LEDs with a much tighter intensity range for your application to ensure uniform brightness.

Q: What is the difference between Peak Wavelength and Dominant Wavelength?
A: Peak Wavelength (λP) is the physical peak of the light spectrum emitted. Dominant Wavelength (λd) is a calculated value based on color perception; it's the single wavelength that matches the color the human eye sees. λd is more relevant for color specification and binning.

Q: How many times can I reflow solder this LED?
A: The datasheet specifies the soldering process can be performed a maximum of two times, with peak temperature not exceeding 260°C for 10 seconds each time. Multiple reflows increase thermal stress.

11. Practical Use Case Examples

Case 1: Ultra-Thin Tablet Keyboard Backlighting: A designer is creating a detachable keyboard for a tablet. The height budget for components under the keycaps is extremely limited. The 0.35mm profile of the LTST-C193KSKT-5A allows it to fit where a standard LED cannot. Several LEDs are placed on a flexible PCB under translucent keycaps. They are driven at 5-10mA via a constant-current driver IC to provide even, low-power backlighting. The wide viewing angle ensures light spreads well under each key.

Case 2: Industrial Sensor Status Indicator: A compact industrial proximity sensor needs a bright, reliable status LED to indicate power and detection state. The AlInGaP yellow LED provides high brightness for good visibility in well-lit environments. The designer uses LEDs from the high-intensity \"N\" bin and drives them at 15mA through a current-limiting resistor from the sensor's 24V supply (using a transistor as a switch). The robust SMD package withstands the vibration and temperature variations typical in an industrial setting.

12. Technology Introduction and Operating Principle

Light Emitting Diodes (LEDs) are semiconductor devices that emit light through a process called electroluminescence. The core of the LTST-C193KSKT-5A is a chip made from Aluminum Indium Gallium Phosphide (AlInGaP). This III-V compound semiconductor material has a direct bandgap suitable for efficient light emission.

Operating Principle: When a forward voltage exceeding the diode's junction potential (VF) is applied, electrons from the n-type semiconductor and holes from the p-type semiconductor are injected into the active region. When these charge carriers (electrons and holes) recombine, they release energy. In an AlInGaP LED, this energy is released primarily as photons (light) in the yellow/orange/red part of the spectrum. The specific wavelength (color) is determined by the bandgap energy of the semiconductor material, which is engineered by adjusting the ratios of Aluminum, Indium, Gallium, and Phosphorus during crystal growth. The generated light escapes through the epoxy lens, which also provides environmental protection.

13. Industry Trends and Developments

The market for SMD LEDs like the LTST-C193KSKT-5A continues to evolve driven by several key trends:

• Miniaturization: The demand for thinner and smaller LEDs is relentless, driven by consumer electronics (smartphones, wearables, ultra-thin laptops). Chip-scale packages (CSP) and even thinner variants are areas of ongoing development.
• Increased Efficiency: Improvements in epitaxial growth, chip design, and light extraction techniques continue to push the luminous efficacy (lumens per watt) of colored LEDs like AlInGaP higher, allowing for brighter light or lower power consumption.
• High-Reliability Demands: As LEDs are used in more critical applications (automotive interiors, medical devices), there is a focus on enhancing long-term reliability, color stability over temperature and time, and performance under harsh conditions.
• Integration: There is a trend towards integrating multiple LED chips (e.g., RGB for color mixing) into a single package or combining the LED with driver ICs and control logic for \"smart LED\" modules.
• Advanced Packaging: New packaging materials and methods are being developed to better manage heat from increasingly powerful miniature LEDs and to provide more precise optical control directly from the package.