SMD LED LTST-C171KEKT Datasheet - Dimensions 3.2x1.6x0.8mm - Forward Voltage 2.4V - Power 75mW - Red Color - English Technical Document

1. Product Overview

The LTST-C171KEKT is a surface-mount device (SMD) light-emitting diode (LED) belonging to the chip LED category. Its primary defining characteristic is an ultra-low profile, with a package height of only 0.8 millimeters. This makes it suitable for applications where space constraints, particularly vertical clearance (Z-height), are critical. The device utilizes an Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material as the light source, which is engineered to produce high-efficiency red light emission. The LED is supplied in a standard EIA-compatible package format, mounted on 8mm carrier tape and wound onto 7-inch diameter reels, facilitating compatibility with high-speed automated pick-and-place assembly equipment used in modern electronics manufacturing.

2. Technical Parameter Deep-Dive

2.1 Absolute Maximum Ratings

The absolute maximum ratings define the stress limits beyond which permanent damage to the device may occur. These are not conditions for normal operation. For the LTST-C171KEKT, the maximum continuous forward current (DC) is specified as 30 mA at an ambient temperature (Ta) of 25°C. The device can handle higher transient currents under pulsed conditions, with a peak forward current of 80 mA permissible at a 1/10 duty cycle and a 0.1ms pulse width. The maximum power dissipation is 75 mW. A critical thermal parameter is the derating factor for forward current, which is linear from 50°C onwards at a rate of 0.4 mA per °C. This means the allowable continuous current must be reduced as the operating temperature increases above 50°C to prevent overheating. The maximum reverse voltage that can be applied without causing breakdown is 5 V. The device is rated for operation and storage within a temperature range of -55°C to +85°C.

2.2 Electrical & Optical Characteristics

The typical operating characteristics are measured at Ta=25°C. The key optical parameter, luminous intensity (Iv), has a typical value of 54.0 millicandelas (mcd) when driven at the test condition of 20 mA forward current (IF). It is important to note that this measurement uses a sensor and filter calibrated to the CIE photopic eye-response curve. The viewing angle, defined as 2θ1/2 where the intensity drops to half its on-axis value, is a wide 130 degrees, indicating a broad, diffuse emission pattern rather than a narrow beam. The spectral characteristics show a peak emission wavelength (λP) typically at 632 nm, while the dominant wavelength (λd), which perceptually defines the color, is typically 624 nm. The spectral line half-width (Δλ) is 20 nm, describing the spread of the emitted wavelengths. Electrically, the forward voltage (VF) at 20 mA is typically 2.4 V, with a maximum of 2.4 V. The reverse current (IR) is very low, with a maximum of 10 μA at the full 5 V reverse bias. The device capacitance (C) is typically 40 pF measured at zero bias and 1 MHz.

3. Binning System Explanation

The product utilizes a binning system to categorize units based on their measured luminous intensity. This ensures consistency within a production batch for applications requiring uniform brightness. The bin codes for the LTST-C171KEKT are defined as follows: Bin Code M covers intensities from 18.0 to 28.0 mcd, N from 28.0 to 45.0 mcd, P from 45.0 to 71.0 mcd, Q from 71.0 to 112.0 mcd, and R from 112.0 to 180.0 mcd, all measured at IF=20mA. A tolerance of +/-15% is applied to the limits of each intensity bin. The datasheet does not indicate separate binning for dominant wavelength or forward voltage for this specific part number, suggesting tight control on these parameters or a single-bin offering.

4. Performance Curve Analysis

While the provided text excerpt references typical characteristic curves on page 6, the specific graphs are not included in the text. Based on standard LED behavior, one would expect to see curves illustrating the relationship between forward current (IF) and luminous intensity (Iv), which is generally linear in the normal operating range. Another crucial curve would depict the forward voltage (VF) versus forward current (IF), showing the diode's exponential I-V characteristic. Temperature dependence curves are also standard, showing how luminous intensity and forward voltage change with ambient or junction temperature, typically showing a decrease in intensity and a slight decrease in VF as temperature rises. A relative spectral power distribution curve would visually represent the emission peak at ~632 nm and the 20 nm half-width.

5. Mechanical & Packaging Information

The LED is packaged in an industry-standard chip LED footprint. The key mechanical feature is the ultra-thin 0.80 mm height. Detailed package dimension drawings are referenced, specifying the length, width, lead spacing, and other critical mechanical tolerances, which are typically ±0.10 mm. The device is designed for tape-and-reel packaging compatible with automated assembly. The reel specifications follow ANSI/EIA 481-1-A-1994 standards. A 7-inch diameter reel contains 3000 pieces. The tape has pockets sealed with a cover tape. Guidelines specify a maximum of two consecutive missing components (empty pockets) and a minimum packing quantity of 500 pieces for remainder reels. Suggested soldering pad layout dimensions are also provided to ensure proper solder joint formation and mechanical stability during and after the reflow process.

6. Soldering & Assembly Guidelines

The device is compatible with both infrared (IR) and vapor phase reflow soldering processes, which is essential for lead-free (Pb-free) assembly. Specific soldering condition limits are provided. For wave soldering, a peak temperature of 260°C for a maximum of 5 seconds is specified. For infrared reflow, the same 260°C peak for 5 seconds is allowed. For vapor phase reflow, the condition is 215°C for up to 3 minutes. The datasheet includes suggested reflow temperature profiles for both normal (tin-lead) and Pb-free processes. The Pb-free profile recommendation explicitly states it is for use with SnAgCu (Tin-Silver-Copper) solder paste. Additional general soldering recommendations are listed in the cautions section, including pre-heat parameters and maximum soldering iron temperature (300°C for 3 seconds maximum, one time only).

7. Application Recommendations

This LED is designed for general-purpose electronic equipment applications, such as office equipment, communication devices, and household appliances. A critical design consideration is that LEDs are current-operated devices. To ensure uniform brightness when driving multiple LEDs in parallel, it is strongly recommended to use a current-limiting resistor in series with each individual LED (Circuit Model A). Driving multiple LEDs in parallel directly from a voltage source without individual resistors (Circuit Model B) is discouraged, as slight variations in the forward voltage (Vf) characteristics between individual LEDs can cause significant differences in current share and, consequently, perceived brightness. The wide 130-degree viewing angle makes it suitable for status indicators, backlighting icons, or general illumination where broad angular coverage is desired.

8. Handling, Storage & Cautions

Comprehensive handling instructions are provided to ensure reliability. For storage, the ambient should not exceed 30°C and 60% relative humidity. If LEDs are removed from their original moisture-barrier packaging, it is recommended to complete the IR reflow soldering process within 672 hours (28 days). For longer storage outside the original bag, storage in a sealed container with desiccant or in a nitrogen atmosphere is advised. If storage exceeds 672 hours, 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. For cleaning, only alcohol-based solvents like isopropyl alcohol or ethyl alcohol should be used at room temperature for less than one minute. Unspecified chemicals may damage the package. Robust Electrostatic Discharge (ESD) precautions are mandatory, as the device is sensitive. Recommendations include using grounded wrist straps, grounding all equipment and work surfaces, and employing ionizers to neutralize static charge. ESD damage can manifest as high reverse leakage current, low forward voltage, or failure to illuminate at low currents.

9. Technical Comparison & Differentiation

The primary differentiating factor of the LTST-C171KEKT is its 0.8 mm profile, which is exceptionally low for a chip LED. Compared to standard 1.0 mm or 1.2 mm high chip LEDs, this enables design in thinner end products. The use of AlInGaP technology provides high luminous efficiency for red light, typically offering better performance and stability than older technologies like GaAsP. The wide 130-degree viewing angle is another key feature, providing a very broad and even light emission compared to LEDs with narrower viewing angles, which are more suitable for focused beam applications. Its compatibility with standard IR/vapor phase reflow and tape-and-reel packaging makes it a drop-in component for high-volume automated surface-mount technology (SMT) lines.

10. Frequently Asked Questions (FAQ)

Q: What is the main advantage of the 0.8mm height?
A: It allows for integration into extremely thin electronic devices, such as modern smartphones, tablets, ultra-thin laptops, and wearable technology, where internal space is at a premium.

Q: Can I drive this LED directly from a 3.3V or 5V logic supply?
A: No. An LED must be driven with a current-limited source. Connecting it directly to a voltage source will cause excessive current to flow, destroying the device. Always use a series resistor or a constant-current driver circuit.

Q: Why is a series resistor needed for each LED in parallel?
A: The forward voltage (Vf) of LEDs has a manufacturing tolerance. Without individual resistors, LEDs with a slightly lower Vf will draw disproportionately more current, becoming brighter and potentially overheating, while those with a higher Vf will be dimmer. The resistor helps equalize the current.

Q: Is this LED suitable for outdoor applications?
A: The operating temperature range is -55°C to +85°C, which covers most outdoor conditions. However, long-term reliability in outdoor environments also depends on factors like UV exposure and humidity sealing of the final product assembly, which are not specified for the component alone.

Q: What does \"Water Clear\" lens mean?
A: It indicates the lens material is transparent and colorless. This allows the native color of the AlInGaP chip (red) to be emitted without any tinting or diffusion from the lens itself, resulting in a saturated color.

11. Design and Usage Case Study

Scenario: Designing a status indicator panel for a slim network router.
The design requires multiple red status LEDs (for power, internet, Wi-Fi, etc.) to be placed on a front panel with limited depth behind the fascia. Using traditional 1.2mm high LEDs would force a thicker product enclosure or a complex stepped PCB design. By selecting the LTST-C171KEKT with its 0.8mm height, the PCB can be placed closer to the front panel, saving 0.4mm of vertical space per LED location. This allows for a sleeker, more compact router design. The wide 130-degree viewing angle ensures the indicator lights are clearly visible from a wide range of viewing positions in a room. The designer implements Circuit Model A, using a single current-limiting resistor for each LED connected in parallel to a 3.3V rail on the board's microcontroller, ensuring all indicators have uniform brightness. The PCB layout follows the suggested soldering pad dimensions from the datasheet to guarantee reliable solder joints during the lead-free reflow process specified for the main board assembly.

12. Operating Principle

Light emission in this LED is based on the principle of electroluminescence in a semiconductor p-n junction. The active region is composed of Aluminum Indium Gallium Phosphide (AlInGaP), a direct bandgap semiconductor material. When a forward bias voltage exceeding the material's bandgap energy is applied, electrons are injected from the n-type region and holes from the p-type region into the active region. These charge carriers recombine radiatively; that is, when an electron recombines with a hole, it releases energy in the form of a photon. The wavelength (color) of the emitted photon is determined by the bandgap energy of the AlInGaP material, which is engineered to produce photons in the red portion of the visible spectrum (around 624-632 nm). The \"water clear\" epoxy lens encapsulates the semiconductor chip, providing mechanical protection, shaping the light output beam (resulting in the 130-degree viewing angle), and enhancing light extraction from the chip.

13. Technology Trends

The development of ultra-thin chip LEDs like the LTST-C171KEKT is driven by the ongoing trend towards miniaturization and thickness reduction in consumer electronics, automotive interiors, and wearable devices. The move to AlInGaP from older materials like GaAsP offers higher efficiency, meaning more light output (lumens) per unit of electrical input power (watts), contributing to better energy efficiency in end products. In manufacturing, compatibility with lead-free (Pb-free) high-temperature reflow profiles is now a standard requirement due to global environmental regulations (e.g., RoHS). The industry continues to push for higher brightness in smaller packages, improved color consistency through tighter binning, and enhanced reliability under harsh conditions like high temperature and humidity. Furthermore, integration of multiple LED chips (RGB) into a single ultra-thin package for full-color applications is an area of active development.