SMD LED LTST-C170KDKT Datasheet - Red AllnGaP - 130° Viewing Angle - 2.8-28mcd @10mA - 1.6-2.4V - 50mW - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTST-C170KDKT, a surface-mount device (SMD) LED lamp. This component belongs to a family of LEDs designed for automated printed circuit board (PCB) assembly, offering a compact form factor ideal for space-constrained applications. The LED utilizes an Ultra Bright Aluminum Indium Gallium Phosphide (AllnGaP) semiconductor chip to produce red light, encapsulated in a water-clear lens package. Its design prioritizes compatibility with modern high-volume manufacturing processes.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• High-brightness output enabled by an AllnGaP chip technology.
• Packaged on 8mm tape wound onto 7-inch diameter reels for automated pick-and-place equipment.
• Standard EIA (Electronic Industries Alliance) package footprint.
• Input compatible with standard integrated circuit (IC) logic levels.
• Designed for use with automatic component placement systems.
• Withstands infrared (IR) reflow soldering processes, essential for lead-free (Pb-free) assembly.

1.2 Target Applications

The LTST-C170KDKT is suitable for a broad spectrum of electronic devices where reliable, compact status indication or backlighting is required. Key application areas include:

• Telecommunications Equipment: Status indicators in cordless phones, cellular phones, and network system hardware.
• Computing Devices: Backlighting for keypads and keyboards in notebook computers and other portable electronics.
• Consumer & Industrial Electronics: Indicator lights in home appliances, office automation equipment, and industrial control systems.
• Display & Signage: Micro-displays and low-level illumination for indoor signal or symbol luminaires.

2. Technical Parameters: In-Depth Objective Interpretation

The performance of the LED is defined by a set of absolute maximum ratings and standard operating characteristics. Understanding these parameters is critical for reliable circuit design and ensuring long-term device performance.

2.1 Absolute Maximum Ratings

These values represent the stress limits beyond which permanent damage to the LED may occur. Operation under these conditions is not guaranteed. All ratings are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): 50 mW. The maximum total power the device can dissipate as heat.
• Peak Forward Current (I_FP): 40 mA. This is the maximum allowable instantaneous forward current, typically specified under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to prevent overheating.
• Continuous Forward Current (I_F): 20 mA. The maximum DC current that can be applied continuously.
• Reverse Voltage (V_R): 5 V. Applying a reverse voltage exceeding this value 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 parameters define the typical performance of the LED under standard test conditions (Ta=25°C, I_F=10mA unless noted).

• Luminous Intensity (I_V): 2.8 - 28.0 mcd (millicandela). This is the perceived brightness of the light output as measured by a sensor filtered to match the human eye's photopic response (CIE curve). The wide range indicates a binning system is used (see Section 3).
• Viewing Angle (2θ_1/2): 130 degrees. This is the full angle at which the luminous intensity drops to half of its value measured on-axis (0°). A 130° angle indicates a wide, diffuse emission pattern suitable for broad area illumination.
• Peak Emission Wavelength (λ_P): 650 nm (typical). The wavelength at which the spectral power output is maximum.
• Dominant Wavelength (λ_d): 630 - 645 nm. This is the single wavelength perceived by the human eye that defines the color (red) of the LED, derived from the CIE chromaticity coordinates.
• Spectral Line Half-Width (Δλ): 20 nm (typical). The bandwidth of the emitted spectrum measured at half the maximum intensity (Full Width at Half Maximum - FWHM).
• Forward Voltage (V_F): 1.6 - 2.4 V. The voltage drop across the LED when driven with 10mA. This range accounts for normal manufacturing variance in the semiconductor junction.
• Reverse Current (I_R): 10 μA (max). The small leakage current that flows when the maximum reverse voltage (5V) is applied.

2.3 Thermal Considerations

While not explicitly detailed in a separate thermal resistance parameter, the power dissipation (50mW) and operating temperature range (-30°C to +85°C) are the primary thermal constraints. Exceeding the maximum junction temperature, which is indirectly limited by these ratings, will reduce luminous output and lifespan. Adequate PCB layout for heat dissipation is recommended for applications operating near maximum current.

3. Binning System Explanation

To ensure consistency in brightness for end products, LEDs are sorted (binned) based on their measured luminous intensity. The LTST-C170KDKT uses the following bin code system for its red output.

3.1 Luminous Intensity (I_V) Binning

The luminous intensity is measured at a forward current of 10mA. The bins are defined as follows, with a tolerance of ±15% within each bin.

• Bin H: 2.8 mcd (Min) to 4.5 mcd (Max)
• Bin J: 4.5 mcd to 7.1 mcd
• Bin K: 7.1 mcd to 11.2 mcd
• Bin L: 11.2 mcd to 18.0 mcd
• Bin M: 18.0 mcd to 28.0 mcd

This system allows designers to select the appropriate brightness grade for their application, balancing cost and performance. For example, a high-brightness indicator might require Bin M, while a less critical status light could use Bin H or J.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Figure 1 for spectral output, Figure 5 for viewing angle pattern), their general implications are described below based on standard LED behavior and the provided parameters.

4.1 Current vs. Voltage (I-V) Characteristic

The forward voltage (V_F) range of 1.6V to 2.4V at 10mA is typical for a red AllnGaP LED. The I-V curve is exponential, like a standard diode. Below the threshold voltage (around 1.4-1.5V for this material), very little current flows. Above this threshold, current increases rapidly with a small increase in voltage. This is why LEDs must be driven with a current-limiting mechanism (resistor or constant-current source) and not directly with a voltage source.

4.2 Luminous Intensity vs. Forward Current

The light output (luminous intensity) is approximately proportional to the forward current over a significant range. Driving the LED at its maximum continuous current (20mA) would typically produce roughly double the luminous intensity measured at the standard test condition of 10mA, though efficiency may slightly decrease at higher currents due to heating.

4.3 Temperature Dependence

LED performance is temperature-sensitive. As the junction temperature increases:

1. Forward Voltage (V_F): Decreases. This has a negative temperature coefficient.
2. Luminous Intensity (I_V): Decreases. Higher temperatures reduce the internal quantum efficiency of the semiconductor, leading to lower light output for the same drive current.
3. Dominant Wavelength (λ_d): May shift slightly, typically to longer wavelengths (red-shift) with increasing temperature.

These effects underscore the importance of thermal management in high-reliability or high-brightness applications.

4.4 Spectral Distribution

The spectral output is characterized by a peak wavelength of 650nm and a dominant wavelength between 630-645nm. The spectral half-width of 20nm indicates a relatively pure, saturated red color compared to broader-spectrum light sources like incandescent bulbs. The narrow bandwidth is a characteristic of direct-bandgap semiconductor emitters like AllnGaP.

5. Mechanical and Package Information

5.1 Package Dimensions

The LED conforms to a standard EIA SMD package outline. All critical dimensions for PCB footprint design and component placement are provided in the datasheet drawings, with a standard tolerance of ±0.1mm unless otherwise specified. The package features a water-clear lens, which does not diffuse the light, resulting in the chip's inherent wide 130° viewing angle pattern.

5.2 Recommended PCB Pad Layout

A suggested land pattern (solder pad geometry) for the PCB is provided to ensure proper solder joint formation during reflow. Adhering to this recommendation promotes good solder wetting, mechanical strength, and proper alignment of the component. The pad design accounts for the necessary solder fillet and prevents tombstoning (component standing up on one end during reflow).

5.3 Polarity Identification

The datasheet includes markings or diagrams indicating the anode and cathode terminals. Correct polarity is essential for operation. Applying reverse bias beyond the 5V rating can cause immediate failure.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Parameters

The LED is qualified for lead-free (Pb-free) soldering processes. The key parameters are:

• Pre-heat Temperature: 150°C to 200°C.
• Pre-heat Time: Maximum 120 seconds to gradually heat the assembly and activate the solder paste flux.
• Peak Reflow Temperature: Maximum 260°C. The component can withstand this temperature for a limited time.
• Time Above Liquidus (at peak temperature): Maximum 10 seconds. The device should not be subjected to the peak temperature for longer than this duration. A maximum of two reflow cycles is permitted.

These parameters align with common JEDEC industry profiles. The actual temperature profile must be characterized for the specific PCB assembly, considering board thickness, number of layers, and other components.

6.2 Hand Soldering (If Necessary)

If manual repair is required:

• Soldering Iron Temperature: Maximum 300°C.
• Contact Time: Maximum 3 seconds per joint.
• Limit: Only one hand-soldering cycle is allowed per joint to minimize thermal stress on the package.

6.3 Cleaning

If post-solder cleaning is required, only specified solvents should be used to avoid damaging the plastic package. Recommended agents include ethyl alcohol or isopropyl alcohol at room temperature. The LED should be immersed for less than one minute. Unspecified chemical cleaners must be avoided.

6.4 Storage and Handling

• ESD (Electrostatic Discharge) Precautions: The LED is sensitive to static electricity. Handling should be performed using anti-static measures such as wrist straps, grounded workstations, and conductive foam.
• Moisture Sensitivity Level (MSL): The device is rated MSL 2a. This means that once the original moisture-proof barrier bag is opened, the components must be soldered within 672 hours (28 days) under factory floor conditions (<30°C / 60% RH).
• Extended Storage (Out of Bag): For storage beyond 672 hours, components should be kept in a sealed container with desiccant or in a nitrogen atmosphere. If exposed beyond the limit, a bake-out at approximately 60°C for at least 20 hours is required before soldering to remove absorbed moisture and prevent \"popcorning\" (package cracking during reflow).
• Original Packaging Storage: Unopened reels should be stored at 30°C or less and 90% relative humidity or less, with a recommended shelf life of one year from the date code.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied in industry-standard embossed carrier tape for automated assembly.

• Tape Width: 8 mm.
• Reel Diameter: 7 inches.
• Quantity per Reel: 3000 pieces.
• Minimum Order Quantity (MOQ) for Remainders: 500 pieces.
• Cover Tape: Empty component pockets are sealed with a top cover tape.
• Missing Components: The maximum number of consecutive missing LEDs in the tape is two, in accordance with ANSI/EIA-481 standards.

8. Application Recommendations

8.1 Typical Application Circuits

An LED is a current-driven device. The most basic and reliable drive method is to use a series current-limiting resistor, as shown in the datasheet's \"Circuit A.\" For a supply voltage V_CC, the resistor value R is calculated as: R = (V_CC - V_F) / I_F. Using the maximum V_F (2.4V) for calculation ensures the current does not exceed the desired I_F even with a low-V_F part. For multiple LEDs, it is strongly recommended to use a separate resistor for each LED connected in parallel to ensure uniform brightness, as the forward voltage can vary between individual devices.

8.2 Design Considerations

• Current Setting: Operate at or below the 20mA maximum DC current. For longer life and lower power consumption, 10mA or even 5mA is often sufficient, especially for indicator purposes.
• Heat Dissipation: For continuous operation at high current, ensure the PCB layout allows heat to dissipate from the LED's thermal pad (if applicable) or the solder joints.
• Optical Design: The 130° viewing angle provides wide coverage. For more focused light, external lenses or light guides may be necessary.
• Dimming: Brightness can be controlled via Pulse Width Modulation (PWM), where the LED is switched on and off at a frequency faster than the eye can perceive (typically >100Hz). The average current, and thus the perceived brightness, is controlled by the duty cycle. This is more efficient and provides better color stability than analog (DC) dimming.

9. Technical Comparison and Differentiation

The LTST-C170KDKT's primary differentiators are its combination of technology and package:

1. AllnGaP Chip vs. Other Technologies: Compared to older GaAsP (Gallium Arsenide Phosphide) red LEDs, AllnGaP offers significantly higher luminous efficiency (more light output per unit of electrical power) and better temperature stability. This results in brighter, more consistent performance.
2. Wide Viewing Angle: The 130° angle is notably wider than many SMD LEDs designed for more directional light. This makes it excellent for applications requiring broad, even illumination rather than a focused beam.
3. Manufacturing Compatibility: Full compatibility with IR reflow and automated placement makes it a cost-effective choice for modern, high-volume surface-mount assembly lines, unlike through-hole LEDs which require manual or wave soldering.

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive this LED directly from a 3.3V or 5V microcontroller pin?
A1: No. You must always use a series current-limiting resistor. Connecting it directly would attempt to draw excessive current, potentially damaging both the LED and the microcontroller output pin. Calculate the resistor value as described in Section 8.1.

Q2: What does the luminous intensity bin code (H, J, K, L, M) mean for my design?
A2: It defines the brightness range. If your design requires a minimum brightness to meet a specification (e.g., for sunlight readability), you must select a bin that guarantees that minimum (e.g., Bin M for the highest brightness). For non-critical indicators, a lower bin may be more cost-effective.

Q3: The datasheet shows a max soldering temperature of 260°C, but my board has other components requiring 250°C. Is this OK?
A3: Yes. The 260°C rating is a maximum withstand rating. A profile with a lower peak temperature (e.g., 250°C) is perfectly acceptable and will subject the LED to less thermal stress, which is beneficial for reliability.

Q4: How long will the LED last?
A4: LED lifetime is typically defined as the point where light output degrades to 50% or 70% of its initial value (L70/L50). While not specified in this basic datasheet, AllnGaP LEDs generally have very long lifetimes (tens of thousands of hours) when operated within their ratings, especially below maximum current and with good thermal management.

11. Practical Design and Usage Case

Case: Designing a Status Indicator Panel for a Network Router
A designer needs multiple red status LEDs for \"Power,\" \"Internet,\" \"Wi-Fi,\" and \"Ethernet\" indicators on a consumer router. The LTST-C170KDKT is an excellent candidate.

1. Circuit Design: The router uses a 3.3V rail. Targeting a conservative 10mA drive current and using the maximum V_F of 2.4V for a safety margin: R = (3.3V - 2.4V) / 0.010A = 90 Ohms. The nearest standard value of 91 Ohms is selected. A separate 91-ohm resistor is used for each of the four LEDs.
2. Brightness Consistency: By using individual resistors, variations in the V_F of each LED (e.g., one is 1.8V, another is 2.2V) do not cause significant brightness differences, as the current through each is independently set by its resistor.
3. Assembly: The LEDs are placed on the PCB using the recommended pad layout. The entire board undergoes a standard lead-free IR reflow process with a peak temperature of 245°C, well within the device's rating.
4. Result: The panel provides uniform, bright red status indication with high reliability, leveraging the LED's wide viewing angle to be visible from various angles.

12. Operating Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that convert electrical energy directly into light through a process called electroluminescence. The core of the LTST-C170KDKT is a chip made of Aluminum Indium Gallium Phosphide (AllnGaP). This material is a direct bandgap semiconductor. When a forward voltage is applied, electrons from the n-type region and holes from the p-type region are injected across the junction. When these charge carriers recombine within the active region of the junction, they release energy. In an indirect bandgap material, this energy is primarily released as heat. In a direct bandgap material like AllnGaP, a significant portion of this energy is released as photons (light particles). The specific wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material, which is engineered during the crystal growth process to produce red light (~650nm peak). The water-clear epoxy package encapsulates and protects the fragile semiconductor chip, and its dome shape helps extract the light efficiently, contributing to the wide viewing angle.

13. Technology Trends

The field of LED technology continues to evolve, driven by demands for higher efficiency, lower cost, and new applications. For indicator-type LEDs like the LTST-C170KDKT, several trends are relevant:

1. Increased Efficiency: Ongoing material science research aims to improve the internal quantum efficiency (IQE) and light extraction efficiency of AllnGaP and other compound semiconductors, yielding brighter LEDs at the same drive current or the same brightness at lower power.
2. Miniaturization: There is a constant push for smaller package sizes (e.g., 0402, 0201 metric) to save PCB real estate in increasingly compact portable electronics.
3. Enhanced Reliability and Robustness: Improvements in packaging materials and die-attach techniques enhance moisture resistance, thermal cycling performance, and overall longevity.
4. Integration: While this is a discrete component, trends include integrating multiple LED chips (RGB, multi-color) into a single package or combining control ICs with LEDs for \"smart\" lighting solutions, though these are more common in lighting-grade products than basic indicators.
5. Expanded Color Gamut: Developments in materials like quantum dots or novel phosphors allow for more saturated and precise colors, which may trickle down to the indicator market for specialized display applications.

The LTST-C170KDKT represents a mature, reliable, and cost-optimized solution within this evolving landscape, well-suited for its intended applications in consumer and industrial electronics.