SMD LED LTST-M670KGKT Datasheet - AlInGaP Green - 2.4V - 72mW - English Technical Document

1. Product Overview

The LTST-M670KGKT is a high-brightness, surface-mount LED designed for modern electronic applications. It utilizes an Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material to produce a green light output. The device is housed in a standard EIA-compatible package with a water-clear lens, which helps maximize light extraction and provides a wide viewing angle. This LED is specifically engineered for compatibility with automated pick-and-place assembly equipment and infrared (IR) reflow soldering processes, making it suitable for high-volume manufacturing. Its core advantages include consistent performance, environmental compliance, and ease of integration into automated production lines.

2. Technical Parameter Deep Dive

2.1 Absolute Maximum Ratings

The device's operational limits are defined at an ambient temperature (Ta) of 25°C. Exceeding these ratings may cause permanent damage. The maximum continuous forward current (DC) is 30 mA. For pulsed operation, a peak forward current of 80 mA is permissible under a 1/10 duty cycle with a 0.1ms pulse width. The maximum power dissipation is 72 mW. The LED can withstand a reverse voltage of up to 5 V. The operating temperature range is from -40°C to +85°C, and the storage temperature range extends from -40°C to +100°C.

2.2 Electrical and Optical Characteristics

Key performance parameters are measured at Ta=25°C and a forward current (IF) of 20 mA. The typical forward voltage (VF) is 2.4 V, with a range from 2.0 V to 2.4 V. The luminous intensity (IV) has a typical value of 180 millicandelas (mcd), with a minimum specified value of 56 mcd. The viewing angle (2θ1/2), defined as the full angle where intensity drops to half its axial value, is 120 degrees. The peak emission wavelength (λP) is 574 nm, and the dominant wavelength (λd) is 571 nm. The spectral line half-width (Δλ) is 15 nm. The reverse current (IR) is a maximum of 10 μA when a reverse voltage (VR) of 5 V is applied.

3. Binning System Explanation

The product is classified into bins based on three key parameters to ensure consistency in application. This allows designers to select LEDs with tightly grouped characteristics for uniform appearance and performance in their designs.

3.1 Forward Voltage Binning

Forward voltage is binned in 0.2 V steps. Bin codes are D2 (1.80V - 2.00V), D3 (2.00V - 2.20V), and D4 (2.20V - 2.40V). A tolerance of ±0.1 V is applied to each bin.

3.2 Luminous Intensity Binning

Luminous intensity is categorized into five bins: P2 (56.0 - 71.0 mcd), Q1 (71.0 - 90.0 mcd), Q2 (90.0 - 112.0 mcd), R1 (112.0 - 140.0 mcd), and R2 (140.0 - 180.0 mcd). Each bin has a tolerance of ±11%.

3.3 Dominant Wavelength Binning

The dominant wavelength, which defines the perceived color, is binned as follows: B (564.5 - 567.5 nm), C (567.5 - 570.5 nm), D (570.5 - 573.5 nm), and E (573.5 - 576.5 nm). The tolerance for each bin is ±1 nm.

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), the provided data allows for analysis of key relationships. The forward voltage shows a logarithmic relationship with forward current, typical of diode behavior. Luminous intensity is directly proportional to forward current within the specified operating range. The spectral characteristics, with a peak at 574 nm and a narrow 15 nm half-width, indicate a pure, saturated green color. The wide 120-degree viewing angle suggests a lambertian or near-lambertian radiation pattern, providing good off-axis visibility.

5. Mechanical and Package Information

5.1 Device Dimensions

The LED conforms to a standard EIA surface-mount package outline. All critical dimensions, including body length, width, height, and lead spacing, are provided in the datasheet drawings with a general tolerance of ±0.2 mm. The package is designed for stable placement during assembly.

5.2 Polarity Identification

The cathode is typically identified by a visual marker on the package, such as a notch, a dot, or a green marking, as indicated in the package drawing. Correct polarity orientation is crucial for circuit operation.

5.3 Recommended PCB Pad Layout

A land pattern design is suggested for the printed circuit board to ensure reliable solder joint formation during reflow soldering. This pattern accounts for proper solder fillet formation and thermal relief.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Profile

The device is compatible with lead-free IR reflow soldering. A recommended profile is provided, aligned with the J-STD-020B standard. Key parameters include a preheat temperature of 150-200°C, a preheat time of up to 120 seconds, and a peak temperature not exceeding 260°C for a maximum of 10 seconds. The profile should be characterized for the specific PCB assembly.

6.2 Hand Soldering

If hand soldering is necessary, a soldering iron tip temperature should not exceed 300°C, and contact time should be limited to a maximum of 3 seconds for a single operation only.

6.3 Cleaning

If cleaning is required after soldering, only specified alcohol-based solvents like ethyl alcohol or isopropyl alcohol should be used. The LED should be immersed at normal temperature for less than one minute. Unspecified chemicals may damage the package.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied in embossed carrier tape with a width of 8 mm, wound onto 7-inch (178 mm) diameter reels. Each reel contains 2000 pieces. The tape is sealed with a top cover tape. A minimum order quantity of 500 pieces is available for remainders.

7.2 Packaging Standards

Packaging complies with EIA-481-1-B specifications. The maximum number of consecutive missing components in the tape is two.

8. Storage and Handling

For unopened moisture-proof bags containing desiccant, LEDs should be stored at ≤30°C and ≤70% Relative Humidity (RH) and used within one year. Once the original packaging is opened, the storage environment must not exceed 30°C and 60% RH. Components removed from their original packaging should undergo IR reflow within 168 hours (7 days). For storage beyond this period, they should be kept in a sealed container with desiccant or in a nitrogen desiccator. LEDs stored out of packaging for more than 168 hours require baking at approximately 60°C for at least 48 hours prior to soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

9. Application Notes and Design Considerations

9.1 Drive Circuit Design

LEDs are current-operated devices. To ensure uniform brightness and prevent current hogging, a current-limiting resistor must be used in series with each LED or each parallel branch of LEDs when connected in parallel. Driving the LED with a constant current source is the most effective method for maintaining stable luminous output. The resistor value can be calculated using Ohm's Law: R = (Vcc - VF) / IF, where Vcc is the supply voltage, VF is the LED forward voltage (use max value for design margin), and IF is the desired forward current (e.g., 20 mA).

9.2 Thermal Management

Although power dissipation is relatively low (72 mW max), proper thermal design on the PCB is important for long-term reliability, especially when operating at high ambient temperatures or at high currents. Ensuring adequate copper area around the LED pads helps dissipate heat.

9.3 Typical Application Scenarios

This LED is suitable for a wide range of applications including status indicators, backlighting for icons or symbols, panel illumination, consumer electronics, and general-purpose signaling. Its compatibility with automated processes makes it ideal for high-volume products.

10. Technical Comparison and Differentiation

The use of AlInGaP technology for green light offers advantages over traditional Gallium Phosphide (GaP) based green LEDs, typically providing higher efficiency and brighter output. The 120-degree viewing angle is wider than many niche \"high-directionality\" LEDs, making it versatile for applications requiring wide-angle visibility. The explicit compatibility with JEDEC-standard IR reflow profiles differentiates it from LEDs that may only be suitable for hand soldering or wave soldering, aligning it with modern SMT assembly lines.

11. Frequently Asked Questions (FAQ)

Q: Can I drive this LED without a current-limiting resistor?
A: No. Operating an LED directly from a voltage source is not recommended and will likely destroy the device due to excessive current. Always use a series resistor or constant current driver.

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength (λP) is the wavelength at which the spectral power distribution is maximum. Dominant wavelength (λd) is derived from the CIE chromaticity diagram and represents the single wavelength of the spectrum that matches the perceived color of the LED. λd is more relevant for color specification.

Q: How do I interpret the bin code in the part number?
A: The specific bin codes for VF, IV, and λd are not embedded in the base part number LTST-M670KGKT. They are assigned during manufacturing and should be specified at the time of ordering based on the bin tables provided in the datasheet to ensure you receive LEDs with the desired characteristics.

Q: Is baking always necessary before soldering?
A: Baking is required only if the components have been exposed to ambient conditions outside their original moisture-proof bag for more than 168 hours. This is to prevent moisture-induced package cracking during the high-temperature reflow process.

12. Design and Usage Case Study

Consider a design for a multi-indicator status panel on an industrial controller. Ten green status LEDs are required. To ensure uniform brightness, LEDs from the same luminous intensity bin (e.g., R1: 112-140 mcd) should be selected. To simplify the driver circuit, all LEDs can be connected in parallel, each with its own current-limiting resistor calculated for a 5V supply: R = (5V - 2.4V) / 0.02A = 130 Ohms (a standard 130 or 150 Ohm resistor can be used). The PCB layout should incorporate the recommended pad geometry and provide some small thermal relief traces. The assembly would use the specified IR reflow profile. This approach guarantees consistent visual performance and reliable manufacturing.

13. Technology Principle Introduction

The LTST-M670KGKT is based on Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the active region. Their recombination releases energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which in turn dictates the wavelength (color) of the emitted light—in this case, green. The water-clear epoxy lens is not tinted; its function is to protect the semiconductor die, shape the radiation pattern to a wide viewing angle, and enhance light extraction from the chip.

14. Industry Trends and Developments

The trend in SMD LEDs for indicator applications continues towards higher efficiency (more light output per unit of electrical power), smaller package sizes for higher density boards, and improved color consistency through tighter binning. There is also a strong drive for enhanced reliability under harsh conditions and compatibility with lead-free, high-temperature soldering processes. The move towards automation in all manufacturing sectors underscores the importance of components like this one that are designed for tape-and-reel packaging and reflow soldering, reducing manual labor and increasing production throughput and consistency.