LTST-C198KGKT SMD LED Datasheet - 0.2mm Thin - 2.6V Forward Voltage - AlInGaP Green - 78mW Power - English Technical Document

1. Product Overview

The LTST-C198KGKT is an ultra-thin, surface-mount chip LED designed for modern, compact electronic applications. Its primary feature is an exceptionally low profile of just 0.2 millimeters, making it suitable for devices where space and component height are critical constraints. The device utilizes an AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material to produce a high-brightness green light output. It is packaged in industry-standard 8mm tape on 7-inch reels, ensuring compatibility with high-speed automated pick-and-place assembly equipment and infrared reflow soldering processes. This LED is classified as a green product and complies with RoHS (Restriction of Hazardous Substances) directives.

1.1 Core Advantages

The key advantages of this component stem from its combination of miniaturization and performance. The 0.2mm thickness allows for integration into extremely slim products. The AlInGaP chip technology provides superior luminous efficiency compared to traditional materials, resulting in high brightness from a small form factor. Full compatibility with automated SMT (Surface Mount Technology) assembly lines streamlines manufacturing and reduces production costs. Its design is also I.C. (Integrated Circuit) compatible, allowing for direct drive from standard logic-level outputs.

2. Technical Parameter Deep Dive

This section provides a detailed, objective analysis of the electrical, optical, and thermal characteristics specified in the datasheet.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. They are not intended for normal operation. The maximum continuous forward current (DC) is 30 mA. A higher peak forward current of 80 mA is permissible but only under pulsed conditions with a 1/10 duty cycle and a 0.1ms pulse width to prevent overheating. The maximum reverse voltage that can be applied is 5V. Exceeding this can cause junction breakdown. The device can dissipate up to 78 mW of power. The operating temperature range is from -30°C to +85°C, and it can be stored in temperatures from -40°C to +85°C. For soldering, it can withstand an infrared reflow peak temperature of 260°C for a maximum of 10 seconds.

2.2 Electrical & Optical Characteristics

These parameters are measured at a standard test condition of 25°C ambient temperature and a forward current (IF) of 20 mA, unless otherwise noted. The luminous intensity (Iv) has a typical value of 60.0 millicandelas (mcd), with a minimum specified value of 36.0 mcd. This intensity is measured using a sensor and filter that mimics the human eye's photopic response. The viewing angle (2θ1/2), defined as the full angle where intensity drops to half of its on-axis value, is 130 degrees, indicating a wide viewing pattern. The dominant wavelength (λd), which defines the perceived color, is 570 nm (green). The peak emission wavelength (λp) is 574 nm. The spectral line half-width (Δλ) is 15 nm, describing the spectral purity. The forward voltage (VF) typically ranges from 2.1V to 2.6V at 20mA. The reverse current (IR) is a maximum of 10.0 μA when a 5V reverse bias is applied.

3. Binning System Explanation

To ensure consistency in production, LEDs are sorted into performance bins. The LTST-C198KGKT uses a two-dimensional binning system based on luminous intensity and dominant wavelength.

3.1 Luminous Intensity Binning

Luminous intensity is categorized into three bins: N2 (36.0 - 45.0 mcd), P (45.0 - 71.0 mcd), and Q (71.0 - 112.0 mcd). A tolerance of +/-15% is applied within each bin. This allows designers to select LEDs based on the required brightness level for their application, ensuring visual uniformity in products using multiple LEDs.

3.2 Dominant Wavelength Binning

The dominant wavelength, which determines the exact shade of green, is sorted into three bins: 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. This tight control is crucial for applications where color consistency is important, such as in status indicators or full-color displays.

4. Performance Curve Analysis

While specific graphs are referenced in the datasheet (Fig.1, Fig.5), their implications can be discussed. The relationship between forward current (IF) and forward voltage (VF) is typically exponential, following the diode equation. Designers must account for the VF range when designing current-limiting circuits. The luminous intensity versus forward current curve is generally linear within the operating range but will saturate at higher currents due to thermal effects. The temperature dependence of forward voltage is negative (VF decreases as temperature increases), which is a standard characteristic of semiconductor diodes. The spectral distribution curve would show a peak at 574 nm with a width of 15 nm at half maximum.

5. Mechanical & Packaging Information

5.1 Package Dimensions and Polarity

The LED features an EIA standard package outline. The cathode is clearly identified in the tape and reel packaging diagram. Precise dimensional drawings are provided in the datasheet, with all measurements in millimeters and a general tolerance of ±0.10 mm. The ultra-thin 0.2mm profile is a key mechanical specification.

5.2 Recommended Solder Pad Design

A suggested solder pad layout is provided to ensure reliable solder joint formation and proper alignment during reflow. The recommendation includes a maximum stencil thickness of 0.08mm to control solder paste volume and prevent bridging or tombstoning of the very small component.

6. Soldering & Assembly Guide

6.1 Reflow Soldering Profile

A suggested infrared reflow profile for lead-free (Pb-free) solder processes is provided, compliant with JEDEC standards. Key parameters include a pre-heat zone of 150-200°C, a maximum pre-heat time of 120 seconds, a peak temperature not exceeding 260°C, and a time above liquidus (at peak temperature) limited to a maximum of 10 seconds. The profile is designed to minimize thermal stress on the LED package while ensuring proper solder reflow.

6.2 Storage and Handling Conditions

Electrostatic discharge (ESD) can damage the LED. Handling with grounded wrist straps and on properly grounded equipment is mandatory. For storage, unopened moisture-proof bags with desiccant should be kept at ≤30°C and ≤90% RH, with a shelf life of one year. Once opened, LEDs should be stored at ≤30°C and ≤60% RH and used within one week. If stored longer out of the original bag, they should be baked at 60°C for at least 20 hours before soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

6.3 Cleaning

If cleaning is necessary after soldering, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute is recommended. Unspecified chemicals may damage the package material or the lens.

7. Packaging & Ordering Information

The standard packaging is 8mm tape on 7-inch (178mm) diameter reels. Each full reel contains 5000 pieces. For quantities less than a full reel, a minimum packing quantity of 500 pieces applies for remainder lots. The tape and reel specifications follow ANSI/EIA 481 standards. The tape has a top cover to protect components, and the maximum allowed number of consecutive missing components in the tape is two.

8. Application Suggestions

8.1 Typical Application Scenarios

This LED is intended for ordinary electronic equipment. Its thin profile makes it ideal for backlighting in ultra-slim consumer electronics (smartphones, tablets, laptops), status indicators in portable devices, and panel illumination in instrumentation. Its high brightness and wide viewing angle suit it for applications requiring good visibility.

8.2 Design Considerations

Circuit designers must implement proper current limiting, typically using a series resistor, to ensure the forward current does not exceed the maximum DC rating of 30 mA. The forward voltage variation (2.1V to 2.6V) must be accounted for in power supply design. For visual uniformity in multi-LED arrays, specifying LEDs from the same intensity and wavelength bin is crucial. The PCB layout must follow the recommended solder pad dimensions and stencil guidelines to ensure reliable assembly.

9. Technical Comparison & Differentiation

The primary differentiation of the LTST-C198KGKT lies in its combination of extreme thinness (0.2mm) and the use of AlInGaP technology. Compared to older GaP (Gallium Phosphide) green LEDs, AlInGaP offers significantly higher luminous efficiency and better temperature stability. Compared to other thin LEDs, its specified 130-degree viewing angle is notably wide, providing better off-axis visibility. Its compatibility with standard IR reflow and tape-and-reel packaging makes it a drop-in solution for automated high-volume production, unlike some older through-hole or manually placed LEDs.

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 use a current-limiting resistor. The forward voltage is ~2.6V max. Connecting 3.3V directly would allow excessive current to flow, potentially destroying the LED. Calculate the resistor value using R = (Vcc - Vf) / If.

Q: What does the \"Peak Forward Current\" rating mean?
A: It means you can briefly pulse the LED with up to 80mA to achieve higher instantaneous brightness, but only under very specific conditions: a pulse width of 0.1ms and a duty cycle of 10% or less. This is not for continuous operation.

Q: Why is baking required if the LEDs are stored outside the bag?
A: The plastic package can absorb moisture from the air. During the rapid heating of reflow soldering, this moisture can vaporize explosively, causing internal delamination or cracking (\"popcorning\"). Baking drives out this absorbed moisture.

11. Practical Design Case

Consider designing a status indicator for a wearable device. The device has a rigid-flex PCB with height constraints under 0.3mm in the indicator area. The LTST-C198KGKT, at 0.2mm thick, fits perfectly. A green indicator is required to show \"fully charged.\" The designer selects LEDs from bin \"P\" for intensity and bin \"D\" for wavelength to ensure consistent color and brightness across all units. The LED is driven at 15 mA (well below the 30 mA max) via a current-limiting resistor from the device's 3.0V battery rail, providing ample brightness with low power consumption. The PCB layout uses the recommended pad geometry, and the assembly house uses the provided reflow profile, resulting in reliable, high-yield production.

12. Technology Principle Introduction

The LED is based on a semiconductor p-n junction made from AlInGaP materials. When a forward voltage is applied, electrons and holes are injected into the active region where they recombine. This recombination process releases energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy of the semiconductor, which directly defines the wavelength (color) of the emitted light—in this case, green at around 570 nm. The ultra-thin package is achieved by using a chip-scale LED die with a minimal amount of encapsulating material, unlike traditional LEDs with a molded plastic lens.

13. Technology Trends

The trend in indicator and backlight LEDs continues toward further miniaturization, higher efficiency, and better color consistency. Package heights are moving from 0.2mm toward even thinner profiles. There is a growing use of advanced semiconductor materials like InGaN (for blue/green/white) and AlInGaP (for red/orange/yellow/green) to replace less efficient materials. Integration is another trend, with multi-LED arrays or LEDs combined with driver ICs in single packages. Furthermore, the drive for energy efficiency pushes for higher lumens-per-watt ratings, reducing power consumption in end applications. Automated testing and tighter binning specifications are becoming standard to meet the demands of high-resolution displays and applications requiring precise color matching.