LTST-C191TGKT-2A SMD LED Datasheet - Transparent Lens - InGaN Green - 0.55mm Ultra-Thin - 10mA DC - 38mW - Technical Documentation

1. Product Overview

This document details the technical specifications of a miniature surface-mount LED lamp, designed for automated printed circuit board assembly and space-constrained applications. The device is an ultra-thin, ultra-high brightness LED that emits green light using an InGaN semiconductor chip. Its compact form factor and compatibility with modern manufacturing processes make it a versatile component in a wide range of electronic devices.

1.1 Core Advantages and Target Market

The main advantages of this LED include its extremely low 0.55mm thickness, facilitating integration into ultra-thin devices. Its InGaN chip can provide high luminous intensity. The component fully complies with the RoHS (Restriction of Hazardous Substances) directive. It is packaged on an EIA-standard 8mm tape, wound on a 7-inch reel, fully compatible with high-speed automated pick-and-place equipment. Furthermore, its design can withstand the infrared reflow soldering process, a standard process for Surface Mount Technology (SMT) assembly lines.

The target application areas are broad, covering communication equipment, office automation equipment, home appliances, and industrial equipment. Specific use cases include keyboard and keypad backlighting, status indicators, miniature displays, and various signal or symbol illumination applications.

2. In-depth Technical Parameter Analysis

This section provides a detailed and objective interpretation of the electrical, optical, and thermal characteristics defined in the datasheet. Understanding these parameters is crucial for reliable circuit design and ensuring long-term performance.

2.1 Absolute Maximum Ratings

These ratings define the stress limits that may cause permanent damage to the device. They are not intended for normal operating conditions.

• Power Dissipation (Pd):38 mW. Wannan shine matsakaicin zafi da LED ɗin ke iya ɓarkewa a yanayin zafin muhalli (Ta) na 25°C. Wuce wannan iyaka yana da haɗarin yin zafi da sauri da tsufa.
• Ƙarfin lantarki na gaba (IF):10 mA. Matsakaicin ƙarfin lantarki na gaba mai ci gaba da za a iya amfani da shi.
• Matsakaicin ƙarfin lantarki na gaba:40 mA. This current is only allowed under pulse conditions with a duty cycle of 1/10 and a pulse width of 0.1ms. It allows for higher brightness in a short period without causing thermal damage.
• Operating Temperature Range:-20°C to +80°C. The ambient temperature range within which the LED is specified to operate normally.
• Temperature Range for Storage:-30°C to +100°C. Temperature range for storage when the device is not powered.
• Infrared Soldering Conditions:260°C for 10 seconds. This defines the peak temperature and time profile that the LED can withstand during the reflow soldering process, which is critical for lead-free assembly processes.

2.2 Electro-Optical Characteristics at Ta=25°C

These are typical performance parameters measured under standard test conditions. Designers should use these values for circuit calculations.

• Luminous Intensity (Iv):At a forward current (IF) of 2 mA, the range is from 11.2 mcd (minimum) to 112.0 mcd (maximum). This wide range is managed through a binning system (see Section 3). This parameter measures the brightness perceived by the human eye.
• Viewing Angle (2θ1/2):130 degrees. This is the full angle at which the luminous intensity drops to half of the axial measured value. A 130-degree angle indicates a wide viewing angle mode, suitable for applications requiring observation of light from different angles.
• Peak Emission Wavelength (λP):530 nm. This is the wavelength at which the LED's spectral output is strongest.
• Dominant Wavelength (λd):525.0 nm to 545.0 nm (at IF=2mA). This is the single wavelength perceived by the human eye that defines the color (green). It is derived from the CIE chromaticity diagram and differs from the peak wavelength.
• Spectral Line Half-Width (Δλ):35 nm. This indicates the spectral purity or bandwidth of the emitted light, measured as the width at half of the maximum intensity.
• Forward Voltage (VF):2.30 V to 3.30 V (at IF=2 mA). The voltage drop when the LED is conducting current. This range is also affected by binning.
• Reverse Current (IR):At a reverse voltage (VR) of 5V, the maximum is 10 μA. This device is not designed for reverse operation; this test is for quality verification only. Applying reverse voltage must be avoided in the circuit, typically by ensuring correct polarity or using protection circuits.

2.3 Thermal Considerations

Although no explicit chart is provided, thermal management can be inferred from the power dissipation rating and operating temperature range. The low power rating of 38mW emphasizes that this is a low-power device. However, in high-density layouts or confined spaces, it is recommended to ensure sufficient heat dissipation through PCB pads to keep the junction temperature within safe limits, thereby maintaining light output and lifespan.

3. Grading System Description

To ensure color and brightness consistency in production, LEDs are sorted into different bins based on key parameters. This allows designers to select specific performance grades for their applications.

3.1 Forward Voltage (Vf) Binning

LEDs are classified based on their forward voltage drop at 2 mA. The binning range is from D4 (2.30V - 2.50V) to D8 (3.10V - 3.30V), with a tolerance of ±0.1V per bin. Selecting a narrow Vf bin helps ensure uniform brightness when multiple LEDs are driven in parallel from a constant voltage source.

3.2 Luminous Intensity (Iv) Binning

This binning controls the luminous intensity output. The bin range is from L (11.2 - 18.0 mcd) to Q (71.0 - 112.0 mcd), measured at 2 mA, with a tolerance of ±15% per bin. Applications requiring a specific brightness level (e.g., indicator lights with specified photometric classes) will specify the Iv bin.

3.3 Binning of Hue (Dominant Wavelength)

This ensures color consistency. The dominant wavelength bins for this green LED are: AQ (525.0 - 530.0 nm), AR (530.0 - 535.0 nm), AS (535.0 - 540.0 nm), and AT (540.0 - 545.0 nm), with a tolerance of ±1nm. Specifying a narrow hue bin is essential for applications where precise color matching is critical (e.g., multi-color displays or traffic signals).

4. Performance Curve Analysis

The datasheet references typical performance curves. While the specific graphs are not reproduced in the provided text, their standard interpretation is crucial for design.

4.1 Forward Current vs. Forward Voltage (I-V Curve)

Wannan lanƙwasa yana nuna alaƙar da ba ta layi ba tsakanin kwararar da ke gudana ta LED da ƙarfin lantarki a ƙarshensa. A zahiri, alaƙar ta zama mai ma'ana ta ƙima. Ƙimar VF da aka bayar (misali, kusan 2.8V a 2mA) wani batu ne a kan wannan lanƙwasa. Masu ƙira suna amfani da wannan lanƙwasa don tantance ƙimar resistor da ake buƙata don iyakance kwarara a cikin ƙarfin lantarki da aka bayar. Yawanci, ana fifita amfani da tushen kwarara mai dorewa don kunna LED, maimakon tushen ƙarfin lantarki mai dorewa tare da resistor a jere, saboda yana ba da haske mafi kwanciyar hankali, kuma yana da juriya mafi kyau ga sauye-sauyen Vf.

4.2 Luminous Intensity vs. Forward Current

This graph typically shows that luminous intensity increases with forward current, but not in a linear relationship. At higher currents, efficiency may decrease due to increased heat generation. The rated DC current of 10mA represents a point that achieves a good balance between brightness and reliability. Operating near the absolute maximum current will shorten the lifespan.

4.3 Spectral Distribution

The spectral output graph will show the relationship between intensity and wavelength, centered at a peak of 530nm and a half-width of 35nm. This information is crucial for applications sensitive to specific wavelengths, such as optical sensors or color filter systems.

4.4 Temperature Dependence

Although not detailed, LED performance is sensitive to temperature. Typically, the forward voltage decreases with increasing temperature (negative temperature coefficient), and the light output also decreases. For precision applications, these effects must be considered, especially when the LED operates in varying thermal environments.

5. Mechanical and Packaging Information

5.1 Package Dimensions and Polarity

Wannan LED yana da siririn siffa mai kauri 0.55mm. Girman kunsa an bayar da shi a cikin littafin ƙayyadaddun bayanai, daidaitaccen ƙimar kuskure shine ±0.1mm. Ruwan tabarau yana da haske. Ana gano cathode ta hanyar alamar da ke kan kunsa (kamar tsaga, kore-dot, ko yanke kusurwa). Dole ne a gane polarity daidai yayin haɗawa don hana lalacewa ta hanyar jujjuyawar baya.

5.2 Recommended PCB Land Pattern Design

An ba da shawarar tsarin pad (kunsa) don tabbatar da ingantaccen haɗin gwiwa da kwanciyar hankali na inji. Yin bin wannan ƙira yana da mahimmanci don samar da kusurwar haɗin gwiwar daidai, sarrafa zafi, da hana tombstone (kayan aikin suna tasowa a ƙarshen lokacin sake zafi). Ƙirar pad kuma tana taimakawa wajen daidaita kayan aikin yayin aikin saka ta atomatik.

6. Soldering, Assembly and Handling Guidelines

6.1 Welding Process Guide

This LED is compatible with infrared reflow soldering. A recommended temperature profile for lead-free processes is provided, with key parameters as follows:

• Preheating:150-200°C.
• Preheating time:Maximum 120 seconds, to gradually heat the circuit board and components.
• Peak temperature:Maximum 260°C.
• Time above liquidus (at peak):Maximum 10 seconds. The temperature profile must comply with JEDEC standards to ensure reliability.

Manual soldering with a soldering iron is permissible but must be controlled: temperature ≤300°C and time ≤3 seconds, for a single operation only. Excessive heat from the iron can easily damage the LED or its epoxy lens.

6.2 Cleaning

If cleaning is required after soldering, only the specified solvents should be used. The datasheet recommends immersion in ethanol or isopropanol at room temperature for no more than one minute. Unspecified or highly corrosive chemicals may damage the package material or the optical lens.

6.3 Storage and Moisture Sensitivity

Wannan LED yana da hankali ga danshi. Lokacin da aka rufe jakar kariya daga danshi (mai cikin abin bushewa) ba a buɗe ba, ya kamata a adana shi a ≤30°C da ≤90% danshin dangi (RH), kuma a yi amfani da shi cikin shekara guda. Da zarar an buɗe fakitin asali, yanayin ajiya bai kamata ya wuce 30°C / 60% RH ba. Abubuwan da aka ciro daga fakitin asali ya kamata a yi musu infrared reflow soldering cikin sa'o'i 672 (kwanaki 28, matakin MSL2a). Idan an adana su a waje da jakar asali na tsawon lokaci, dole ne a gasa su a kusan 60°C na akalla sa'o'i 20 kafin a yi soldering, don kawar da ruwan da aka sha da kuma hana "popcorn" phenomenon (fashewar kulli saboda matsi na tururi a lokacin reflow soldering).

6.4 Electrostatic Discharge (ESD) Protection Measures

Wannan LED yana da saukin lalacewa ta hanyar zubar da wutar lantarki (ESD) da kuma kwararar wutar lantarki. Ana ba da shawarar yin amfani da bandeji na wuyan ƙasa ko safofin hannu masu hana wutar lantarki lokacin sarrafa na'urar. Duk kayan aiki, wuraren aiki, da injuna dole ne a ƙasa su yadda ya kamata don hana tarin wutar lantarki.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

LEDs are supplied in embossed carrier tape with protective cover tape, wound on 7-inch (178mm) diameter reels. The standard reel quantity is 5,000 pieces. The tape width is 8mm. The packaging conforms to the ANSI/EIA-481 specification. There are guidelines for the minimum packaging quantity of remnants and the maximum number of consecutive missing components in the tape.

8. Application Description and Design Considerations

8.1 Typical Application Circuit

The most common driving method is to connect a current-limiting resistor in series. The formula for calculating the resistor value (R) is: R = (Power Supply Voltage - LED Forward Voltage) / Desired Current. For example, with a 5V power supply, a typical VF of 2.8V, and a desired current of 5mA: R = (5 - 2.8) / 0.005 = 440 ohms. A standard 470-ohm resistor is suitable. For better brightness stability under variations in temperature and power supply voltage, it is recommended to use a simple constant current source composed of a transistor or a dedicated LED driver IC, especially for multiple LEDs or critical brightness applications.

8.2 Design Considerations

• Current Drive:Always use controlled current drive, not a fixed voltage directly. Treat absolute maximum ratings as limits, not targets.
• Thermal Management:Ensure the PCB layout provides sufficient copper area for the LED pads to act as heat sinks, especially when operating near maximum current.
• Optical Design:The wide 130-degree viewing angle provides good off-axis visibility. For focused light, an external lens or light guide may be required.
• Reverse Voltage Protection:If there is a possibility of reverse voltage being applied (e.g., in AC circuits or with inductive loads), a protection diode must be connected in parallel across the LED (cathode to anode).

8.3 Application Limitations

The datasheet contains a warning that these LEDs are suitable for general electronic equipment. For applications requiring extremely high reliability where failure could endanger life or health (aviation, medical equipment, critical safety systems), consultation with the manufacturer is required before design adoption. This is a standard disclaimer for commercial-grade components.

9. Technical Comparison and Differentiation

Compared to green LEDs based on older technologies such as AlGaInP, this InGaN-based green LED typically offers higher luminous efficacy and better performance stability. The 0.55mm height is a key differentiator in the market, enabling designs thinner than those using standard 0.6mm or 0.8mm height LEDs. Its compatibility with standard infrared reflow soldering and tape-and-reel packaging aligns it with mainstream, cost-effective SMT assembly processes, unlike some specialized LEDs that may require special handling.

10. Frequently Asked Questions (FAQ)

10.1 What is the difference between peak wavelength and dominant wavelength?

Peak Wavelength (λP) is the physical wavelength at which an LED emits its strongest optical power. Dominant Wavelength (λd) is a value calculated based on human color perception (CIE chart) and best represents the color we see. For monochromatic green LEDs, they are usually close but not identical.

10.2 Zan iya amfani da 20mA don tuka wannan LED don samun ƙarin haske?

No. The absolute maximum rating for DC forward current is 10 mA. Operating at 20mA will exceed this rating, leading to overheating, accelerated lumen depreciation, and potential catastrophic failure. For higher brightness, please select an LED with a higher Iv bin (e.g., Q bin), or choose a product rated for a higher current.

10.3 Me ya sa rarrabuwa ke da muhimmanci?

Manufacturing variations cause differences in Vf, Iv, and color between individual LEDs. Binning classifies them into groups with tightly controlled parameters. For products using multiple LEDs (e.g., backlight arrays), using LEDs from the same bin ensures uniform brightness and color, which is crucial for aesthetic and functional quality.

10.4 How to understand the "Infrared Reflow Conditions" rating?

Wannan yana nufin cewa LED na iya rayuwa a cikin tsarin zafin jiki na sake walda, inda jikin kayan ya kai kololuwar 260°C, tsawon lokaci har zuwa dakika 10. Wannan shine daidaitaccen buƙatu na man walda maras gubar, wanda yake da narkewar zafi mafi girma fiye da tsohuwar gubar da aka yi da tagulla.

11. Practical Design and Usage Examples

11.1 Mobile Device Keyboard Backlight

In mobile phone keyboards, multiple LEDs are typically placed beneath the light guide plate. Using LEDs with the same Iv and tint bin (e.g., intensity bin N, color bin AR) ensures each key is uniformly illuminated with the same hue. A height of 0.55mm is crucial here to fit within the space constraints of ultra-slim designs. They are driven in parallel, either through individual series resistors or by a dedicated backlight driver IC that provides constant current.

11.2 Network Router Status Indicator

A single LED can be used to indicate power, network activity, or error status. The 130-degree wide viewing angle allows the status to be seen from almost any direction in the room. A simple circuit consisting of a microcontroller GPIO pin, a series resistor (e.g., 330 ohms when driving 5mA from a 3.3V supply), and an LED is sufficient. Software can control the blinking pattern.

12. Brief Introduction to Working Principle

This LED is a semiconductor photonic device. It is based on an InGaN heterostructure. When a forward voltage is applied, electrons and holes are injected into the active region of the semiconductor chip. They recombine, releasing energy in the form of photons (light). The specific composition of the InGaN alloy determines the bandgap energy, which directly defines the wavelength (color) of the emitted light—in this case, green. A transparent epoxy resin lens encapsulates the chip, providing mechanical protection and shaping the light output pattern.

13. Technology Trends

The development of InGaN materials was a breakthrough for achieving efficient green and blue LEDs, enabling white LEDs (via phosphor conversion) and full-color displays. Current trends for SMD LEDs continue toward higher luminous efficacy (more light output per watt), lower thermal resistance for better power handling, and smaller package sizes. There is also a focus on improving color rendering and consistency for lighting applications. The drive for miniaturization in consumer electronics pushes packaging toward thinner heights and smaller footprints, as exemplified by this 0.55mm component.