LTST-S220KSKT Yellow SMD LED Datasheet - EIA Package - Voltage 2.4V - Power 75mW - Technical Documentation

1. Product Overview

LTST-S220KSKT is a surface-mount device (SMD) light-emitting diode (LED) designed for modern electronic assembly processes. It belongs to the side-view chip LED series, meaning its primary light emission direction is parallel to the mounting plane of the printed circuit board (PCB). This orientation is particularly useful for applications requiring edge lighting or status indicators visible from the side of a device. The LED uses aluminum indium gallium phosphide (AlInGaP) semiconductor material, known for producing high-efficiency light in the yellow to red spectral range. The device is encapsulated in a clear lens that does not diffuse light, resulting in a more focused and intense beam suitable for indicator purposes.

The core advantages of this component include its compliance with the RoHS (Restriction of Hazardous Substances) directive, making it suitable for global markets with strict environmental regulations. It features tin-plated leads to enhance solderability and corrosion resistance. The package is standardized according to EIA (Electronic Industries Alliance) specifications, ensuring compatibility with various automated pick-and-place equipment used in high-volume manufacturing. Furthermore, it is designed to withstand infrared (IR) reflow soldering processes, the standard process for assembling lead-free (Pb-free) solder joints in surface-mount technology.

The target market for this LED includes consumer electronics, industrial control panels, automotive interior lighting, instrumentation, and any application requiring a reliable, bright, yellow status indicator that can be integrated via automated assembly lines.

2. In-depth and Objective Interpretation of Technical Parameters

2.1 Absolute Maximum Ratings

These ratings define the stress limits that may cause permanent damage to the device. Operation at or beyond these limits is not guaranteed. Absolute maximum ratings are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd):75 mW. This is the maximum power that the LED package can dissipate as heat without degrading its performance or lifespan. Exceeding this limit risks thermal damage.
• Peak Forward Current (IFP):80 mA. This is the maximum allowable instantaneous forward current, typically specified under pulse conditions (1/10 duty cycle, 0.1ms pulse width) to prevent excessive junction temperature rise.
• DC Forward Current (IF):30 mA. This is the recommended maximum continuous forward current for reliable long-term operation. The typical operating condition for testing optical characteristics is 20 mA.
• Reverse Voltage (VR):5 V. Applying a reverse voltage higher than this value may cause the PN junction breakdown of the LED and irreversible damage.
• Operating Temperature Range:-30°C to +85°C. The LED is designed to operate within this ambient temperature range.
• Storage Temperature Range:-40°C to +85°C. The device can be stored in a non-operating state within this wider temperature range.
• Infrared soldering conditions:260°C for 10 seconds. This defines the peak temperature and time tolerance for the reflow soldering process, which is critical for lead-free assembly.

2.2 Electro-Optical Characteristics

These parameters are measured under standard test conditions (Ta=25°C, IF=20mA) and define the performance of the device.

• Luminous Intensity (Iv):18.0 - 54.0 mcd (typical). This measures the LED brightness as perceived by the human eye (photopic vision). The wide range indicates the use of a binning system (see Section 3). Intensity is measured using a filter that simulates the CIE human eye response curve.
• Viewing Angle (2θ1/2):130 degrees (typical). This is the full angle at which the luminous intensity drops to half of its value on the central axis (0°). A 130° angle indicates a relatively wide emission pattern.
• Peak Emission Wavelength (λP):591 nm (typical). This is the wavelength at which the LED's spectral power output is maximum. It falls within the yellow region of the visible spectrum.
• Dominant Wavelength (λd):589 nm (typical). This is derived from the CIE chromaticity diagram and represents the single wavelength that best describes the perceived color of the light. For this device, it is very close to the peak wavelength.
• Spectral line half-width (Δλ):20 nm (typical value). This is the width of the emission spectrum at half its maximum power. A value of 20 nm indicates a medium-purity yellow.
• Forward voltage (VF):2.0 V (minimum), 2.4 V (typical), (maximum not specified at 20mA). This is the voltage drop across the LED when operating at the specified current. It is crucial for designing current-limiting circuits.
• Reverse Current (IR):Maximum 10 μA at VR=5V. This is the small leakage current that flows when the specified reverse voltage is applied.

Note on ESD:The datasheet warns that electrostatic discharge and surge may damage the LED. It is strongly recommended to take appropriate electrostatic discharge (ESD) precautions during handling, such as using grounded wrist straps, anti-static gloves, and ensuring all equipment is grounded.

3. Grading System Description

To ensure brightness consistency across different production batches, LEDs are classified based on their luminous intensity measured at the standard test current (20mA). The LTST-S220KSKT uses the following binning code list:

• M Bin:18.0 - 28.0 mcd
• N Bin:28.0 - 45.0 mcd
• P gear:45.0 - 71.0 mcd
• Q grade:71.0 - 112.0 mcd
• R grade:112.0 - 180.0 mcd

Tolerance for each intensity bin is +/- 15%. This means an LED marked as bin N could have an actual intensity ranging from approximately 23.8 mcd to 51.75 mcd. Designers must account for this variation when specifying brightness requirements for their application. The datasheet does not indicate separate binning for wavelength or forward voltage for this specific model, suggesting tighter control or a single-bin specification for these parameters.

4. Performance Curve Analysis

Although the specific charts are not detailed in the provided text, the typical curves for such LEDs include:

• Relative luminous intensity vs. forward current (I-V curve):This curve shows how the light output increases with the forward current. It is typically linear at lower currents but may saturate at higher currents due to thermal effects and efficiency droop.
• Relative luminous intensity vs. ambient temperature:This graph illustrates the derating of light output as ambient (or junction) temperature increases. The output of AlInGaP LEDs typically decreases with rising temperature.
• Forward voltage vs. forward current:This demonstrates the exponential relationship characteristic of a diode. Voltage increases with increasing current.
• Forward Voltage vs. Ambient Temperature:The forward voltage typically has a negative temperature coefficient, meaning it decreases slightly as temperature increases.
• Spectral Distribution:A graph showing the relationship between relative radiant power and wavelength, with a peak near 591 nm and a full width at half maximum of approximately 20 nm.

These curves are crucial for understanding the behavior of the device under non-standard operating conditions and for thermal management design.

5. Mechanical and Packaging Information

5.1 Package Dimensions

This LED complies with the EIA standard SMD package outline. All dimensions are provided in millimeters, with a typical tolerance of ±0.10 mm unless otherwise specified. The datasheet includes detailed dimensional drawings showing the length, width, height, pin pitch, and other key mechanical features required for PCB pad design.

5.2 Pad Design and Polarity

The datasheet provides recommended solder pad dimensions for PCB layout. Following these recommendations ensures reliable solder joints and accurate alignment during the reflow soldering process. The component has polarity markings, typically a notch or a cathode indicator on the package body. Correct orientation is crucial because an LED only allows current to flow in one direction.

5.3 Tape and Reel Packaging

LEDs are supplied on 7-inch diameter reels in industry-standard 8mm tape for compatibility with automated assembly equipment. Key packaging specifications include:

• Empty component pockets are sealed with cover tape.
• Kowane 7-inch reel ya ƙunshi 4000 guda.
• Ƙananan adadin fakitin sauran sassan shine 500 guda.
• Bisa ga ƙayyadaddun reel, an yarda da mafi girman LED 2 da suka ɓace a jere (fanko aljihu).
• Packaging complies with ANSI/EIA 481 specification.

6. Welding and Assembly Guide

6.1 Reflow Soldering Temperature Profile

Provides a recommended infrared (IR) reflow temperature profile for Pb-free soldering processes. The key parameters are:

• Preheating temperature:150–200°C
• Preheating time:Maximum 120 seconds
• Peak Temperature:Maximum 260°C
• Peak Temperature Time:Maximum 10 seconds (and up to two reflow cycles allowed).

This curve is based on JEDEC standards. The datasheet emphasizes that the optimal profile depends on the specific PCB design, components, solder paste, and oven, therefore characterization is required.

6.2 Manual Soldering

If manual soldering is necessary, the following restrictions apply:

• Soldering iron temperature:Maximum 300°C
• Welding time:Maximum 3 seconds (only once).

6.3 Cleaning

Do not use unspecified chemical cleaners as they may damage the LED package. If cleaning is necessary, it is recommended to immerse in ethanol or isopropanol at room temperature for no more than one minute.

6.4 Storage Conditions

• Sealed Packaging:Store at ≤30°C and ≤90% relative humidity (RH). When stored in the original moisture barrier bag with desiccant, the shelf life is one year.
• Opened packaging:The storage environment should not exceed 30°C or 60% RH. LEDs removed from the original packaging should undergo infrared reflow soldering within one week.
• Long-term Storage (Opened):For storage exceeding one week, place the LEDs in a sealed container with desiccant or a nitrogen dry box. LEDs stored outside the packaging for more than one week should be baked at approximately 60°C for at least 20 hours before soldering to remove absorbed moisture and prevent the "popcorn" effect during reflow.

7. Application Suggestions

7.1 Typical Application Scenarios

This side-emitting yellow LED is ideal for applications where PCB top surface space is limited or where the indicator needs to be viewed from the edge. Common uses include:

• Status indicators on consumer electronics (routers, set-top boxes, chargers).
• Backlighting for membrane switches or side-lit panels.
• Dashboard and instrument panel lighting in automotive interiors.
• Industrial equipment status and fault indicator lights.
• Battery level or charging indicator lights in portable devices.

7.2 Design Considerations

• Current Drive:LED is a current-driven device. To ensure uniform brightness, especially when multiple LEDs are connected in parallel, current limiting is crucial. This is typically achieved using a series resistor or a constant current driver circuit. The resistor value can be calculated using the formula: R = (Vcc - VF) / IF, where Vcc is the supply voltage, VF is the LED forward voltage (use the maximum or typical value for safety), and IF is the desired forward current (e.g., 20mA).
• Thermal Management:Although the power consumption is low, maintaining the junction temperature within the limit range is crucial for lifespan and stable light output. If operating at high ambient temperatures or near the maximum current, ensure sufficient PCB copper area or thermal vias.
• ESD Protection:Add ESD protection diodes on sensitive signal lines connected to the LED, or ensure the driving circuit has inherent protection functions, especially if the LED is user-accessible.
• Optical Design:Transparent lenses produce focused beams. If diffuse or wider illumination patterns are required, external diffusers or light guides must be considered in the mechanical design.

8. Technical Comparison and Differentiation

Compared to other yellow indicator LEDs, the key differentiation of the LTST-S220KSKT lies in:

• Side-view package:Unlike top-emitting LEDs, this form factor saves vertical space and enables unique lighting geometry, which is a distinct mechanical advantage.
• AlInGaP Technology:Compared to older gallium phosphide (GaP)-based yellow LEDs, it offers higher efficiency and better temperature stability, resulting in brighter and more consistent output.
• Full Process Compatibility:Its design for tape and reel packaging, automated placement, and infrared reflow soldering makes it the preferred choice for cost-effective, high-volume, automated manufacturing.
• RoHS Compliance:It meets modern environmental standards, which are mandatory requirements in many markets.

9. Frequently Asked Questions (Based on Technical Parameters)

Q1: For a 5V power supply, what size resistor do I need?
A: Using a typical forward voltage (VF) of 2.4V and a target current (IF) of 20mA, the series resistor value is R = (5V - 2.4V) / 0.02A = 130 ohms. A standard 130Ω or 150Ω resistor is suitable. Always verify the actual brightness and consider using the maximum VF for a more conservative design.

Q2: Can I drive this LED with a 3.3V microcontroller pin?
A: Iya, amma ƙarfin ƙarfin wutar lantarki da ake da shi kaɗan ne. VF_min shine 2.0V, VF_typ shine 2.4V. A 3.3V, lissafin resistor ya zama R = (3.3V - 2.4V) / 0.02A = 45 ohms. Wannan yana yiwuwa, amma canje-canjen VF da ƙarfin wutar lantarki na iya haifar da canje-canje masu mahimmanci a cikin halin yanzu. Don aikace-aikace masu mahimmanci, ana ba da shawarar amfani da direban halin yanzu na dindindin ko yin bincike mai zurfi.

Q3: Me yasa kusurwar gani ta yi fadi (130°)?
A: An tsara kunshe na gefe da ƙirar ruwan tabarau mai haske don inganta fitar da haske a cikin faɗin yanki mai kama da kwalliya. Wannan yana da amfani ga alamun nuni waɗanda ke buƙatar ganuwa daga kusurwoyi daban-daban ba tare da ruwan tabarau mai watsawa ba.

Q4: Yadda ake fassara lambar rarrabuwa akan odar (misali N)?
A: Lambar rarrabuwa ta tsara yankin tabbacin ƙarfin haske. Yin odar matakin N yana tabbatar da cewa LED ɗin da kuka karɓa zai kasance tsakanin 28.0 zuwa 45.0 mcd a 20mA. Don aikace-aikacen da ke buƙatar mafi ƙarancin haske, ku ƙayyade matakin da ya dace ko ku tuntubi samarwa na mai siyarwa.

10. Practical Application Cases

Scenario: Designing status indicator lights for a network router.
The designer required a power/activity indicator visible from the slim front face of the router. The PCB is mounted vertically, so a side-emitting LED was the ideal choice. They placed the LTST-S220KSKT at the edge of the PCB, facing a light guide that directs the light to a small window on the router's panel. They used a 47Ω series resistor to drive it from the 3.3V system power rail, resulting in a current of approximately 19mA ((3.3V-2.4V)/47Ω). They selected the P-bin LED to ensure sufficient brightness was visible after passing through the light guide. The design utilizes the automatic pick-and-place and reflow processes specified in the datasheet, ensuring reliable and fast assembly.

11. Introduction to Principles

Light-emitting diode (LED) is a semiconductor device that emits light when an electric current passes through it. This phenomenon is called electroluminescence. In the LTST-S220KSKT, the active region is made of aluminum indium gallium phosphide (AlInGaP). When a forward voltage is applied, electrons from the n-type semiconductor and holes from the p-type semiconductor are injected into the active region. When an electron recombines with a hole, it transitions from a higher energy state to a lower one, releasing energy in the form of a photon (light particle). The specific composition of the AlInGaP alloy determines the bandgap energy, which in turn determines the wavelength (color) of the emitted light—in this case, yellow (approximately 589-591 nm). The side-view package contains a reflective cavity and a molded epoxy lens to direct the generated light laterally out of the package.

12. Development Trends

The development trends for SMD indicator LEDs like these continue to progress in several key areas:

• Efficiency Enhancement:Ongoing improvements in materials science aim to achieve higher lumens per watt (luminous efficacy), reducing power consumption at the same brightness level.
• Miniaturization:Package size continues to shrink (e.g., from 0603 to 0402 metric), while maintaining or improving optical performance, enabling denser PCB designs.
• Higher Reliability and Stability:Improvements in packaging materials and die-attach technology enhance lifespan and color stability over time and temperature.
• Wurin launi mai faɗi da daidaito:Ƙa'idodin matakan tsayin daka da ƙarfi suna zama ma'auni, suna ba masu ƙira aikin da ake iya hasashewa.
• Haɗaɗɗiyar:The trend of integrating multiple LEDs (e.g., RGB), control ICs, and even passive components into a single, smarter modular package is growing.

Components like the LTST-S220KSKT represent a mature, highly optimized solution in this evolving field, balancing performance, cost, and manufacturability.