LTW-S225DSKS-PH SMD LED Datasheet - Side-View Dual-Color (White/Yellow) LED - Package Dimensions - Voltage 2.5-3.7V/1.6-2.4V - Power 72/62.5mW - Technical Documentation

1. Product Overview

Bu belge, yan yayımlı çift renkli yüzey montaj cihazı (SMD) LED'i olan LTW-S225DSKS-PH'nin tam teknik özelliklerini sağlar. Bu bileşen, otomatik montaj süreçleri için tasarlanmış kompakt bir paket içinde iki farklı ışık yayan çip entegre eder. Ana uygulama alanı, güvenilir durum göstergesi veya arka aydınlatma işlevi gerektiren, alanı kısıtlı elektronik cihazlardır.

1.1 Core Features and Target Market

The LTW-S225DSKS-PH design incorporates several key features that make it suitable for modern electronics manufacturing. It complies with the RoHS (Restriction of Hazardous Substances) directive, ensuring adherence to environmental regulations. The device utilizes a tin-plated lead frame to enhance solderability. It integrates ultra-high brightness semiconductor chips: one based on InGaN technology for white light emission, and another based on AlInGaP technology for yellow light emission.

The package is supplied in a standard 8mm carrier tape format, wound on a 7-inch diameter reel, conforming to EIA (Electronic Industries Alliance) standards, which facilitates compatibility with high-speed automated pick-and-place equipment commonly used in high-volume production. The device is also designed to be compatible with infrared (IR) reflow soldering processes, a standard process for lead-free (Pb-free) PCB assembly.

Its primary target applications encompass telecommunications equipment (e.g., cellular and cordless phones), office automation equipment (e.g., notebook PCs), network systems, various home appliances, and indoor signage or display applications. Specific uses include keyboard backlighting, power, connection, or system status indicators, miniature displays, and general signal or symbol illumination.

2. Technical Parameters: An In-Depth and Objective Analysis

LTW-S225DSKS-PH nia fekhete e vepruar nga nje grup i plote i parametrave elektrik, optik dhe termik te matur ne kushte standarde (perveç nese specifikohet ndryshe, Ta=25°C). Kuptimi i ketyre parametrave eshte thelbesor per projektimin e sakte te qarkut dhe funksionimin e besueshem.

2.1 Absolute Maximum Ratings

Keto vlera percaktimin kufijt e stresit qe mund te shkaktojne demtim te perhershem te pajisjes. Funksionimi ne ose mbi kete kufi nuk garanton besueshmeri dhe duhet te shmanget per te siguruar performancen afatgjate.

• Power Dissipation (Pd):The white light chip is 72 mW, and the yellow light chip is 62.5 mW. This is the maximum power that the LED can dissipate as heat.
• Peak Forward Current (I_FP):White light is 100 mA, yellow light is 60 mA. This is the maximum instantaneous current allowed under pulse conditions (1/10 duty cycle, 0.1ms pulse width).
• Direct Current (I_F):White light is 20 mA, yellow light is 25 mA. This is the maximum continuous forward current recommended for normal operation.
• Operating temperature range:-20°C to +80°C. This is the ambient temperature range over which the LED is designed to operate.
• Storage temperature range:-30°C to +85°C. This is the storage temperature range when the device is not powered.
• Infrared Soldering Conditions:Withstands 260°C for 10 seconds, which is a typical lead-free reflow soldering temperature profile.

2.2 Electrical and Optical Characteristics

These are typical performance parameters measured at the standard test current I_F= 20mA.

• Luminous intensity (I_V):For white LEDs, the intensity ranges from a minimum of 112.0 mcd to a maximum of 450.0 mcd. For yellow LEDs, the range is from 45.0 mcd to 180.0 mcd. The actual measured value of a specific unit depends on its binning grade (see Section 4). Measurement uses a sensor corrected with a filter to approximate the CIE photopic response curve.
• Viewing Angle (2θ_1/2):The viewing angle is typically 130 degrees for both colors. This is the full angle at which the luminous intensity is half of the value measured on the central axis (0°). Such a wide viewing angle is characteristic of side-view LEDs.
• Dominant Wavelength (λ_d):Applicable only to yellow LEDs, ranging from 584.0 nm to 596.0 nm. This is the single wavelength perceived by the human eye that defines the color.
• Peak Emission Wavelength (λ_P):Typically 591.0 nm for yellow LEDs, representing the peak of its spectral power distribution.
• Chromaticity Coordinates (x, y):For white LEDs, typical coordinates are x=0.31, y=0.31, placing them in the "cool white" region of the CIE 1931 chromaticity diagram. The color of yellow LEDs is defined by their dominant wavelength bin.
• Spectral line half-width (Δλ):For yellow LEDs, it is typically 15 nm, indicating the spectral purity or bandwidth of the emitted light.
• Forward Voltage (V_F):White LED: minimum 2.5V, maximum 3.7V. Yellow LED: minimum 1.6V, maximum 2.4V. This is the voltage drop across the LED at a 20mA drive current. The difference in V_Fbetween the two colors is significant and must be considered in circuit design, especially if they are to be driven by the same current source.
• Reverse Current (I_R):at Reverse Voltage (V_RWhen the voltage is 5V, the maximum reverse current for both colors is 10.0 μA.Important Notice:The datasheet clearly states that the reverse voltage condition is only for infrared (IR) testing; this device is not designed for reverse operation. Applying reverse bias in application circuits is not recommended.

2.3 Thermal Considerations

The power dissipation ratings (72mW/62.5mW) are directly related to thermal management. Exceeding these limits increases the junction temperature, leading to accelerated luminous flux depreciation (light output decline over time), chromaticity coordinate shift, and ultimately device failure. The operating temperature range of -20°C to +80°C defines the ambient conditions. Designers must ensure that the combined effect of ambient temperature and self-heating from power dissipation keeps the LED's junction temperature within safe limits.

3. Grading System Description

To ensure consistency in mass production, LEDs are sorted into different "bins" based on key performance parameters. The LTW-S225DSKS-PH utilizes a multi-dimensional binning system.

3.1 Luminous Intensity (I_V) Binning

LEDs are classified based on their light output measured at 20mA.

White LED binning:

• R bin:112.0 – 180.0 mcd
• S gear:180.0 – 280.0 mcd
• T gear:280.0 – 450.0 mcd

Tolerance within each bin is +/- 15%.

Yellow LED binning:

• P grade:45.0 – 71.0 mcd
• Q grade:71.0 – 112.0 mcd
• R bin:112.0 – 180.0 mcd

Tolerance within each bin is +/- 15%.

3.2 Hue / Chromaticity Binning

For white LEDs, color consistency is managed by binning the chromaticity coordinates (x, y) defined by specific quadrilaterals on the CIE 1931 diagram (e.g., S1-1, S1-2, S2-1, etc.). The tolerance for each hue bin is +/- 0.01 on both the x and y coordinates. For yellow LEDs, a simpler dominant wavelength binning is used:

• H Bin:584.0 – 590.0 nm
• J band:590.0 – 596.0 nm

The tolerance for each wavelength bin is +/- 1 nm.

This binning system allows designers to select devices that meet the specific brightness and color consistency requirements of their application, which is crucial for applications where uniformity is important, such as multi-LED backlights or status indicator arrays.

4. Performance Curve Analysis

Although the provided text does not fully detail specific graphs, the typical curves for such LEDs will include the following, measured at an ambient temperature of 25°C unless otherwise noted:

4.1 Current-Voltage (I-V) Curve

This graph shows the forward current (I_F) and forward voltage (V_F) relationship. It is nonlinear, exhibiting diode characteristics. The curve for AlInGaP (yellow light) chips typically has a lower knee voltage (approximately 1.8V) compared to InGaN (white light) chips (approximately 3.0V). This curve is crucial for designing current-limiting circuits, whether using a simple resistor or a constant current driver.

4.2 Relationship Between Relative Luminous Intensity and Forward Current

This graph illustrates how light output increases with drive current. It is typically linear within a certain range but saturates at higher currents due to efficiency droop and thermal effects. Operation near or exceeding the absolute maximum DC current (20/25mA) is not recommended, as it reduces efficiency and lifespan.

4.3 Relationship between Relative Luminous Intensity and Ambient Temperature

LED light output decreases as junction temperature increases. This curve quantifies that relationship. For AlInGaP LEDs (yellow), the reduction is typically more pronounced than for InGaN LEDs (white). This is a key consideration for applications with high ambient temperatures or poor PCB thermal management.

4.4 Spectral Distribution

For the yellow AlInGaP LED, this will show a relatively narrow peak centered at 591 nm. For the white InGaN LED, the spectrum is much broader, composed of light emitted from the blue InGaN chip combined with light from the phosphor layer, thereby forming a continuous spectrum across the visible wavelength range.

5. Mechanical and Packaging Information

5.1 Package Dimensions and Pin Definitions

LTW-S225DSKS-PH is a side-view SMD package. Key dimension notes: All dimensions are in millimeters, with a standard tolerance of ±0.1 mm unless otherwise specified. Pin definition is crucial for correct orientation:

• Pins 1 and 2 are assigned to the AlInGaP yellow LED chip.
• Pins 3 and 4 are assigned to the InGaN white light chip.

The physical layout ensures that the primary light emission comes from the side of the package, not the top.

5.2 Recommended PCB Pad Design and Polarity

The datasheet includes a schematic diagram of the recommended pad layout on the printed circuit board. Following this design helps achieve reliable soldering, correct alignment, and good mechanical strength. The pad pattern also provides necessary heat dissipation and solder volume. Polarity is indicated by the pin number; correctly connecting the anode and cathode is crucial. Applying reverse voltage may damage the LED.

6. Soldering and Assembly Guide

6.1 Infrared Reflow Soldering Process

This device is compatible with infrared (IR) reflow soldering, which is the standard process for lead-free assembly. The maximum rated condition is 260°C for 10 seconds. In practice, a standard lead-free reflow temperature profile should be used, with a peak temperature between 240°C and 260°C and a time above liquidus (TAL) suitable for the solder paste used. The recommended profile in the datasheet should be followed to avoid thermal shock or damage to the LED package or internal bond wires.

6.2 Cleaning

Post-soldering cleaning must be performed with care. Only specified chemicals should be used. The datasheet recommends that if cleaning is required, immersion in ethanol or isopropanol at room temperature for no more than one minute is acceptable. Using unspecified or corrosive chemical liquids may damage the LED's epoxy lens or packaging material, leading to reduced light output or premature failure.

6.3 Storage and Operation

Electrostatic Discharge (ESD) Precautions:LEDs are sensitive to electrostatic discharge and voltage surges. It is recommended to use a wrist strap or anti-static gloves during operation. All equipment and workbenches must be properly grounded.

Moisture Sensitivity:LED e wa a kewaye a cikin jakar hana danshi tare da maganin bushewa. A cikin yanayin rufewa, ya kamata a adana shi a ƙarƙashin yanayin zafi na 30°C ko ƙasa da haka, da danshi na kusan (RH) 90% ko ƙasa da haka, ana ba da shawarar tsawon lokacin ajiyar shekara guda. Da zarar an buɗe fakitin asali, yanayin ajiyar bai kamata ya wuce 30°C ko 60% RH ba. Abubuwan da aka ciro daga fakitin bushewa ya kamata a yi musu haɗin infrared reflow a cikin mako guda (matakin hankali na danshi 3, MSL-3). Idan ana buƙatar ajiyar dogon lokaci a waje da jakar asali, ya kamata a adana su a cikin akwati mai rufi tare da maganin bushewa. Idan an buɗe ajiyar sama da mako guda, kafin haɗawa yana buƙatar gasa a kusan 60°C na aƙalla sa'o'i 20, don hana "popcorn" yanayin yayin reflow.

7. Packaging and Ordering Information

7.1 Carrier Tape and Reel Specifications

LTW-S225DSKS-PH is provided in the industry-standard 8mm wide embossed carrier tape format, wound onto a 7-inch (178mm) diameter reel. Each reel contains 4000 pieces. The carrier tape pockets are sealed with a top cover tape to protect the components during transportation and handling. The packaging complies with the ANSI/EIA-481 specification. For quantities less than a full reel, the minimum packaging quantity for the remainder is specified as 500 pieces. The carrier tape design allows for a maximum of two consecutive missing components (empty pockets).

8. Application Suggestions and Design Considerations

8.1 Typical Application Circuit

Due to differences in forward voltage characteristics, each color chip inside the LTW-S225DSKS-PH must be driven independently. The simplest driving method is to use a series current-limiting resistor for each chip. The formula for calculating the resistor value is R = (V_{Power Supply}- V_F) / I_F, where I_Fis the required drive current (e.g., 20mA), V_Fis the typical or maximum forward voltage from the datasheet, depending on the design margin. For better consistency and stability, especially with temperature or supply voltage variations, a constant current drive circuit is recommended.

8.2 Thermal Management in Design

Although SMD LEDs are small in size, effective thermal management is crucial for performance and lifespan. The PCB acts as the primary heat sink. Using the recommended pad design and connecting sufficient copper area to the LED's thermal pad helps dissipate heat. For high-power or high ambient temperature applications, it may be necessary to add thermal vias or larger copper foil areas under the package to transfer heat away from the LED junction.

8.3 Optical Design Considerations

As a side-emitting LED, its primary light emission direction is parallel to the PCB surface. This is ideal for edge-lit light guide plates, illuminating side-firing indicator lights, or providing backlighting for keys from the side. When designing light pipes, lenses, or diffusers, designers should consider the 130-degree viewing angle to ensure uniform illumination and the desired visual effect.

9. Technical Comparison and Differentiation

The key differentiating factor of the LTW-S225DSKS-PH is its dual-color, side-emitting configuration within a single SMD package. Compared to using two separate side-emitting LEDs, this saves PCB space. The use of AlInGaP material for yellow light provides high efficiency and good color purity, while the InGaN-based white light offers a modern cool white source. The combination of a 130-degree wide viewing angle with compatibility for automated assembly and reflow processes makes it a versatile and cost-effective choice for high-volume manufacturing.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive the white and yellow light chips using the same current-limiting resistor?
A: E le mafai. Ona o le eseesega tele o le voltage i luma (i le 20mA, e tusa ma le 3.2V mo le malamalama pa'epa'e, 2.0V mo le samasama), o le fa'apipi'i fa'atasi i se tete'e e tasi o le a mafua ai le le paleni o le alavai, e ono fa'atosina ai le tasi chip ae le lava le fa'aogaina o le isi. E mana'omia e chip ta'itasi se pulea fa'atasi o le alavai._FF: O le a le uiga o le fa'ailoga fa'avasegaina o le malosi o le malamalama (fa'ata'ita'iga R, S, T)?

A: O le fa'ailoga fa'avasegaina e fa'ailoa mai ai le va'aiga o le gaosiga o le malamalama e fa'amautinoa e lena LED fa'apitoa i lalo o le su'ega masani o le alavai (20mA). Mo se fa'ata'ita'iga, o le LED pa'epa'e mai le vasega T (280-450 mcd) e sili atu lona malamalama nai lo le mai le vasega R (112-180 mcd). E fa'ailoa mai e le au mamanu le vasega mana'omia e fa'amautinoa ai le tutusa o le malamalama o a latou oloa.
F: E talafeagai lenei LED mo fa'aoga i fafo?

A: The datasheet specifies an operating temperature range of -20°C to +80°C and lists typical indoor applications. For outdoor use, factors such as wider temperature extremes, epoxy degradation from UV exposure, and moisture ingress must be evaluated. The device is not specifically rated for harsh environments.
Q: How critical is the one-week timeframe for completing reflow soldering after opening the moisture barrier bag?

A: This is very important for reliability. If an MSL-3 rated component absorbs excessive moisture from the atmosphere and is then subjected to the high temperatures of reflow soldering, the rapid vaporization of the moisture can cause internal delamination or cracking ("popcorning"), leading to immediate or latent failure. If the timeframe is exceeded, follow the baking guidelines.
11. Practical Application Examples

Example 1: Mobile Device Status Indicator:

A single LTW-S225DSKS-PH can provide multiple status indications. The white LED can indicate "Power On" or "Fully Charged," while the yellow LED can indicate "Charging" or "Low Battery." The side-emitting characteristic allows light to be coupled into a light guide that extends to the edge of the device housing, creating a clean indicator.Example 2: Industrial Control Panel Backlighting:

A series of such LEDs can be placed along the edge of a membrane switch panel. White LEDs provide general backlighting for all keys under low-light conditions. Yellow LEDs can be connected to specific function keys (e.g., Emergency Stop, Warning), providing a striking, attention-grabbing color when activated, all using the same compact component footprint.12. Introduction to Working Principles

A light-emitting diode (LED) is a semiconductor device that emits light through electroluminescence. When a forward voltage is applied across the p-n junction, electrons and holes recombine, releasing energy in the form of photons. The color of the light is determined by the energy band gap of the semiconductor material.

AlInGaP (Aluminium Indium Gallium Phosphide):

• Mfumo huu wa nyenzo hutumiwa kwa LED ya mwanga wa manjano. Pengo lake la bendi ya nishati linalingana na utoaji wa mwanga katika maeneo ya mwanga nyekundu, machungwa, kahawia na manjano ya wigo. Inajulikana kwa ufanisi wake wa juu katika rangi hizi.InGaN (Indium Gallium Nitride):
• This material system is used for white LEDs. Typically, a blue-emitting InGaN chip is combined with a phosphor coating. The blue light from the chip excites the phosphor, which then re-emits light over a broader spectrum, creating the perception of white light. The specific phosphor blend determines the white point (e.g., cool white, warm white).The side-view package structure uses a reflective cavity and a molded epoxy lens to direct the primary light output to the side of the component body.

13. Technology Trends

The optoelectronics industry continues to advance in several key areas related to components such as the LTW-S225DSKS-PH. The industry is constantly pursuing

higher luminous efficacy(more light output per watt of electrical input), which improves energy efficiency and allows for the use of lower drive currents or the attainment of brighter output.Improved color renderingand a wider selection of white points (CCT - correlated color temperature) are trends, especially for white LEDs.MiniaturizationContinuous development allows for smaller package sizes while maintaining the same or better performance. Additionally,Enhanced reliability and lifespan under higher temperature and humidity conditionsIt is an ongoing development goal, which expands the potential application environments for SMD LEDs. Integrating multiple functions (such as multiple colors or even integrated drivers) into a single package also represents a significant trend in component design.Under higher temperature and humidity conditions are ongoing development goals, expanding the potential application environments for SMD LEDs. The integration of multiple functions (like multiple colors or even integrated drivers) into single packages also represents a significant trend in component design.