LTST-C281KSKT Yellow SMD LED Datasheet - 0.35mm Height - 2.4V Typ - 75mW - English Technical Documentation

1. Product Overview

The LTST-C281KSKT is an ultra-thin, surface-mount chip LED designed for modern electronic applications requiring minimal vertical profile. This device utilizes an AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material to produce a bright yellow light output. Its primary design goals are compatibility with automated assembly processes, adherence to environmental regulations, and reliable performance in a compact form factor.

The core advantage of this LED lies in its exceptionally low profile of 0.35mm, making it suitable for applications where space constraints are critical, such as in ultra-thin displays, backlighting for slim consumer electronics, and indicator lights in densely packed PCBs. It is packaged on 8mm tape and supplied on 7-inch diameter reels, facilitating high-speed pick-and-place manufacturing.

2. Technical Parameter Deep Dive

2.1 Absolute Maximum Ratings

The device's operational limits are defined under an ambient temperature (Ta) of 25°C. Exceeding these ratings may cause permanent damage.

• Power Dissipation (Pd): 75 mW. This is the maximum amount of power the LED can dissipate as heat without degradation.
• Peak Forward Current (I_F(PEAK)): 80 mA. Wannan yana yiwuwa ne kawai a ƙarƙashin yanayin bugun jini (1/10 aikin aiki, 0.1ms faɗin bugun jini) don hana zafi.
• Ci gaba da Ci gaba na Gaba (I_F): 30 mA DC. Wannan shine matsakaicin shawarar da aka ba da shawara don ci gaba da aiki.
• Juyawa Voltage (V_R): 5 V. Yin amfani da juyawar wutar lantarki fiye da wannan iyaka na iya rushe PN junction na LED.
• Operating Temperature Range: -30°C to +85°C. The device is guaranteed to function within this ambient temperature range.
• Storage Temperature Range: -40°C to +85°C.
• Infrared Reflow Soldering Condition: Withstands a peak temperature of 260°C for a maximum of 10 seconds, compatible with standard Pb-free (lead-free) soldering processes.

2.2 Electro-Optical Characteristics

Key performance parameters are measured at Ta=25°C and a standard test current of I_F = 20mA.

• Luminous Intensity (I_V): Ranges from a minimum of 28.0 mcd to a maximum of 180.0 mcd. The typical value falls within this wide binning range (see Section 3). Measurement is performed using a sensor filtered to match the CIE photopic eye-response curve.
• Viewing Angle (2θ_1/2): 130 degrees. This is the full angle at which the luminous intensity drops to half of its value measured on-axis. It indicates a wide, diffuse light emission pattern suitable for area illumination or wide-angle indicators.
• Peak Emission Wavelength (λ_P): 588 nm. This is the wavelength at which the spectral power distribution reaches its maximum.
• Dominant Wavelength (λ_d): 587 nm to 597 nm. This is the single wavelength perceived by the human eye that defines the color (yellow) of the LED, derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): 15 nm. This parameter describes the spectral purity or bandwidth of the emitted light, measured at half the maximum intensity.
• Forward Voltage (V_F): Typical value is 2.4V, with a range from 2.0V to the maximum specified. This is the voltage drop across the LED when conducting 20mA.
• Reverse Current (I_R): Maximum of 10 μA when a reverse bias of 5V is applied.

3. Binning System Explanation

To ensure color and brightness consistency in production, LEDs are sorted into bins based on key parameters. The LTST-C281KSKT uses a three-code binning system (e.g., D4-P-K).

3.1 Forward Voltage Binning

Bins ensure LEDs in a circuit have similar voltage drops, preventing current imbalance in parallel configurations.

• Bin D2: V_F = 1.80V - 2.00V @20mA
• Bin D3: V_F = 2.00V - 2.20V @20mA
• Bin D4: V_F = 2.20V - 2.40V @20mA
• Tolerance per bin: ±0.1V

3.2 Luminous Intensity Binning

This groups LEDs by their light output brightness.

• Bin N: I_V = 28.0 mcd - 45.0 mcd @20mA
• Bin P: I_V = 45.0 mcd - 71.0 mcd @20mA
• Bin Q: I_V = 71.0 mcd - 112.0 mcd @20mA
• Bin R: I_V = 112.0 mcd - 180.0 mcd @20mA
• Tolerance per bin: ±15%

3.3 Dominant Wavelength Binning

Critical for color-matched applications, this defines the precise shade of yellow.

• Bin J: λ_d = 587.00 nm - 589.50 nm @20mA
• Bin K: λ_d = 589.50 nm - 592.00 nm @20mA
• Bin L: λ_d = 592.00 nm - 594.50 nm @20mA
• Bin M: λ_d = 594.50 nm - 597.00 nm @20mA
• Tolerance per bin: ±1 nm

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (Fig.1, Fig.6), their implications are standard for AlInGaP LEDs.

• I-V (Current-Voltage) Curve: Exhibits the typical exponential relationship of a diode. The forward voltage shows a positive temperature coefficient, meaning V_F decreases slightly as junction temperature increases for a given current.
• Luminous Intensity vs. Forward Current: Intensity is approximately proportional to forward current in the normal operating range (up to 30mA). Driving beyond this point leads to sub-linear increases due to efficiency droop and increased thermal effects.
• Luminous Intensity vs. Ambient Temperature: The light output of AlInGaP LEDs generally decreases as ambient (and junction) temperature rises. This thermal derating must be considered in high-temperature environments.
• Spectral Distribution: The emission spectrum is centered around 588nm (yellow) with a relatively narrow half-width of 15nm, indicating good color saturation.
• Viewing Angle Pattern: The 130-degree viewing angle suggests a near-Lambertian emission pattern, where intensity is roughly cosine-dependent on the viewing angle off-axis.

5. Mechanical and Packaging Information

5.1 Package Dimensions and Polarity

The device conforms to an EIA standard package outline. Key dimensional features include the overall height of 0.35mm. The package incorporates a water-clear lens. Polarity is indicated by a cathode mark, typically a notch, green dot, or other visual indicator on the package or tape. The exact marking should be verified from the package drawing.

5.2 Recommended Solder Pad Layout

A land pattern (solder pad footprint) is provided to ensure reliable solder joint formation during reflow. This pattern is designed to facilitate proper solder wetting, self-alignment of the component during reflow, and long-term mechanical reliability. Adhering to this recommended layout is crucial to prevent tombstoning or poor solder connections.

5.3 Tape and Reel Specifications

The LEDs are supplied in embossed carrier tape with a protective cover tape, wound on 7-inch (178mm) diameter reels.

• Pocket Pitch: 8mm (standard for many small SMD components).
• Quantity per Reel: 5000 pieces.
• Minimum Order Quantity (MOQ) for remnants: 500 pieces.
• Missing Components: A maximum of two consecutive empty pockets is allowed.
• Standard: Packaging complies with ANSI/EIA-481 specifications.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

A suggested infrared (IR) reflow profile is provided for Pb-free solder processes. Key parameters include:

• Preheating: 150°C to 200°C.
• Preheat Time: Maximum 120 seconds to allow for uniform heating and solvent evaporation from solder paste.
• Peak Temperature: Maximum 260°C.
• Time Above Liquidus (TAL): The duration within 5°C of the peak temperature should be limited to a maximum of 10 seconds. The component can withstand this peak temperature for a maximum of two reflow cycles.

The profile is based on JEDEC standards. Engineers must characterize the profile for their specific PCB design, solder paste, and oven to create reliable solder joints.

6.2 Hand Soldering

If manual soldering is necessary, extreme care must be taken:

• Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per lead.
• Limit: Only one hand-soldering cycle is permitted to avoid thermal damage to the plastic package and the semiconductor die.

6.3 Cleaning

Cleaning is generally not required after reflow with no-clean solder paste. If cleaning is necessary (e.g., after hand soldering with flux):

• Abubuwan narkewa da aka ba da shawarar: Yi amfani da kawai masu tsaftacewa na barasa kamar ethyl alcohol ko isopropyl alcohol (IPA).
• Tsari: Immerse the LED at normal room temperature for less than one minute. Agitation may be used gently.
• Avoid: Do not use unspecified chemical liquids, ultrasonic cleaning (can cause mechanical stress), or harsh solvents that may damage the epoxy lens or package markings.

7. Storage and Handling

7.1 Moisture Sensitivity

The LED package is moisture-sensitive. Adherence to storage conditions is critical to prevent "popcorning" (package cracking) during reflow due to rapid vaporization of absorbed moisture.

• Sealed Bag (Original Packaging): Store at ≤30°C and ≤90% Relative Humidity (RH). Shelf life e one year when stored in moisture-proof bag with desiccant.
• After Bag Opening: The exposure time out of the bag is limited. The recommended "floor life" before reflow is 672 hours (28 days) when stored at ≤30°C and ≤60% RH.
• Extended Storage (Opened): For storage beyond 672 hours, place components in a sealed container with desiccant or in a nitrogen desiccator.
• Rebaking: Components exposed for more than 672 hours must be baked at approximately 60°C for at least 20 hours before soldering to remove absorbed moisture.

7.2 Electrostatic Discharge (ESD) Protection

LEDs are susceptible to damage from electrostatic discharge. Precautions must be taken during all handling and assembly stages.

• Operators should wear a grounded wrist strap or anti-static gloves.
• All workstations, tools, and equipment must be properly grounded.
• Use conductive or dissipative mats on work surfaces.
• Transport and store components in ESD-protective packaging.

8. Application Suggestions

8.1 Typical Application Scenarios

• Status Indicators: Power, connectivity, and function status lights in consumer electronics (routers, set-top boxes, smart home devices), office equipment, and industrial control panels.
• Backlighting: Edge-lit or direct backlighting for LCD displays in thin devices, keypad illumination, and icon backlighting where height is constrained.
• Automotive Interior Lighting: Dashboard indicators, switch illumination, and ambient lighting (subject to verification of specific automotive-grade requirements).
• Portable and Wearable Devices: Battery level indicators, notification lights in smartphones, tablets, and fitness trackers benefiting from the ultra-low profile.

8.2 Design Considerations

• Current Limiting: Always use a series current-limiting resistor or a constant-current driver. Calculate the resistor value using R = (V_supply - V_F) / I_FDo not connect directly to a voltage source.
• Thermal Management: Although power dissipation is low, ensure adequate PCB copper area or thermal vias under the solder pads to conduct heat away, especially when operating near maximum current or in high ambient temperatures. This maintains luminous output and longevity.
• Parallel Connections: Avoid connecting multiple LEDs directly in parallel from a single voltage source. Slight variations in V_F can cause significant current imbalance, with one LED hogging most of the current. Use separate current-limiting resistors for each LED or a constant-current driver with multiple channels.
• Optical Design: The wide 130-degree viewing angle provides good off-axis visibility. For focused light, external lenses or light guides may be required.

9. Technical Comparison and Differentiation

The LTST-C281KSKT offers specific advantages in its class:

• vs. Standard Thickness LEDs (0.6mm+): The primary differentiator is the 0.35mm height, enabling design in space-critical applications where traditional LEDs cannot fit.
• vs. Other Yellow LED Technologies: The use of AlInGaP semiconductor material, compared to older technologies like GaAsP, provides higher luminous efficiency (more light output per unit of electrical power), better temperature stability, and superior color purity (narrower spectrum).
• vs. Non-Reel Packaged LEDs: The 8mm tape-on-reel packaging is a significant advantage for mass production, ensuring compatibility with high-speed automated pick-and-place machines, reducing assembly time and cost.
• Compliance: It meets RoHS (Restriction of Hazardous Substances) directives and is classified as a Green Product, which is a mandatory requirement for electronics sold in many global markets.

10. Frequently Asked Questions (FAQ)

10.1 Menene bambanci tsakanin Peak Wavelength da Dominant Wavelength?

Peak Wavelength (λ_P): Tsayin raƙuman zahiri, na zahiri wanda LED ke fitar da mafi girman ƙarfin haske. Ana auna shi kai tsaye daga bakan.
Dominant Wavelength (λ_d): Ƙimar da aka ƙididdige bisa ga fahimtar launi na ɗan adam (taswirar CIE). Shi ne tsayin raƙuman haske guda ɗaya wanda zai yi kama da launi ɗaya da fitowar bakan LED mai faɗi. Don ma'anar launi da daidaitawa, dominant wavelength shine mafi dacewa.

10.2 Shin zan iya sarrafa wannan LED a 30mA a kai a kai?

Yes, 30mA is the maximum rated DC forward current. However, for optimal longevity and to account for real-world conditions like elevated ambient temperature, it is considered good engineering practice to derate this value. Operating at 20mA (the standard test condition) or lower will significantly extend the LED's operational life and maintain more stable light output.

10.3 Why is binning important, and which bin should I choose?

Binning yana da mahimmanci don daidaiton bayyanar da aiki a cikin aikace-aikace. Misali, a cikin rukunin fitilun LED na yanayi da yawa, amfani da LED daga nau'ikan ƙarfi ko tsawon raƙuman ruwa daban-daban zai haifar da bambance-bambancen haske da launuka a bayyane.
Zaɓi bins bisa ga bukatun aikace-aikacenku: Don daidaitawar launi mai matsi (misali, rawaya na musamman na alama), ƙayyade ƙunshin tsawon raƙuman ruwa mai rinjaye (J, K, L, ko M). Don daidaiton haske a cikin raka'a da yawa, ƙayyade ƙunshin ƙarfin haske (N, P, Q, ko R). Don daidaita halin yanzu a cikin layukan layi, ƙayyade ƙunshin ƙarfin lantarki na gaba (D2, D3, D4).

10.4 Is a heat sink required?

Ba a yawanci buƙatar mai sanyaya zafi na musamman don LED guda ɗaya da ke aiki a ko ƙasa da 30mA saboda ƙarancin watsawar wutar lantarki na 75mW. Duk da haka, ingantaccen sarrafa zafi a matakin PCB yana da mahimmanci. Wannan yana nufin samar da isasshen yanki na tagulla (kushin zafi) da aka haɗa zuwa kushin solder na LED don kai zafi cikin kayan PCB, wanda ke aiki azaman mai yada zafi. Wannan yana da mahimmanci musamman ga jerin LED ko aiki a cikin yanayin zafi mai girma.

11. Practical Design Case Study

Scenario: Designing a low-battery indicator for a handheld medical device. The device housing has an internal height limitation of 0.5mm for the PCB and all components in the indicator area.
Challenge: A standard LED with 0.6mm height would not fit.
Solution: LTST-C281KSKT, tare da tsawon 0.35mm, an zaɓe shi. Ana ƙididdige resistor mai iyakancewar halin yanzu don wadata 3.3V: R = (3.3V - 2.4V) / 0.020A = 45Ω. An zaɓi resistor na ƙima na 47Ω, wanda ya haifar da I_F ≈ 19mA. Faɗin kusurwar kallo na digiri 130 yana tabbatar da cewa ana iya ganin mai nuna alama daga kusurwoyi daban-daban. An zaɓi launin rawaya azaman mai nuna gargaɗi/gargadi na duniya. Kayan kunnawa na tef da reel yana ba da damar haɗawa ta atomatik, yana tabbatar da ingantaccen masana'antu da aminci.

12. Technology Principle Introduction

LTST-C281KSKT yana dogara ne akan fasahar semiconductor na AlInGaP. Wannan kayan aiki shine semiconductor mai hadawa daga rukunin III-V. Lokacin da aka yi amfani da wutar lantarki mai gaba, electrons daga yankin n-type da ramuka daga yankin p-type ana shigar da su cikin yankin aiki. Lokacin da waɗannan masu ɗaukar caji suka sake haɗuwa, suna sakin makamashi ta hanyar photons (haske). Takamaiman abun da ke ciki na Aluminum, Indium, Gallium, da Phosphide a cikin layin aiki yana ƙayyade makamashin bandgap na semiconductor, wanda kai tsaye yake ƙayyade tsawon zango (launi) na hasken da aka fitar. Don hasken rawaya (~590nm), an ƙera takamaiman makamashin bandgap. Ruwan-ruwan epoxy lens yana rufe guntu, yana ba da kariya ta injiniya, kuma yana siffanta tsarin fitar da haske.

13. Technology Trends

Gabaɗayan yanayin a cikin SMD LEDs don nuni da aikace-aikacen baya yana ci gaba zuwa:

• Increased Efficiency: Developing materials and structures that produce more lumens per watt (lm/W), reducing power consumption for the same light output.
• Miniaturization: Further reduction in package size (footprint and height) to enable ever-slimmer electronic devices. The 0.35mm height of this device is part of this trend.
• Improved Color Rendering and Gamut: For display backlighting, there is a move toward LEDs with narrower spectral peaks and specific wavelengths to enable wider color gamuts (e.g., Rec. 2020).
• Higher Reliability and Lifetime: Advancements in packaging materials (epoxy, silicone) and die attach technologies to withstand higher junction temperatures and harsher environmental conditions, extending operational lifetime.
• Integration: Incorporating multiple LED chips (RGB, RGBW) into a single package or integrating driving electronics (IC) with the LED for simplified design ("smart LEDs").