SMD LED LTST-E681VEWT Datasheet - Size 2.8x3.5x1.9mm - Voltage 2.2V - Power 196mW - Red - Technical Documentation

1. Product Overview

LTST-E681VEWT, modern elektronik uygulamalar için güvenilir ve verimli gösterge aydınlatması gereksinimlerine özel olarak tasarlanmış, yüksek parlaklıklı bir yüzey montaj LED'idir. Bu cihaz, canlı kırmızı ışık çıkışı üreten AlInGaP (alüminyum indiyum galyum fosfit) yarı iletken malzemesini kullanır. Kompakt, endüstri standardı paketi, otomatik montaj süreçleriyle uyumludur ve yüksek hacimli üretim için uygundur.

Faida kuu ya LED hii ni pamoja na kufuata maagizo ya RoHS (Vizuizi vya Vitu Hatari), kuhakikisha usalama wa mazingira. Inafungwa kwenye mkanda wa kubeba wa 8mm, uliozungukwa kwenye reeli yenye kipenyo cha inchi 7, ambayo ni usanidi wa kawaida wa vifaa vya kushikamanisha vya otomatiki. Kifaa hiki pia kimeundwa kufanana na mchakato wa kuunganishia kwa kuyeyusha kwa mionzi ya infrared, ambayo ni njia kuu ya kukusanya bodi za teknolojia ya kushikamana na uso. Soko lake kuu lengwa linajumuisha elektroniki za watumiaji, paneli za udhibiti wa viwanda, taa za ndani za magari, na matumizi ya jumla ya viashiria vya mwanga ambapo nafasi ni ndogo na uaminifu ni muhimu sana.

2. In-depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation of the LED outside these values is not recommended.

• Power Dissipation (Pd):196 mW. This is the maximum power that the LED package can dissipate as heat when the ambient temperature (Ta) is 25°C. Exceeding this limit risks overheating and damaging the semiconductor junction, leading to reduced lifespan or catastrophic failure.
• Peak Forward Current (I_FP):100 mA. This is the maximum permissible pulse forward current, specified under conditions of a duty cycle of 1/10 and a pulse width of 1ms. It is significantly higher than the DC rating, allowing for brief, high-intensity flashing.
• DC Forward Current (I_F):70 mA. This is the maximum continuous forward current that can be applied to the LED under normal operating conditions.
• Operating Temperature Range:-40°C to +85°C. The LED is designed to operate normally within this ambient temperature range.
• Storage temperature range:-40°C to +100°C. The device can be stored within this wider temperature range without degradation when not in operation.

2.2 Electrical and Optical Characteristics

These parameters are measured under standard test conditions of Ta=25°C and I_F=50mA unless otherwise specified. They define the typical performance of the device.

• Luminous Intensity (I_V):900 to 2800 mcd (millicandela). This measures the perceived power of light emitted in a specific direction. The wide range indicates the use of a binning system (see Section 3 for details). Measurements use a filtered sensor to approximate the photopic response of the human eye (CIE curve).
• Viewing angle (2θ_1/2):120 degrees. This is the full angle at which the luminous intensity drops to half of its axial (0°) measured value. A 120° viewing angle implies a broad, diffuse light pattern, suitable for applications requiring wide visibility.
• Peak Emission Wavelength (λ_P):632 nm (typical). This is the wavelength at which the spectral power distribution of the emitted light reaches its maximum. It falls within the red region of the visible spectrum.
• Dominant Wavelength (λ_d):624 nm (typical). Derived from the CIE chromaticity diagram, this is the single wavelength that best represents the LED color perceived by the human eye. It is a key parameter for color specification.
• Spectral Line Half-Width (Δλ):20 nm (typical value). This is the width of the spectral emission at half its maximum power. The value of 20nm is characteristic of AlInGaP red LEDs, indicating relatively pure color.
• Forward voltage (V_F):2.2 V (typical value), with a tolerance of ±0.1V. This is the voltage drop across the LED when driven at the specified 50mA current. It is crucial for designing current-limiting circuits.
• Reverse current (I_R):In V_R=5V, maximum 10 μA. This parameter is for quality assurance testing only. This LEDis not designed for reverse bias operation.Applying reverse voltage in a circuit may damage it.

3. Grading System Description

To ensure consistency in mass production, LEDs are binned according to their performance. The LTST-E681VEWT uses a binning system based on luminous intensity at 50mA.

The binning codes (V2, W1, W2, X1, X2) represent increasing ranges of minimum and maximum luminous intensity. For example, bin code X2 includes LEDs with intensities between 2240 mcd and 2800 mcd. A tolerance of ±11% is applied within each bin. This system allows designers to select the appropriate brightness level for their application, balancing cost and performance. This datasheet does not indicate separate binning for dominant wavelength or forward voltage for this specific model, suggesting tight control of these parameters during manufacturing.

4. Performance Curve Analysis

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

• I-V (Current-Voltage) Curve:It shows the exponential relationship between forward current and forward voltage. The curve has a distinct "knee" voltage at approximately 1.8-2.0V, beyond which the current increases rapidly with a small increase in voltage, highlighting why constant current drive is crucial.
• Luminous Intensity vs. Forward Current:It shows that the light output is roughly proportional to the forward current, but may exhibit saturation or a drop in efficiency at extremely high currents.
• Luminous Intensity vs. Ambient Temperature:It shows that the light output decreases as the junction temperature increases. This is a key consideration for applications operating in high-temperature environments.
• Spectral Distribution:A graph showing the relationship between relative power and wavelength, indicating a peak at approximately 632nm and a full width at half maximum of about 20nm.
• Viewing Angle Distribution Diagram:A polar plot showing the angular distribution of light intensity, confirming a 120° viewing angle due to the diffuser lens and exhibiting a Lambertian or near-Lambertian distribution.

5. Mechanical and Packaging Information

5.1 Device Dimensions

This LED complies with the EIA standard SMD package. Key dimensions (unit: mm) are as follows:

• Total length: 3.2 mm
• Total width: 2.8 mm
• Total height: 1.9 mm
• Lens width: 2.2 mm
• Lens length: 3.5 mm
• Pin width: 0.7 mm
• Pin length: 0.8 mm

Unless otherwise specified, the tolerance is ±0.2mm. The original specification sheet provides a detailed dimensional drawing.

5.2 Polarity Identification and Pad Design

The anode (positive) connection is identified. To ensure soldering reliability, a recommended printed circuit board land pattern is provided, optimized for infrared and vapor phase reflow soldering processes. Proper pad design is critical to prevent tombstoning (component lifting on one end) and to ensure reliable solder joints with appropriate solder paste volume.

6. Soldering and Assembly Guide

6.1 Reflow soldering parameters

The device is compatible with lead-free infrared reflow soldering. The recommended temperature profile should comply with JEDEC standard J-STD-020B. Key parameters include:

• Preheat:150-200°C, maximum 120 seconds, to gradually heat the circuit board and components, activate the flux, and prevent thermal shock.
• Peak Temperature:Maximum 260°C. Time above liquidus (typically 217°C for lead-free solder) should be controlled.
• Total Soldering Time:A cikin zafin jiki mafi girma har zuwa dakika 10. Yin amfani da wutar lantarki don haɗa abubuwa ya kamata ya iyakance ga zagaye biyu kawai.

Ya kamata a jaddada cewa mafi kyawun zane-zane na zafin jiki ya dogara da ƙayyadaddun ƙirar PCB, kayan aiki, man gini, da kuma tanda, kuma ya kamata a yi bincike na musamman ga kowane aikace-aikace.

6.2 Manual soldering

If manual soldering is necessary, extreme caution must be exercised:

• Soldering iron temperature:Maximum 300°C.
• Welding time:Maximum 3 seconds per pin, and only one welding cycle is allowed to prevent the plastic package and internal bonding wires from being subjected to excessive thermal stress.

6.3 Storage Conditions

LED is a moisture-sensitive device.

• Sealed packaging:Store at ≤30°C and ≤70% relative humidity. Shelf life is one year when stored in the original moisture barrier bag with desiccant.
• Opened Package:Components must be used within 168 hours (7 days) after exposure to ambient air (≤30°C / ≤60% RH). If this time is exceeded, LEDs need to be baked prior to soldering, at approximately 60°C for at least 48 hours, to remove absorbed moisture and prevent "popcorn" effect (package cracking due to vapor pressure during reflow). For long-term storage of opened packages, use sealed containers with desiccant or nitrogen-filled dryers.

6.4 Cleaning

If post-soldering cleaning is required, only specified alcohol-based solvents such as ethanol or isopropanol should be used, cleaning at room temperature for no more than one minute. Unspecified chemicals may damage the plastic lens or encapsulation.

7. Packaging and Ordering Information

• Carrier Tape Specifications:LEDs are supplied in 8mm wide embossed carrier tape.
• Reel specification:Carrier tape is wound on standard 7-inch (178mm) diameter reels.
• Quantity per roll:2000 pieces.
• Minimum order quantity:Sisa jumlah adalah 500 lembar.
• Standar:Kemasan sesuai dengan spesifikasi ANSI/EIA-481.
• Model:LTST-E681VEWT. Naming conventions typically include series code, package/style, color/wavelength code, and possible other variants.

8. Application Description and Design Considerations

8.1 Drive Circuit Design

LED is a current-driven device. To ensure stable and uniform brightness, especially when driving multiple LEDs in parallel, for each LEDmustbe connected in series with a current-limiting resistor. The resistor value (R) is calculated using Ohm's Law: R = (V_{Power supply}- V_F) / I_F. Using typical V_F= 2.2V, I desired_F= 20mA, with a supply voltage of 5V: R = (5V - 2.2V) / 0.02A = 140 ohms. A standard 150-ohm resistor is suitable. Driving an LED directly from a voltage source without current limiting will result in excessive current and rapid failure.

8.2 Thermal Management

Although the power dissipation is relatively low (196mW), effective thermal management remains important for maintaining long-term reliability and consistent light output. Ensure the PCB has sufficient copper area connected to the LED's thermal pad (if applicable) or leads to aid heat dissipation. Avoid prolonged operation at absolute maximum current and temperature limits.

8.3 Application Scope

Wannan LED ya dace da na'urorin lantarki na gabaɗaya, kamar na'urorin ofis, na'urorin sadarwa, da na'urorin gida. Ba a ƙirƙira shi ko ba shi takaddun shaida don aikace-aikacen aminci masu mahimmanci inda gazawar za ta iya haifar da barazana ga rayuwa ko lafiya (misali, jiragen sama, tallafin rayuwa na likita, sarrafa zirga-zirga). Don irin waɗannan aikace-aikace, dole ne a sayi kayan aiki tare da takaddun shaida na aminci da suka dace.

9. Technical Comparison and Differentiation

The key differentiating advantages of the LTST-E681VEWT in its category include:

• Material Technology:Using AlInGaP, compared to older technologies like GaAsP, it typically offers higher efficiency and better temperature stability for red and amber light.
• Brightness:Maximum intensity up to 2800mcd, providing high brightness within standard package dimensions.
• Perspective:The 120° wide viewing angle with a diffused lens provides excellent off-axis visibility, which is superior to narrow-beam LEDs for status indicators.
• Process Compatibility:Fully compatible with automated SMT assembly and standard lead-free reflow temperature profiles, reducing manufacturing complexity and cost.

10. FAQ (FAQ)

Q: If my power supply voltage is exactly 2.2V, can I drive this LED without a series resistor?
A: Ee, ba. Voltage gaba na daidai (±0.1V) kuma yana canzawa da zafin jiki. Ƙaramin ƙarin wutar lantarki zai haifar da haɓakar kwararar wutar lantarki ba tare da sarrafawa ba, wanda zai iya lalata LED. Dole ne a yi amfani da tsarin iyakance kwararar wutar lantarki.

Q: Menene bambanci tsakanin madaidaicin tsawon zango da babban tsawon zango?
A: Madaidaicin tsawon zango shine wurin da ake fitar da mafi yawan makamashin haske a zahiri. Babban tsawon zango an lissafta shi bisa ga ma'auni na launi, wanda ke wakiltar launin da idon mutum ya gane. Ga LED mai launi ɗaya kamar wannan LED ja, yawanci suna kusa, amma babban tsawon zango shine ma'auni mai mahimmanci na daidaitawar launi.

Q: Kwat ɗin na yana yin tsaftacewa bayan gyarawa. Shin wannan LED ya dace?
A: The datasheet specifies cleaning only with alcohol-based solvents (isopropyl alcohol or ethanol) for no more than one minute. Many water-based or strong flux cleaners may damage the package. Please verify compatibility with your specific cleaning process.

Q: Why is there a 168-hour floor life limit after opening the bag?
A: The plastic package absorbs moisture from the air. At the high temperatures of reflow soldering, this moisture can rapidly turn to steam, causing internal pressure that may crack the package or cause internal layer delamination ("popcorn" effect). The 168-hour limit and baking procedures are in place to manage this risk.

11. Practical Application Examples

Scenario:Design a power status indicator for a 12V DC router.
Design Steps:
1. Select Drive Current:To extend lifespan and reduce heat, choose a conservative I_F= 15mA.
2. Calculate resistance:Use typical V_F= 2.2V. R = (12V - 2.2V) / 0.015A = 653 ohms. Use the nearest standard value, 680 ohms.
3. Calculate resistor power: P_R= I_F²* R = (0.015)²* 680 = 0.153W. Standard 1/4W (0.25W) resistor is sufficient.
4. PCB layout:Place the LED and its 680Ω resistor close together. Follow the recommended pad layout in the datasheet to ensure soldering reliability.
5. Assembly:Yi amfani da tsarin zafin jujjuyawar da ya dace da ma'aunin JEDEC maras gubar. Idan an haɗa allon kewaye bayan buɗe jakar LED fiye da kwanaki 7, to, gasa LED da farko.

12. Working Principle

Hasken haske a cikin LTST-E681VEWT ya dogara ne akan hasken lantarki a cikin mahaɗar p-n semiconductor da aka yi da kayan AlInGaP. Lokacin da aka yi amfani da ƙarfin lantarki mai kyau wanda ya wuce ƙarfin ginin mahaɗar, electrons daga yankin n-type da ramuka daga yankin p-type ana shigar da su cikin yanki mai aiki. Lokacin da waɗannan masu ɗaukar kaya suka haɗu, suna sakin makamashi a cikin nau'in photon (haske). Takamaiman abun da ke cikin gawa na AlInGaP yana ƙayyade ƙarfin tazarar band, wanda kai tsaye yana ayyana tsawon zangon hasken da ake fitarwa (launi) – a cikin wannan misalin, ja, mai tsawon zango kusan 624-632 nm. Ruwan tabarau na epoxy mai watsawa da ke sama da guntu yana aiki don fitar da haske daga cikin semiconductor, kuma ya siffanta rarraba kusurwarsa zuwa tsarin mai faɗin digiri 120.

13. Technical Trends

Gösterge LED'lerinin optoelektronik endüstrisi sürekli gelişmektedir. LTST-E681VEWT gibi cihazlarla ilişkili genel eğilimler şunları içerir:

• Verimlilik Artışı:Continuous improvements in materials science aim to achieve higher lumens per watt, enabling brighter output at the same current or lower power consumption and less heat at the same brightness.
• Miniaturization:While standard packages like these remain prevalent, there is constant pressure to reduce the package footprint and height for increasingly slim electronic devices.
• Reliability Enhancement:Improvements in packaging materials, die attach technology, and bonding wires aim to extend operational lifespan and enhance resistance to thermal and mechanical stress.
• Color Consistency:More stringent binning tolerances and advanced manufacturing controls are reducing color and brightness variations between batches, which is crucial for applications using multiple LEDs.
• Integration:There is a trend towards integrating driver circuits, protection functions (such as ESD diodes), or multiple LED chips into a single package, although in many applications, discrete LEDs remain fundamental due to their simplicity and cost advantages.