LTST-S110KRKT Side-View SMD LED Datasheet - Red - 20mA - 2.4V - Technical Documentation

1. Product Overview

LTST-S110KRKT, yanal ışık kaynağı gerektiren uygulamalar için tasarlanmış bir yüzey montaj cihazı (SMD) ışık yayan diyottur (LED). Başlıca olarak, alanın kısıtlı olduğu ve ışığın yanal olarak yönlendirilmesi gereken LCD arka ışık modüllerinde kullanılır. Cihaz, kırmızı spektrum aralığında yüksek verimliliği ve parlaklığı ile bilinen ultra parlak AlInGaP (alüminyum indiyum galyum fosfor) yarı iletken çip kullanır. Su beyazı rengindeki paketleme, maksimum ışık çıkışı sağlar ve lens malzemesi renk sapmasına neden olmaz.

A key advantage of this LED is its compliance with the RoHS (Restriction of Hazardous Substances) directive, making it an environmentally friendly "green product." It is supplied on 8mm carrier tape, wound onto 7-inch diameter reels, compatible with standard EIA (Electronic Industries Alliance) packaging and automated pick-and-place assembly equipment. This compatibility ensures efficient, high-volume production. The device is also designed to withstand common soldering processes, including Infrared (IR) and vapor phase reflow, which are standard in modern electronic assembly.

2. Absolute Maximum Ratings

Absolute maximum ratings define the limits that may cause permanent damage to the device. These ratings are specified at an ambient temperature (Ta) of 25°C. The maximum continuous forward current (DC) is 30 mA. For pulse operation, a peak forward current of 80 mA is allowed under specific conditions (duty cycle 1/10, pulse width 0.1 ms). The maximum power dissipation is 75 mW. To ensure reliable operation at higher temperatures, a derating factor of 0.4 mA/°C is applied linearly starting from 50°C. This means that the allowable forward current decreases as the temperature exceeds 50°C.

The device can withstand a reverse voltage of up to 5 V. The operating and storage temperature range is specified as -55°C to +85°C, indicating its suitability for a wide range of environmental conditions. For soldering, the LED can withstand 260°C wave soldering for 5 seconds, 260°C infrared reflow soldering for 5 seconds, and 215°C vapor phase reflow soldering for 3 minutes. Adhering to these limits during assembly is crucial for maintaining device integrity.

3. Electro-Optical Characteristics

Photoelectric characteristics are measured under standard test conditions of Ta=25°C and an operating current (IF) of 20 mA. Luminous intensity (Iv), a measure of perceived brightness, has a typical value of 54.0 millicandelas (mcd) and a minimum value of 18.0 mcd. The viewing angle (2θ1/2), defined as the full angle at which the intensity drops to half of its axial value, is 130 degrees, providing an extremely wide beam pattern highly suitable for backlight applications.

The peak emission wavelength (λP) is 639 nanometers (nm), located in the red region of the visible spectrum. The dominant wavelength (λd), which defines the perceived color, is 631 nm. The spectral line half-width (Δλ) is 20 nm, indicating the spectral purity of the emitted light. The forward voltage (VF) has a typical value of 2.4 V and a maximum of 2.4 V at 20 mA. The reverse current (IR) is a maximum of 10 microamperes (μA) at a reverse voltage (VR) of 5 V. The device capacitance (C) is measured as 40 picofarads (pF) at zero bias and a frequency of 1 MHz.

4. Binning System

The luminous intensity of LEDs is divided into different bins to ensure brightness consistency in production applications. Binning is based on the minimum and maximum luminous intensity values measured at 20 mA. The bin codes and their corresponding ranges are as follows: M bin (18.0-28.0 mcd), N bin (28.0-45.0 mcd), P bin (45.0-71.0 mcd), Q bin (71.0-112.0 mcd), and R bin (112.0-180.0 mcd). A tolerance of +/- 15% is applied to each intensity bin. This system allows designers to select LEDs with a guaranteed brightness range for their specific application, ensuring uniform illumination when multiple LEDs are used.

5. Welding and Assembly Guide

5.1 Reflow Soldering Temperature Profile

The datasheet provides recommended infrared (IR) reflow soldering temperature profiles for standard (tin-lead) and lead-free soldering processes. For lead-free processes, which typically use SnAgCu solder paste, the temperature profile must be maintained between the component's assembly line and heat resistance line. Adhering to these temperature-time curves is crucial to prevent thermal damage to the LED package, such as delamination or cracking, while ensuring proper solder joint formation.

5.2 Cleaning

Care must be taken when cleaning LEDs after soldering. Unspecified chemical liquids should not be used as they may damage the plastic package. If cleaning is necessary, it is recommended to immerse the LED in ethanol or isopropyl alcohol at room temperature for no more than one minute. Prolonged exposure or the use of strong solvents may degrade the lens material or epoxy resin packaging material.

5.3 Storage and Operation

For long-term storage, LEDs should be kept in an environment not exceeding 30°C and 70% relative humidity. If removed from the original moisture-proof packaging, LEDs should undergo infrared reflow soldering within one week. For storage outside the original packaging for more than one week, they should be placed in a sealed container with desiccant or in a nitrogen environment. LEDs stored in this manner for over a week must be baked at approximately 60°C for at least 24 hours before assembly to remove absorbed moisture and prevent the "popcorn" effect during reflow soldering.

6. Mechanical and Packaging Information

LED ina toleo la kifurushi cha mkanda uliojikunja kwenye spool inayofaa kwa usanikishaji wa kiotomatiki. Upana wa mkanda ni 8mm, umekunjwa kwenye spool ya kawaida yenye kipenyo cha inchi 7 (178mm). Kila spool ina vipande 3000. Kwa idadi chini ya spool nzima, kiwango cha chini cha vipande vilivyobaki kwenye kifurushi ni 500. Ufungaji unafuata mwongozo ANSI/EIA 481-1-A-1994. Mfuko tupu kwenye mkanda umefungwa na mkanda wa kifuniko. Idadi kubwa ya ruhusa ya mifuko tupu mfululizo ni miwili, ili kuhakikisha usambazaji thabiti katika vifaa vya kiotomatiki. Mchoro wa kina wa vipimo wa mkanda, spool, na mpangilio wa pedi unaopendekezwa kwenye PCB umetolewa kusaidia muundo wa PCB na usanidi wa mchakato wa usanikishaji.

7. Application Notes and Design Considerations

7.1 Driving Circuit Design

LED is a current-driven device. To ensure uniform brightness when driving multiple LEDs in parallel, it is strongly recommended to connect a current-limiting resistor in series with each LED (Circuit Model A). It is not recommended to directly drive LEDs in parallel without using individual resistors (Circuit Model B). Slight differences in the forward voltage (VF) characteristics between individual LEDs can lead to significant current imbalance, resulting in noticeable brightness variations and potentially subjecting some devices to excessive stress.

7.2 Electrostatic Discharge (ESD) Protection

LED yana da hankali ga zubar da wutar lantarki (ESD) da kuma karuwar wutar lantarki, wanda zai iya haifar da lalacewa nan take ko kuma a nan gaba. Don hana lalacewar ESD, dole ne a bi tsarin aiki daidai: Ma'aikata yakamata su yi amfani da bandeji na wuyan hannu masu kai wutar lantarki ko safofin hannu masu hana wutar lantarki. Duk kayan aiki, teburin aiki da kuma shiryayyun ajiya dole ne a kafa su daidai. Ana iya amfani da injin iska mai ions don daidaita cajin wutar lantarki da ke iya taruwa akan ruwan tabarau na filastik yayin aiki saboda gogayya. LED da aka lalata ta hanyar ESD na iya nuna halayen da ba na al'ada ba, kamar raguwar fitar da haske, karuwar zubar da wutar lantarki, ko kuma gaza gaba daya.

7.3 Application Scope and Reliability

Wadannan LED sun dace da na'urorin lantarki na yau da kullun, ciki har da na'urorin ofis, na'urorin sadarwa da kuma na'urorin gida. Don aikace-aikacen da ke bukatar matukar amincewa, inda gazawar za ta iya yin barazana ga rayuwa ko lafiya (kamar jiragen sama, sufuri, tsarin kiwon lafiya ko kayan aikin tsaro), ana bukatar tuntuba da kuma takaddun shaida na karin kafin amfani.

8. Performance Curves and Typical Characteristics

The datasheet references typical performance curves, which graphically represent the relationships between various parameters. These curves are typically plotted with forward current or ambient temperature on the horizontal axis, including the relationship between forward voltage (VF) and forward current (IF), luminous intensity (Iv) and forward current (IF), and luminous intensity versus ambient temperature. Analyzing these curves helps designers understand the device's behavior under different operating conditions. For example, luminous intensity generally decreases as ambient temperature increases, which must be considered in thermal management. Forward voltage has a negative temperature coefficient, meaning it slightly decreases as the junction temperature rises.

9. Technical Comparison and Advantages

The use of AlInGaP technology to manufacture red chips offers significant advantages over older technologies such as GaAsP. AlInGaP LEDs typically provide higher luminous efficiency, better temperature stability, and longer service life. The side-view package geometry is a key differentiator, enabling light emission parallel to the mounting plane. This is crucial for edge-lit backlight systems commonly found in LCD displays for consumer electronics, automotive dashboards, and industrial panels, as these systems have extremely limited vertical space. A wide viewing angle of 130 degrees ensures good light diffusion and uniformity across the entire backlight area.

10. Frequently Asked Questions (FAQ)

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength (λP) is the wavelength at which the optical output power is maximum. Dominant wavelength (λd) is derived from the CIE chromaticity diagram and represents the single wavelength that most closely matches the perceived color of the light. For monochromatic LEDs like this red LED, the two are typically close but not identical.

Q: Can I operate this LED continuously at its maximum DC current of 30mA?
A: Ko da yake yana yiwuwa, ba a ba da shawarar don samun mafi kyawun rayuwa da aminci ba, sai dai idan aikace-aikacen ya buƙata. Yin aiki a yanayin 20mA na al'ada ko ƙananan ƙarfin zai rage matsin lamba na zafi kuma ya tsawaita rayuwa. Koyaushe yi la'akari da raguwar ƙimar lokacin da yanayin yanayi ya wuce 50°C.

Q: Me yasa kowane LED da aka haɗa a layi daya yana buƙatar resistor a jere?
A: Akwai ƙayyadaddun ƙirƙira a cikin ƙarfin lantarki na gaba (VF) na LED. Idan babu resistor daban, LED tare da VF ɗan ƙasa zai ɗauki ƙarin ƙarfi ba daidai ba, yana haifar da rashin daidaiton haske da yuwuwar gazawar wuce gona da iri. Resistor yana aiki azaman mai sarrafa ƙarfin lantarki mai sauƙi kuma mai inganci ga kowane LED.

Q: Is baking always required before soldering?
A: Baking is only required if the LED has been removed from its original moisture barrier packaging and stored in an uncontrolled environment for more than one week. This process removes absorbed moisture to prevent damage from vapor pressure during high-temperature reflow soldering.

11. Design and Application Case Studies

Consider designing backlighting for a small monochrome LCD display in a handheld medical device. The display requires uniform red backlighting for nighttime readability. The LTST-S110KRKT is selected due to its side-emitting characteristics, suitable for installation within slim bezels. Four LEDs are placed along one side of the light guide plate. Based on the required brightness and light guide efficiency, the designer chooses the N-bin (28-45 mcd) LEDs to ensure sufficient intensity. A constant current driver is used, with each LED having its own 100-ohm series resistor, calculated for a 20mA drive current from a 5V supply. The PCB layout follows recommended pad dimensions to ensure proper soldering and alignment. During assembly, ESD precautions are strictly followed, and the recommended lead-free reflow temperature profile is used. The final product achieves uniform illumination, low power consumption, and high reliability.

12. Working Principle

An LED is a semiconductor p-n junction diode. When a forward voltage is applied, electrons from the n-type region and holes from the p-type region are injected into the junction area. When these carriers recombine, energy is released in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the energy bandgap of the semiconductor material. The bandgap of the AlInGaP material system used in this LED corresponds to red light. The side-emitting package contains a molded plastic lens that shapes the emitted light, directing it laterally from the top surface of the component.

13. Technology Trends

Gabaɗayan yanayin fasahar LED yana zuwa ga mafi inganci (lumens da yawa kowace watt), mafi kyawun bayyana launi, da mafi ingantaccen aminci. Don aikace-aikacen nuna alama da hasken baya, ƙananan ƙirar ci gaba, ƙananan girman kunshe ya zama ma'auni. Hakanan, an mai da hankali kan haɓaka dacewa tare da ci-gaban aikin walda mai ƙarancin zafin jiki, don dacewa da allunan thermal masu hankali. Bugu da ƙari, buƙatar samun mafi haske a cikin ƙaramin kunshe yana haifar da ci gaba a cikin ƙirar guntu da sarrafa zafi a cikin kunshe. Siffar LED mai haske na gefe yana da mahimmanci har yanzu don ƙirar nuni mai sirara a cikin na'urorin hannu da na'urorin lantarki masu sawa.