SMD LED LTST-C990KSKT-BL Datasheet - Dimensions 3.2x2.8x1.9mm - Voltage 1.8-2.4V - Power 62.5mW - Yellow - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTST-C990KSKT-BL, a surface-mount device (SMD) LED lamp. Designed for automated printed circuit board (PCB) assembly, this component is ideal for space-constrained applications across a wide range of consumer and industrial electronics.

1.1 Core Advantages and Target Market

The primary advantages of this LED include its miniature footprint, high brightness output from an AlInGaP semiconductor chip, and full compatibility with automated pick-and-place machinery and infrared (IR) reflow soldering processes. It is engineered to meet RoHS compliance standards. Its target applications are diverse, encompassing telecommunications equipment (e.g., cordless and cellular phones), office automation devices like notebook computers, network systems, home appliances, and indoor signage or symbol illumination. Specific uses include keypad or keyboard backlighting, status indicators, micro-displays, and general signal luminaires.

2. Technical Parameters: In-Depth Objective Interpretation

The following sections detail the critical electrical, optical, and thermal parameters that define the performance envelope of the LED.

2.1 Absolute Maximum Ratings

These ratings specify the limits beyond which permanent damage to the device may occur. They are not intended for normal operation. At an ambient temperature (Ta) of 25°C: The maximum continuous DC forward current (IF) is 25 mA. The device can handle a higher peak forward current of 60 mA, but only under pulsed conditions with a 1/10 duty cycle and a pulse width of 0.1 ms. The maximum permissible reverse voltage (VR) is 5 V. The total power dissipation should not exceed 62.5 mW. The operating temperature range is from -30°C to +85°C, while the storage temperature range extends from -40°C to +85°C. The component can withstand infrared reflow soldering with a peak temperature of 260°C for a duration of 10 seconds.

2.2 Electro-Optical Characteristics

These characteristics are measured under standard test conditions (Ta=25°C, IF=20 mA) and represent typical performance. The luminous intensity (Iv), a measure of perceived brightness, ranges from a minimum of 450.0 mcd to a maximum of 1120.0 mcd. The viewing angle, defined as 2θ1/2 where the intensity is half the axial value, is 75 degrees, indicating a relatively wide beam pattern. The peak emission wavelength (λP) is typically 591.0 nm. The dominant wavelength (λd), which defines the perceived color point on the CIE chromaticity diagram, is specified between 584.5 nm and 594.5 nm, placing it firmly in the yellow region of the spectrum. The spectral line half-width (Δλ) is approximately 15 nm. The forward voltage (VF) at 20 mA ranges from 1.8 V to 2.4 V. The reverse current (IR) at 5 V is 10 µA maximum.

2.3 Thermal Considerations

While not explicitly detailed in curves within the provided extract, the maximum power dissipation of 62.5 mW and the specified operating temperature range are key thermal parameters. Designers must ensure that the PCB layout and application environment allow for adequate heat dissipation to keep the junction temperature within safe limits, as exceeding the maximum ratings will degrade performance and lifespan.

3. Bin Ranking System Explanation

To ensure color and brightness consistency in production, LEDs are sorted into bins based on measured parameters. This system allows designers to select components that meet specific application requirements.

3.1 Forward Voltage (VF) Binning

For the yellow variant, forward voltage is sorted into two bins at a test current of 20 mA: Bin F2 (1.80 V to 2.10 V) and Bin F3 (2.10 V to 2.40 V). The tolerance for each bin is ±0.1 V. Selecting LEDs from the same VF bin helps maintain uniform current distribution when multiple devices are connected in parallel.

3.2 Luminous Intensity (Iv) Binning

Luminous intensity is categorized into two bins: Bin U (450.0 mcd to 710.0 mcd) and Bin V (710.0 mcd to 1120.0 mcd). The tolerance is ±15% of the bin range. This allows for selection based on required brightness levels, with Bin V offering higher output.

3.3 Hue (Dominant Wavelength) Binning

The dominant wavelength, determining the precise shade of yellow, is divided into four bins: Bin H (584.5 nm to 587.0 nm), Bin J (587.0 nm to 589.5 nm), Bin K (589.5 nm to 592.0 nm), and Bin L (592.0 nm to 594.5 nm). The tolerance for each bin is ±1 nm. This precise binning is crucial for applications requiring strict color matching, such as multi-LED displays or status indicators where color consistency is paramount.

4. Performance Curve Analysis

While the specific graphical curves are referenced but not displayed in the text, typical plots for such a device would include the following, providing deeper insight into performance under varying conditions.

4.1 Forward Current vs. Forward Voltage (I-V Curve)

This curve shows the non-linear relationship between the current flowing through the LED and the voltage drop across it. It is essential for designing the current-limiting circuitry (e.g., series resistor or constant current driver) to ensure stable operation at the desired brightness level without exceeding the maximum current rating.

4.2 Luminous Intensity vs. Forward Current

This plot illustrates how light output increases with forward current. It is typically linear over a range but will saturate at higher currents. Operating near the maximum DC current may offer higher brightness but can reduce efficiency and accelerate lumen depreciation over time.

4.3 Luminous Intensity vs. Ambient Temperature

This characteristic curve demonstrates the negative impact of rising junction temperature on light output. As temperature increases, luminous intensity generally decreases. Understanding this derating is critical for applications operating in elevated temperature environments to ensure sufficient brightness is maintained.

4.4 Spectral Distribution

A spectral plot would show the relative radiant power emitted as a function of wavelength, centered around the 591 nm peak with a ~15 nm half-width. This confirms the monochromatic yellow emission of the AlInGaP chip.

5. Mechanical and Package Information

5.1 Package Dimensions

The LED is housed in a standard EIA-compliant SMD package. Key dimensions include a length of 3.2 mm, a width of 2.8 mm, and a height of 1.9 mm. All dimensional tolerances are ±0.1 mm unless otherwise specified. The device features a water-clear dome lens which helps in achieving the 75-degree viewing angle.

5.2 Recommended PCB Attachment Pad Layout

A suggested land pattern (footprint) for PCB design is provided to ensure reliable soldering and proper mechanical alignment. Adhering to this recommended pad geometry is crucial for achieving good solder fillets and preventing tombstoning during reflow.

5.3 Polarity Identification

The cathode (negative) terminal is typically marked on the device body, often by a notch, a green dot, or a cut corner on the lens or package. Correct polarity orientation must be observed during assembly to ensure proper function.

6. Soldering and Assembly Guidelines

6.1 Infrared Reflow Soldering Parameters

For lead-free (Pb-free) solder processes, a specific reflow profile is recommended. The peak body temperature should not exceed 260°C, and the time above 260°C should be limited to a maximum of 10 seconds. The device should only be subjected to a maximum of two reflow cycles under these conditions. A pre-heat stage between 150°C and 200°C for up to 120 seconds is advised to minimize thermal shock. These parameters align with JEDEC standards to ensure reliable solder joints without damaging the LED package.

6.2 Hand Soldering Instructions

If hand soldering is necessary, the soldering iron tip temperature should be kept at or below 300°C. The contact time for each solder joint should be limited to a maximum of 3 seconds, and this should be performed only once per joint to prevent excessive heat transfer to the semiconductor die.

6.3 Storage Conditions

Unopened moisture-sensitive bags (MSL 3) should be stored at ≤ 30°C and ≤ 90% relative humidity (RH) and used within one year. Once the original sealed packaging is opened, the LEDs should be stored in an environment not exceeding 30°C and 60% RH. It is strongly recommended to complete the IR reflow process within one week after opening. For longer storage outside the original bag, components should be kept in a sealed container with desiccant or in a nitrogen-purged desiccator. If stored for more than one week outside the original packaging, a bake-out at approximately 60°C for at least 20 hours is required before soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

6.4 Cleaning Procedures

If cleaning after soldering is required, only specified alcohol-based solvents such as isopropyl alcohol (IPA) or ethyl alcohol should be used. The LED should be immersed at normal room temperature for less than one minute. Unspecified chemical cleaners may damage the epoxy lens or package.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied in embossed carrier tape on 7-inch (178 mm) diameter reels, in accordance with ANSI/EIA-481 standards. Each reel contains 3000 pieces. The tape pocket dimensions are designed to securely hold the 3.2x2.8mm component. A top cover tape seals the pockets. The maximum allowable number of consecutive missing components in the tape is two. For quantities less than a full reel, a minimum packing quantity of 500 pieces is available for remainder orders.

8. Application Recommendations

8.1 Typical Application Circuits

The LED must be driven with a constant current or via a current-limiting resistor connected in series with a voltage source. The series resistor value (R_s) can be calculated using Ohm's Law: R_s = (V_supply - V_F) / I_F, where V_F is the forward voltage of the LED at the desired current I_F (e.g., 20 mA). Using the maximum V_F of 2.4 V ensures the resistor is sized conservatively to limit current under all bin conditions.

8.2 Design Considerations and Precautions

ESD Sensitivity: The LED is sensitive to electrostatic discharge (ESD). Proper ESD controls must be in place during handling and assembly, including the use of grounded wrist straps, anti-static mats, and ESD-safe equipment.
Current Control: Never connect the LED directly to a voltage source without current limiting, as this will cause excessive current flow, immediate overheating, and catastrophic failure.
Heat Management: Ensure the PCB layout provides adequate thermal relief, especially when operating at or near the maximum DC current. Avoid placing the LED near other significant heat sources.
Application Scope: This component is designed for general-purpose electronic equipment. It is not rated for applications where failure could pose a direct risk to life or safety, such as in aviation, medical life-support, or critical transportation control systems without prior consultation and qualification.

9. Technical Comparison and Differentiation

The LTST-C990KSKT-BL differentiates itself through its use of an AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material for the light-emitting chip. Compared to older technologies like standard GaP (Gallium Phosphide), AlInGaP offers significantly higher luminous efficiency, resulting in greater brightness (up to 1120 mcd) for a given current. The water-clear lens, as opposed to a diffused or colored lens, maximizes light extraction and contributes to the well-defined 75-degree viewing angle. Its full compatibility with high-volume, automated SMT assembly processes, including aggressive IR reflow profiles, makes it a cost-effective and reliable choice for modern electronics manufacturing.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength (λP) is the single wavelength at which the emitted optical power is maximum (591 nm typical). Dominant wavelength (λd) is derived from the CIE color coordinates and represents the single wavelength of a pure monochromatic light that would match the perceived color of the LED (584.5-594.5 nm). λd is more relevant for color specification.

Q: Can I drive this LED with a 3.3V supply?
A: Yes, but a series resistor is mandatory. Using the maximum V_F of 2.4V and a target I_F of 20mA, the resistor value would be R = (3.3V - 2.4V) / 0.02A = 45 Ohms. A standard 47 Ohm resistor would be a suitable choice, resulting in a slightly lower current.

Q: Why is binning important?
A: Binning ensures consistency in production. For example, using LEDs all from Bin V for luminous intensity and Bin K for wavelength guarantees that all indicators in a panel will have nearly identical brightness and the same shade of yellow, which is critical for product quality and aesthetics.

Q: What does \"MSL 3\" mean for storage?
A: Moisture Sensitivity Level 3 indicates that the packaged device can be exposed to factory floor conditions (≤ 30°C/60% RH) for up to 168 hours (7 days) before it requires baking to remove moisture that could cause internal damage during the high-temperature reflow soldering process.

11. Practical Use Case Example

Scenario: Designing a status indicator panel for a network router.
The panel requires four yellow LEDs to indicate \"Power,\" \"Internet,\" \"Wi-Fi,\" and \"Ethernet\" status. To ensure uniform appearance, the designer specifies LEDs from Bin V (for high, consistent brightness) and Bin J (for a specific yellow hue). The circuit is powered from the router's 5V rail. A series resistor is calculated using the maximum V_F to be safe: R = (5V - 2.4V) / 0.02A = 130 Ohms. A 130 Ohm, 1/8W resistor is placed in series with each LED. The PCB layout uses the recommended pad footprint and includes small thermal relief spokes on the cathode pads. The assembly house follows the provided IR reflow profile. The final product exhibits four bright, perfectly matched yellow indicators that are clearly visible from a wide angle.

12. Operating Principle Introduction

Light emission in this LED is based on electroluminescence in a semiconductor chip composed of AlInGaP. When a forward voltage exceeding the chip's bandgap voltage (around 2V) is applied, electrons and holes are injected into the active region from the n-type and p-type semiconductor layers, respectively. These charge carriers recombine, releasing energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly defines the wavelength (color) of the emitted light—in this case, yellow. The water-clear epoxy lens encapsulates the chip, providing mechanical protection, shaping the light output beam (75-degree viewing angle), and enhancing light extraction from the semiconductor material.

13. Technology Trends and Context

The use of AlInGaP material for yellow, orange, and red LEDs represents an established high-performance technology, offering superior efficiency and brightness compared to older GaAsP and GaP solutions. Current trends in SMD LEDs focus on increasing efficiency (lumens per watt), achieving higher maximum drive currents and power ratings in smaller packages, improving color rendering and saturation, and enhancing reliability under harsh environmental conditions. Furthermore, integration with intelligent drivers and the development of chip-scale package (CSP) LEDs that eliminate the traditional plastic package are ongoing areas of advancement. The component described here utilizes a proven, reliable technology optimized for cost-effective, high-volume manufacturing in mainstream consumer and industrial applications.