SMD LED LTST-C950RKRKT-5A Datasheet - Red AlInGaP - 5mA - 180-710mcd - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a high-brightness, surface-mount LED designed for automated assembly processes. The device utilizes an advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material to produce red light, offering superior luminous efficiency and color purity compared to traditional LED technologies. Encapsulated in a water-clear dome lens, the LED is packaged in a standard EIA-compliant footprint, making it compatible with a vast array of automated pick-and-place and infrared reflow soldering equipment commonly used in modern electronics manufacturing.

The core advantages of this LED include its compact form factor, suitability for space-constrained applications, and compliance with RoHS (Restriction of Hazardous Substances) directives. It is engineered for reliability in demanding environments, with a specified operating temperature range. The primary target markets and applications span across telecommunications infrastructure, office automation equipment, home appliances, industrial control panels, and consumer electronics. Specific use cases include backlighting for keypads and keyboards, status and power indicators, integration into micro-displays, and signal or symbolic illumination in various devices.

2. Technical Parameters Deep Objective Interpretation

2.1 Absolute Maximum Ratings

The absolute maximum ratings define the stress limits beyond which permanent damage to the device may occur. These values are specified at an ambient temperature (Ta) of 25°C. The maximum continuous forward current (DC) is 30 mA. For pulsed operation, a peak forward current of 80 mA is permissible under specific conditions: a 1/10 duty cycle and a pulse width of 0.1 ms. The maximum power dissipation is 75 mW. The device can operate within an ambient temperature range of -30°C to +85°C and can be stored between -40°C and +85°C. A critical rating for assembly is the infrared soldering condition, which is rated for a peak temperature of 260°C for a maximum duration of 10 seconds, which is standard for Pb-free (lead-free) reflow processes.

2.2 Electro-Optical Characteristics

The electro-optical characteristics are measured under standard test conditions at Ta=25°C and a forward current (IF) of 5 mA, unless otherwise noted. The luminous intensity (Iv), a key measure of brightness, has a wide typical range from 180.0 mcd (millicandela) to 710.0 mcd, which is further categorized into specific bins. The viewing angle, defined as 2θ1/2 where the intensity is half the axial value, is 25 degrees, indicating a relatively focused beam pattern. The peak emission wavelength (λP) is typically 639 nm, falling within the red spectrum. The dominant wavelength (λd), which defines the perceived color, is typically 631 nm. The spectral line half-width (Δλ) is 20.0 nm, describing the spectral purity of the emitted light. The forward voltage (VF) ranges from a minimum of 1.6 V to a maximum of 2.2 V at 5 mA. The reverse current (IR) is specified at a maximum of 10 µA when a reverse voltage (VR) of 5 V is applied.

3. Binning System Explanation

3.1 Luminous Intensity Binning

To ensure consistency in brightness for production applications, the LEDs are sorted into bins based on their measured luminous intensity at 5 mA. The bin code list is as follows: Bin Code \"S\" covers intensities from 180.0 mcd to 280.0 mcd. Bin Code \"T\" covers intensities from 280.0 mcd to 450.0 mcd. Bin Code \"U\" covers intensities from 450.0 mcd to 710.0 mcd. A tolerance of +/- 15% is applied to the limits of each luminous intensity bin. This binning allows designers to select LEDs with guaranteed minimum brightness levels for their specific application requirements, ensuring visual uniformity in products using multiple LEDs.

4. Performance Curve Analysis

While specific graphical data is referenced in the document (e.g., Figure 1 for spectral measurement, Figure 5 for viewing angle), the typical performance curves for this type of device would generally include several key relationships. The Forward Current vs. Forward Voltage (I-V) curve would show the exponential relationship characteristic of a diode, with the voltage rising sharply after the turn-on threshold. The Luminous Intensity vs. Forward Current curve would typically show a near-linear increase in brightness with current up to a point, after which efficiency may drop due to thermal effects. The Luminous Intensity vs. Ambient Temperature curve is crucial, as LED output generally decreases as junction temperature increases. For a red AlInGaP LED, the intensity degradation with temperature is typically less severe than for some other LED technologies but is still a critical design factor. The Spectral Distribution curve would show a single peak centered around 639 nm with a defined half-width, confirming the color purity.

5. Mechanical and Package Information

5.1 Package Dimensions and Polarity

The LED is housed in a standard surface-mount device (SMD) package. The lens color is water clear, and the light source color is red from the AlInGaP chip. All critical package dimensions are provided in millimeters, with a standard tolerance of ±0.1 mm unless otherwise specified. The datasheet includes a detailed dimensional drawing showing the length, width, height, lead spacing, and other critical mechanical features. Polarity is indicated by the physical design of the package, typically with a cathode mark (such as a notch, dot, or beveled corner) on one end. Correct orientation during placement on the printed circuit board (PCB) is essential for proper operation.

5.2 Recommended PCB Attachment Pad

A recommended land pattern (footprint) for the PCB is provided to ensure reliable soldering and mechanical stability. This pattern specifies the size and shape of the copper pads for the anode and cathode, as well as the recommended solder mask opening. Adhering to this recommended footprint helps achieve proper solder fillet formation, prevents tombstoning (component standing on end), and ensures good thermal and electrical connection.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Parameters

For lead-free (Pb-free) assembly processes, a specific reflow soldering profile is recommended. The profile includes a pre-heat stage in the range of 150°C to 200°C, with a maximum pre-heat time of 120 seconds to gradually heat the board and component and activate the flux. The peak body temperature should not exceed 260°C. The time above the liquidus temperature of the solder (typically around 217°C for SAC alloys) and specifically the time within 5°C of the peak temperature should be controlled; the datasheet specifies a maximum of 10 seconds at peak temperature. The device should not be subjected to more than two reflow cycles under these conditions. It is emphasized that the optimal profile depends on the specific PCB design, solder paste, and oven, and should be characterized accordingly, using JEDEC standards as a guideline.

6.2 Manual Soldering

If manual soldering with an iron is necessary, extreme care must be taken. The soldering iron tip temperature should not exceed 300°C, and the contact time with the LED terminal should be limited to a maximum of 3 seconds per joint. Manual soldering should be performed only once to avoid thermal stress damage to the internal die and wire bonds.

6.3 Storage and Handling

The LEDs are moisture-sensitive devices (MSL 3). When stored in their original sealed moisture-proof bag with desiccant, they should be kept at 30°C or less and 90% relative humidity (RH) or less, and used within one year. Once the original packaging is opened, the storage environment should not exceed 30°C and 60% RH. Components removed from their original packaging should ideally be IR-reflowed within one week. For longer storage outside the original bag, they must be stored in a sealed container with desiccant or in a nitrogen desiccator. If stored unpackaged for more than one week, a bake-out at approximately 60°C for at least 20 hours is required before solder assembly to remove absorbed moisture and prevent \"popcorning\" damage during reflow.

6.4 Cleaning

If cleaning after soldering is required, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute is acceptable. The use of unspecified chemical cleaners can damage the epoxy lens and package material.

6.5 Electrostatic Discharge (ESD) Precautions

The LED is sensitive to electrostatic discharge and surge currents, which can degrade or destroy the semiconductor junction. Proper ESD controls must be implemented during handling and assembly. This includes the use of grounded wrist straps, anti-static gloves, and ensuring all equipment and work surfaces are properly grounded.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied packaged for automated assembly. They are mounted in embossed carrier tape with a width of 12 mm. The tape is wound onto a standard 7-inch (178 mm) diameter reel. Each reel contains 2000 pieces. For quantities less than a full reel, a minimum packing quantity of 500 pieces is available for remainder stock. The tape has a top cover seal to protect the components. The packaging conforms to ANSI/EIA-481 specifications. A maximum of two consecutive missing components (empty pockets) is allowed per reel.

8. Application Suggestions

8.1 Drive Circuit Design

An LED is a current-operated device. To ensure consistent brightness and longevity, it must be driven with a controlled current, not a fixed voltage. The simplest and most recommended drive method is to use a series current-limiting resistor for each LED, as shown in \"Circuit A\" in the datasheet. This configuration, powered by a voltage source (Vcc), ensures that variations in the forward voltage (VF) of individual LEDs do not cause significant differences in current and, therefore, brightness when multiple LEDs are connected in parallel. The resistor value (R) is calculated using Ohm's Law: R = (Vcc - VF) / IF, where IF is the desired forward current (e.g., 5 mA for testing, up to 30 mA max continuous).

8.2 Thermal Management

While the package is small, managing heat is important for maintaining performance and reliability. The luminous intensity decreases as the junction temperature increases. In applications where the LED is driven at or near its maximum current, or in high ambient temperatures, attention should be paid to the PCB layout. Providing adequate copper area around the LED pads can act as a heat sink, helping to dissipate heat from the device. Avoiding placement near other heat-generating components is also advisable.

8.3 Application Limitations

The device is intended for use in ordinary electronic equipment. For applications requiring exceptional reliability where failure could jeopardize life or health (such as in aviation, medical life-support, or safety-critical systems), specific consultation and qualification are necessary, as standard commercial-grade components may not be suitable.

9. Technical Comparison and Differentiation

Compared to older technologies like GaAsP (Gallium Arsenide Phosphide) red LEDs, the AlInGaP chip used in this device offers significantly higher luminous efficiency, resulting in much greater brightness for the same drive current. The water-clear lens, as opposed to a diffused or colored lens, maximizes light output and provides a more vibrant, saturated color point. The EIA-standard package ensures broad compatibility with industry-standard assembly lines and footprint libraries, reducing design and manufacturing complexity. The device's compatibility with infrared reflow soldering and its moisture sensitivity level (MSL 3) are typical for modern SMD components, aligning it with mainstream, high-volume manufacturing processes.

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 wavelength at which the spectral power distribution is maximum (639 nm). Dominant wavelength (λd) is derived from the CIE chromaticity diagram and represents the single wavelength of the monochromatic light that would match the color of the LED (631 nm). Dominant wavelength is more closely related to the perceived color.

Q: Can I drive this LED at 20 mA continuously?
A: Yes. The maximum continuous forward current is 30 mA. Driving it at 20 mA is within specification. Note that luminous intensity typically increases with current, but the exact value at 20 mA would need to be estimated from the typical performance curves or measured, as the datasheet specifies intensity at 5 mA.

Q: Why is a series resistor necessary even if my power supply voltage matches the LED's forward voltage?
A: The forward voltage (VF) has a range (1.6V to 2.2V). If the supply voltage is fixed at, say, 2.0V, an LED with a VF of 1.6V would experience a much higher current than intended, potentially leading to overheating and failure. The series resistor provides a stable, predictable current regardless of the natural variation in VF from one LED to another.

Q: How do I select the correct bin for my application?
A: Choose a bin based on the minimum brightness required for your design under your specific drive conditions. If uniformity is critical (e.g., in an array of status lights), specifying a single, tighter bin (like T or U) and ordering all units from that bin will ensure consistent appearance. For less critical applications, a broader bin or mixed bins may be acceptable for cost savings.

11. Practical Design and Usage Case

Case: Designing a Status Indicator Panel for a Network Router
A designer is creating a panel with four red status LEDs indicating \"Power,\" \"Internet,\" \"Wi-Fi,\" and \"Ethernet\" activity. The LEDs need to be clearly visible in a well-lit office environment. The system power rail is 3.3V. The designer selects this LED for its high brightness and standard package. To achieve a bright indication, they decide to drive each LED at 10 mA. Using the typical VF of 1.9V, they calculate the series resistor: R = (3.3V - 1.9V) / 0.01A = 140 Ohms. A standard 150 Ohm resistor is chosen. To ensure all four LEDs have matched brightness, the designer specifies Bin \"T\" (280-450 mcd) in the bill of materials. The PCB layout includes the recommended land pattern and a small amount of copper pour around the pads for slight thermal relief. The assembly house uses the provided IR reflow profile, and the final product exhibits consistent, bright, and reliable status indicators.

12. Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light when an electric current passes through them. This particular LED uses an AlInGaP (Aluminum Indium Gallium Phosphide) compound semiconductor for its active region. When a forward voltage is applied, electrons from the n-type material and holes from the p-type material are injected into the active region. When these charge carriers recombine, they release energy in the form of photons (light). The specific bandgap energy of the AlInGaP material determines the wavelength (color) of the emitted light, which in this case is in the red portion of the visible spectrum (approximately 631-639 nm). The water-clear epoxy lens encapsulates the chip, protects it from the environment, and shapes the light output beam.

13. Development Trends

The general trend in SMD LED technology continues toward higher efficiency (more lumens per watt), which allows for either increased brightness at the same power or reduced power consumption for the same light output. There is also a drive toward miniaturization, with packages becoming even smaller while maintaining or improving optical performance. Enhanced reliability and longer operational lifetimes are constant goals, achieved through improvements in chip design, packaging materials, and thermal management. Furthermore, tighter binning and better color consistency are increasingly important for applications requiring high visual quality, such as display backlighting and automotive lighting. The integration of control electronics, such as constant current drivers, within the LED package itself is another growing trend, simplifying circuit design for the end user.