Reverse Mount Chip LED LTST-C230KSKT Datasheet - Yellow - 20mA - 2.4V - English Technical Document

1. Product Overview

This document details the specifications for a high-brightness, reverse mount Chip LED utilizing AlInGaP (Aluminum Indium Gallium Phosphide) technology. The device is designed for surface-mount applications and features a water-clear lens that emits yellow light. It is packaged on 8mm tape wound onto 7-inch diameter reels, making it fully compatible with automated pick-and-place assembly systems and standard infrared (IR) reflow soldering processes. The product adheres to RoHS (Restriction of Hazardous Substances) directives, classifying it as a green product.

1.1 Core Features and Target Market

The primary features of this LED include its reverse-mount design, which can be advantageous for specific optical or mechanical layouts, and the use of an ultra-bright AlInGaP chip, known for its high efficiency and stability. The package conforms to EIA (Electronic Industries Alliance) standards, ensuring broad compatibility. Its I.C. (Integrated Circuit) compatible drive characteristics make it suitable for direct interfacing with microcontroller outputs or driver circuits. This LED is targeted at applications in consumer electronics, industrial indicators, automotive interior lighting, and general backlighting where reliable, automated assembly is required.

2. Technical Parameter Deep-Dive

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. They are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): 75 mW. This is the maximum amount of power the LED package can dissipate as heat.
• Peak Forward Current (I_F(PEAK)): 80 mA. This is permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to prevent overheating.
• DC Forward Current (I_F): 30 mA. This is the maximum continuous current recommended for reliable long-term operation.
• Reverse Voltage (V_R): 5 V. Exceeding this voltage in reverse bias can cause junction breakdown.
• Operating & Storage Temperature Range: -55°C to +85°C. The device is rated for operation and storage across this wide industrial temperature range.
• Infrared Soldering Condition: Withstands 260°C peak temperature for 10 seconds, compliant with lead-free (Pb-free) reflow soldering profiles.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at Ta=25°C and I_F=20mA, unless stated otherwise.

• Luminous Intensity (I_V): 18.0 - 60.0 mcd (millicandela). The actual intensity is binned (see Section 3). Measurement follows the CIE eye-response curve.
• Viewing Angle (2θ_1/2): 130 degrees. This wide viewing angle indicates a diffuse, non-focused light emission pattern suitable for area illumination.
• Peak Emission Wavelength (λ_P): 588 nm. This is the wavelength at which the spectral power output is maximum.
• Dominant Wavelength (λ_d): 587 nm. Derived from the CIE chromaticity diagram, this single wavelength best represents the perceived color (yellow) of the LED.
• Spectral Line Half-Width (Δλ): 15 nm. This narrow bandwidth is characteristic of AlInGaP LEDs, providing saturated color purity.
• Forward Voltage (V_F): 2.0V (Min), 2.4V (Typ) at 20mA. This parameter is crucial for designing the current-limiting circuitry.
• Reverse Current (I_R): 10 μA (Max) at V_R=5V.
• Capacitance (C): 40 pF (Typ) at V_F=0V, f=1MHz. Relevant for high-speed switching applications.

3. Binning System Explanation

The luminous intensity of the LEDs is sorted into bins to ensure consistency. The bin code defines a minimum and maximum intensity range measured at 20mA. The tolerance within each bin is +/-15%.

• Bin M: 18.0 - 28.0 mcd
• Bin N: 28.0 - 45.0 mcd
• Bin P: 45.0 - 71.0 mcd
• Bin Q: 71.0 - 112.0 mcd
• Bin R: 112.0 - 180.0 mcd

This system allows designers to select LEDs with the required brightness level for their application, ensuring visual uniformity in multi-LED arrays.

4. Performance Curve Analysis

While specific graphs are referenced in the datasheet (e.g., Fig.1, Fig.5), typical curves for such LEDs would include:

• I-V (Current-Voltage) Curve: Shows the exponential relationship between forward voltage and current. The knee voltage is around 2.0-2.4V.
• Luminous Intensity vs. Forward Current: Intensity increases approximately linearly with current up to the maximum rated current.
• Luminous Intensity vs. Ambient Temperature: Intensity typically decreases as ambient temperature increases due to reduced quantum efficiency and increased non-radiative recombination.
• Spectral Distribution: A plot showing light output versus wavelength, peaking at 588nm with a 15nm half-width.
• Viewing Angle Pattern: A polar diagram illustrating the 130-degree full viewing angle where intensity falls to half of its on-axis value.

5. Mechanical & Packaging Information

The LED comes in a standard SMD package. The datasheet includes detailed dimensioned drawings (in mm) for the component itself. Key mechanical notes include:

• Tolerance on most dimensions is ±0.10mm.
• The package is designed for reverse mounting.
• Suggested solder pad dimensions are provided to ensure a reliable solder joint and proper alignment during reflow.
• Polarity is indicated on the device, which is critical for correct installation.

5.1 Tape and Reel Packaging

The LEDs are supplied on 8mm carrier tape sealed with a top cover tape, wound onto 7-inch (178mm) diameter reels.

• Quantity per Reel: 3000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Packaging Standards: Complies with ANSI/EIA-481 specifications.
• Missing Components: A maximum of two consecutive empty pockets is allowed per reel standard.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profile

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

• Pre-heat: 150-200°C.
• Pre-heat Time: Maximum 120 seconds.
• Peak Temperature: Maximum 260°C.
• Time Above Liquidus (at peak): Maximum 10 seconds. The LED should not be subjected to reflow more than twice.

The profile is based on JEDEC standards. Designers must characterize their specific PCB assembly process, considering board design, solder paste, and oven characteristics.

6.2 Hand Soldering

If hand soldering is necessary:

• Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per lead.
• Limit to one soldering cycle only.

6.3 Cleaning

If cleaning after soldering is required:

• Use only specified solvents: ethyl alcohol or isopropyl alcohol at normal temperature.
• Immersion time should be less than one minute.
• Unspecified chemicals may damage the LED package.

6.4 Storage Conditions

• Sealed Package (with desiccant): Store at ≤30°C and ≤90% RH. Use within one year.
• Opened Package: Store at ≤30°C and ≤60% RH. For components removed from moisture-proof packing, it is recommended to complete IR reflow within 672 hours (28 days, MSL 2a).
• Extended Storage (out of bag): Store in a sealed container with desiccant or in a nitrogen desiccator. If stored for >672 hours, bake at 60°C for at least 20 hours before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

7. Application Suggestions & Design Considerations

7.1 Typical Application Scenarios

• Status Indicators: On consumer electronics, appliances, and networking equipment.
• Backlighting: For keys on keypads, membrane switches, or small LCD panels.
• Automotive Interior Lighting: For dashboard icons, switch illumination, or ambient lighting.
• Industrial Panel Indicators: Providing clear visual status in control panels.

7.2 Drive Method and Circuit Design

LEDs are current-operated devices. To ensure stable light output and long lifetime:

• Always use a current-limiting resistor or a constant-current driver. Do not connect directly to a voltage source.
• Calculate the series resistor using: R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet for a conservative design.
• For example, with a 5V supply and targeting I_F=20mA: R = (5V - 2.4V) / 0.02A = 130 Ω. A standard 130Ω or 150Ω resistor would be suitable.
• For PWM (Pulse Width Modulation) dimming, ensure the frequency is high enough (>100Hz) to avoid visible flicker.

7.3 Electrostatic Discharge (ESD) Precautions

LEDs are sensitive to ESD. Always follow these precautions during handling and assembly:

• Use a grounded wrist strap or anti-static gloves.
• Ensure all workstations, tools, and machinery are properly grounded.
• Store and transport LEDs in ESD-safe packaging.

8. Technical Comparison & Differentiation

Compared to traditional through-hole LEDs or other SMD types, this device offers several advantages:

• Reverse Mount Design: Offers flexibility for optical design where the light-emitting surface needs to be closer to the PCB or for specific light extraction angles.
• AlInGaP Technology: Provides higher efficiency and better temperature stability compared to older technologies like GaAsP, resulting in brighter and more consistent yellow light output.
• Full SMD Compatibility: The tape-and-reel packaging and compatibility with IR reflow enable high-speed, low-cost automated assembly, reducing manufacturing time and potential for manual error.
• Wide Viewing Angle: The 130-degree angle provides broad, even illumination rather than a narrow beam, ideal for indicator applications.

9. Frequently Asked Questions (FAQs)

Q1: What is the difference between peak wavelength (588nm) and dominant wavelength (587nm)?
A1: Peak wavelength is the physical point of maximum spectral output. Dominant wavelength is a calculated value from colorimetry that best matches the human eye's perception of the color. They are often very close for monochromatic LEDs like this one.

Q2: Can I drive this LED at 30mA continuously?
A2: Yes, 30mA is the maximum rated DC forward current. However, for optimal longevity and to account for elevated ambient temperatures, driving it at or below the typical 20mA is recommended. Always consider thermal management on the PCB.

Q3: What does "reverse mount" mean?
A3: In a standard SMD LED, the lens faces away from the PCB. In a reverse mount design, the LED is intended to be mounted with the lens facing towards the PCB. This often requires a hole or aperture in the PCB for the light to escape, allowing for unique optical integration.

Q4: How do I interpret the bin code in the part number?
A4: The bin code (e.g., KSKT) is not fully detailed in the excerpt but typically corresponds to specific ranges of luminous intensity and sometimes chromaticity. The separate bin list (M, N, P, Q, R) provided is used to specify the intensity grade ordered. Consult the full manufacturer's binning document for the exact mapping of the part number suffix.

10. Practical Design Case Study

Scenario: Designing a low-power, yellow status indicator for a portable device powered by a 3.3V microcontroller rail.

Design Steps:

1. Current Selection: Choose a drive current of 10mA for low power consumption while maintaining good visibility. According to typical curves, luminous intensity at 10mA will be roughly proportional to the current (approx. half of the 20mA value).
2. Resistor Calculation: Using typical V_F = 2.4V and supply = 3.3V. R = (3.3V - 2.4V) / 0.01A = 90 Ω. The nearest standard value is 91 Ω.
3. Power Dissipation Check: Power in LED: P_LED = V_F * I_F = 2.4V * 0.01A = 24 mW, well below the 75 mW maximum. Power in resistor: P_R = (0.01A)^2 * 91Ω = 9.1 mW.
4. PCB Layout: Follow the suggested solder pad dimensions from the datasheet. Ensure the polarity marking on the footprint matches the LED's cathode marking. If using the reverse mount feature, design a suitable aperture in the PCB under the LED location.
5. ESD & Assembly: Specify ESD precautions in the assembly guide. Use the recommended reflow profile parameters as a starting point for process qualification.

11. Technology Principle Introduction

The LED is based on AlInGaP semiconductor material grown on a substrate. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the active region where they recombine. In a direct bandgap material like AlInGaP, this recombination releases energy in the form of photons (light). The specific wavelength of yellow light (~587-588 nm) is determined by the bandgap energy of the AlInGaP alloy composition. The water-clear epoxy lens encapsulates the chip, providing mechanical protection, shaping the light output (130-degree viewing angle), and enhancing light extraction efficiency.

12. Industry Trends

The market for SMD LEDs continues to evolve towards:

• Higher Efficiency: More lumens per watt (lm/W), reducing energy consumption for the same light output.
• Miniaturization: Smaller package sizes (e.g., 0402, 0201) enabling higher density on PCBs.
• Improved Color Consistency: Tighter binning tolerances for both intensity and chromaticity coordinates, critical for applications requiring uniform appearance.
• Enhanced Reliability: Better performance under high temperature and humidity, extending operational lifetime in demanding environments like automotive.
• Integrated Solutions: LEDs with built-in current limiting resistors, Zener diodes for ESD protection, or even driver ICs, simplifying circuit design.

This reverse-mount AlInGaP LED represents a mature and reliable solution within this broader trend, offering a balance of performance, cost, and manufacturability for a wide range of indicator applications.