LTL-R42FSK6D Yellow LED Lamp Datasheet - T-1 Diameter - 2.6V - 78mW - English Technical Document

1. Product Overview

The LTL-R42FSK6D is a through-hole LED lamp designed for status indication and signaling applications. It features a popular T-1 diameter package, making it versatile for mounting on printed circuit boards (PCBs) or panels. The device utilizes AlInGaP (Aluminum Indium Gallium Phosphide) technology for the yellow light-emitting chip, combined with a yellow diffused lens to produce a uniform, wide-angle light output.

1.1 Core Advantages

• High Efficiency & Low Power Consumption: The AlInGaP material system provides high luminous efficacy, enabling bright output with minimal electrical power.
• High Luminous Intensity: Delivers typical luminous intensity of 400 mcd at a standard drive current of 20mA, ensuring excellent visibility.
• Environmental Compliance: This is a lead (Pb)-free product, fully compliant with the RoHS (Restriction of Hazardous Substances) directive.
• Design Flexibility: The standard T-1 (3mm) package is widely used and compatible with common PCB layouts and panel cutouts.
• Low Current Drive: Compatible with integrated circuit (IC) outputs, requiring only a low forward current for operation, simplifying driver design.

1.2 Target Applications

This LED is suitable for a broad range of electronic equipment requiring clear, reliable visual indicators. Key application areas include:

• Communication Equipment: Status lights on routers, modems, switches.
• Computer Peripherals: Power, HDD activity, and function indicators.
• Consumer Electronics: Indicators on audio/video equipment, home appliances.
• Home Appliances: Power-on, timer, or function status indicators on microwaves, washing machines, etc.
• Industrial Controls: Machine status, fault indicators, and control panel lighting.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation at or near these limits is not recommended.

• Power Dissipation (P_D): 78 mW at an ambient temperature (T_A) of 25°C. This is the maximum power the LED package can safely dissipate as heat.
• DC Forward Current (I_F): 30 mA continuous. The LED should not be operated above this DC current level.
• Peak Forward Current: 60 mA, permissible only under pulsed conditions (duty cycle ≤ 1/10, pulse width ≤ 10 µs). This allows for brief over-current conditions, such as during multiplexing.
• Derating: The maximum allowable DC forward current decreases linearly above 50°C at a rate of 0.43 mA/°C. This is critical for thermal management in high-temperature environments.
• Operating & Storage Temperature: The device can operate from -40°C to +85°C and be stored from -40°C to +100°C.
• Lead Soldering Temperature: 260°C for a maximum of 5 seconds, measured 2.0mm from the LED body. This defines the hand or wave soldering process window.

2.2 Electrical & Optical Characteristics

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

• Luminous Intensity (I_V): 180 mcd (Min), 400 mcd (Typ), 880 mcd (Max). This wide range is managed through a binning system (see Section 4). Intensity is measured with a filter matching the CIE photopic eye-response curve.
• Viewing Angle (2θ_1/2): 65 degrees. This is the full angle at which the luminous intensity drops to half of its on-axis (0°) value. The diffused lens creates this wide viewing cone.
• Peak Emission Wavelength (λ_P): 588 nm. This is the wavelength at which the spectral power distribution is at its maximum.
• Dominant Wavelength (λ_d): 587 nm. This is the single wavelength perceived by the human eye that defines the color (yellow) of the LED, derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): 15 nm. This indicates the spectral purity; a narrower width means a more saturated, pure color.
• Forward Voltage (V_F): 2.0V (Min), 2.6V (Typ), V (Max). The voltage drop across the LED when conducting 20mA. Designers must account for this when calculating series resistor values.
• Reverse Current (I_R): 100 µA (Max) at a reverse voltage (V_R) of 5V. Important: This device is not designed for reverse-bias operation; this parameter is for leakage test purposes only.

3. Binning System Specification

To ensure color and brightness consistency in production, LEDs are sorted into bins. The LTL-R42FSK6D uses two independent binning criteria.

3.1 Luminous Intensity Binning

LEDs are classified based on their measured luminous intensity at 20mA.

Note: Tolerance on each bin limit is ±15%.

3.2 Dominant Wavelength Binning

LEDs are also sorted by their dominant wavelength to control the precise shade of yellow.

Note: Tolerance on each bin limit is ±1 nm. For applications requiring tight color matching (e.g., multi-LED displays), specifying a single wavelength bin is essential.

4. Mechanical & Package Information

4.1 Outline Dimensions

The LED conforms to the standard T-1 (3mm) radial leaded package. Key dimensional notes include:

• All primary dimensions are in millimeters, with a general tolerance of ±0.25mm unless specified otherwise.
• The maximum protrusion of resin under the flange is 0.7mm.
• Lead spacing is measured at the point where the leads exit the package body, which is critical for PCB hole spacing.

5. Soldering & Assembly Guidelines

5.1 Lead Forming

If leads need to be bent for mounting, the bend must be made at least 3mm away from the base of the LED lens. The base of the lead frame should not be used as a fulcrum. Forming must be done at room temperature and before the soldering process.

5.2 Soldering Process

A minimum clearance of 2mm must be maintained between the base of the epoxy lens and the solder point. The lens must never be immersed in solder.

• Hand Soldering (Iron): Maximum temperature 350°C, maximum time 3 seconds per lead. Only one soldering cycle is permitted.
• Wave Soldering: Pre-heat temperature ≤100°C for ≤60 seconds. Solder wave temperature ≤260°C for ≤5 seconds. The LED should be positioned so the solder wave does not come within 2mm of the lens base.
• Critical Warning: Excessive temperature or time can deform the lens or cause catastrophic LED failure. IR reflow soldering is not suitable for this through-hole type LED.

5.3 Storage & Handling

For long-term storage outside the original packaging, it is recommended to store LEDs in a sealed container with desiccant or in a nitrogen ambient. LEDs removed from packaging should ideally be used within three months. The recommended storage environment is ≤30°C and ≤70% relative humidity.

5.4 Cleaning

If cleaning is necessary, use only alcohol-based solvents such as isopropyl alcohol.

6. Application Design Considerations

6.1 Drive Circuit Design

LEDs are current-operated devices. To ensure uniform brightness when driving multiple LEDs, a current-limiting resistor must be used in series with each LED (Circuit A). Connecting LEDs directly in parallel (Circuit B) is not recommended, as slight variations in the forward voltage (V_F) characteristic between individual LEDs will cause significant differences in current sharing and, consequently, brightness.

Circuit A (Recommended): [Vcc] — [Resistor] — [LED] — [GND] (Repeat for each LED).
Circuit B (Not Recommended): [Vcc] — [Resistor] — [LED1 // LED2 // LED3] — [GND].

The series resistor value (R_S) can be calculated using Ohm's Law: R_S = (V_Supply - V_F) / I_F. Using the typical V_F of 2.6V and a desired I_F of 20mA with a 5V supply: R_S = (5V - 2.6V) / 0.020A = 120 Ω. A standard 120Ω resistor with sufficient power rating (P = I²R = 0.048W) would be suitable.

6.2 Thermal Management

While the power dissipation is low, the derating curve must be respected in high ambient temperature applications. If the ambient temperature exceeds 50°C, the maximum allowable DC forward current must be reduced by 0.43 mA for every degree above 50°C. For example, at 70°C ambient, the maximum I_F would be 30 mA - (0.43 mA/°C * (70-50)°C) = 30 mA - 8.6 mA = 21.4 mA.

6.3 Electrostatic Discharge (ESD) Protection

This LED is susceptible to damage from electrostatic discharge. Proper ESD controls must be implemented during handling and assembly:

• Personnel should wear grounded wrist straps or anti-static gloves.
• All workstations, tools, and storage racks must be properly grounded.
• Use an ionizer to neutralize static charge that may accumulate on the plastic lens during handling.

7. Packaging Specifications

The product is available in several standard packaging quantities to suit different production scales:

• Basic Unit: Available in bags of 1000, 500, 200, or 100 pieces.
• Inner Carton: Contains 10 bags, totaling 10,000 pieces.
• Master (Outer) Carton: Contains 8 inner cartons, totaling 80,000 pieces.

Within a shipping lot, only the final pack may contain a non-full quantity.

8. Technical Comparison & Differentiation

The LTL-R42FSK6D, based on its AlInGaP material and specifications, offers distinct advantages:

• vs. Traditional GaAsP Yellow LEDs: AlInGaP technology provides significantly higher luminous efficiency and brightness (luminous intensity) for the same drive current, resulting in lower power consumption for a given light output.
• vs. Broad-Viewing-Angle LEDs: The 65-degree viewing angle, achieved via a diffused lens, offers a good balance between wide visibility and reasonable on-axis intensity, making it suitable for both direct and indirect viewing applications.
• vs. Non-Binned LEDs: The comprehensive binning system for both intensity and wavelength provides designers with predictable performance and color consistency, which is critical for multi-indicator applications or products where aesthetic uniformity is important.

9. Frequently Asked Questions (FAQs)

9.1 Can I drive this LED directly from a 3.3V or 5V microcontroller pin?

No. While the voltage may seem sufficient, an LED must be current-limited. Connecting it directly to a low-impedance voltage source like a microcontroller pin will typically allow excessive current to flow, potentially damaging both the LED and the microcontroller output. Always use a series current-limiting resistor as described in Section 6.1.

9.2 Why is the luminous intensity range so wide (180-880 mcd)?

This is the total production spread. Through the binning process (Section 3.1), LEDs are sorted into tighter groups (HJ, KL, MN). For consistent brightness in your application, you should specify and purchase LEDs from a single intensity bin.

9.3 Is this LED suitable for outdoor use?

The datasheet states it is good for indoor and outdoor signs. The operating temperature range of -40°C to +85°C supports outdoor environments. However, for prolonged outdoor exposure, consider additional environmental protection (e.g., conformal coating on the PCB, sealed enclosures) to guard against moisture and UV degradation, which are not covered by the LED's own specifications.

9.4 What happens if I exceed the absolute maximum ratings?

Operating beyond these limits, even briefly, can cause immediate or latent failure. Exceeding the power dissipation or current can overheat and destroy the semiconductor junction. Exceeding the soldering temperature/time can melt the epoxy lens or damage internal bonds. The device is not guaranteed to function correctly after such stress.

10. Operating Principle & Technology

The LTL-R42FSK6D is based on a semiconductor diode made from AlInGaP (Aluminum Indium Gallium Phosphide) materials. When a forward voltage exceeding the diode's threshold (approximately 2.0V) is applied, electrons and holes are injected into the active region of the semiconductor where they recombine. This recombination process releases energy in the form of photons (light). The specific composition of the AlInGaP layers determines the wavelength (color) of the emitted light, which in this case is in the yellow spectrum (~587 nm). The epoxy package serves to protect the delicate semiconductor chip, act as a lens to shape the light output beam (65-degree viewing angle), and provide the diffused yellow tint.