LTL-R42FKFD LED Lamp Datasheet - T-1 Diameter - Amber Diffused - 2.05V - 20mA - English Technical Document

1. Product Overview

The LTL-R42FKFD is a through-hole mounted LED lamp designed for status indication and signaling applications across various electronic devices. It belongs to the T-1 package family, characterized by its cylindrical shape, making it suitable for standard PCB mounting. The device utilizes an AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material for its orange light-emitting chip, which is encapsulated within an amber-colored diffused epoxy lens. This diffusion provides a wide, uniform viewing angle, making the LED easily visible from multiple directions, a key requirement for indicator applications.

The core advantages of this LED include its design for straightforward circuit board assembly, low power consumption coupled with high luminous efficiency, and compliance with environmental standards such as being lead-free and RoHS compliant. Its primary target markets encompass communication equipment, computer peripherals, consumer electronics, and home appliances where reliable, long-lasting visual feedback is necessary.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the LED may occur. They are specified at an ambient temperature (TA) of 25°C. The maximum continuous power dissipation is 75 mW. The DC forward current should not exceed 30 mA under normal operation. For pulsed operation, a peak forward current of 60 mA is permissible under strict conditions: a duty cycle of 10% or less and a pulse width not exceeding 10 milliseconds. The device can operate within a temperature range of -30°C to +85°C and be stored between -40°C and +100°C. A critical parameter for assembly is the lead soldering temperature, rated at 260°C for a maximum of 5 seconds when measured 2.0mm from the LED body.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured at TA=25°C and a forward current (IF) of 20 mA, which is the standard test condition. The luminous intensity (Iv) has a typical value of 400 millicandelas (mcd), with a minimum of 140 mcd and a maximum of 680 mcd. It is crucial to note that the guarantee for Iv includes a ±30% testing tolerance. The viewing angle (2θ1/2), defined as the full angle where intensity drops to half its axial value, is 65 degrees, indicating a moderately wide beam.

The dominant wavelength (λd), which defines the perceived color, ranges from 597 nm to 612 nm, placing it firmly in the amber/orange region of the spectrum. The peak emission wavelength (λp) is typically 611 nm. The forward voltage (VF) typically measures 2.05V, with a range from 1.6V to 2.4V at 20mA. The reverse current (IR) is very low, with a maximum of 10 μA at a reverse voltage (VR) of 5V. It is explicitly stated that the device is not designed for reverse operation; this test condition is for characterization only.

3. Bin Table Specification

The product is sorted into bins based on two key parameters to ensure consistency within a production lot. This allows designers to select LEDs with specific performance characteristics.

3.1 Luminous Intensity Binning

LEDs are classified into three intensity bins at IF=20mA: Bin GH (140-240 mcd), Bin JK (240-400 mcd), and Bin LM (400-680 mcd). The tolerance for each bin limit is ±30%.

3.2 Dominant Wavelength Binning

LEDs are also binned by their dominant wavelength into five categories: H22 (597.0-600.0 nm), H23 (600.0-603.0 nm), H24 (603.0-606.5 nm), H25 (606.5-610.0 nm), and H26 (610.0-612.0 nm). The tolerance for each wavelength bin limit is ±1 nm. The bin codes for both intensity and wavelength are marked on the product packaging, enabling precise selection for color- and brightness-critical applications.

4. Performance Curve Analysis

The datasheet references typical curves that illustrate the relationship between key parameters. While the specific graphs are not reproduced in the text, their implications are standard. These typically include the Relative Luminous Intensity vs. Forward Current curve, which shows how light output increases with current, usually in a near-linear fashion until efficiency drops at higher currents. The Forward Voltage vs. Forward Current curve demonstrates the diode's exponential I-V characteristic. The Relative Luminous Intensity vs. Ambient Temperature curve is critical, showing the decrease in light output as the junction temperature rises. For AlInGaP LEDs, this derating is significant. The Spectral Distribution graph would show the concentration of emitted light around the 611 nm peak with a spectral half-width of 17 nm.

5. Mechanical and Package Information

5.1 Outline Dimensions

The LED features a standard T-1 (3mm) diameter package. Key dimensional notes include: all dimensions are in millimeters (with inch equivalents), standard tolerance is ±0.25mm unless specified otherwise, the maximum protrusion of resin under the flange is 1.0mm, and lead spacing is measured where the leads emerge from the package body. The physical drawing would show the cylindrical lens, the flange for seating against the PCB, and the two axial leads.

5.2 Polarity Identification

For through-hole LEDs, polarity is typically indicated by lead length (the longer lead is the anode, or positive side) and sometimes by a flat spot on the lens flange near the cathode (negative side). Proper orientation is essential as reverse voltage above 5V can damage the device.

6. Soldering and Assembly Guidelines

6.1 Lead Forming

If leads need to be bent for PCB 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 to avoid stressing the heated package.

6.2 Soldering Parameters

Two soldering methods are addressed. For hand soldering with an iron: temperature should not exceed 350°C, soldering time per lead should be 3 seconds maximum (one time only), and the soldering point must be no closer than 2mm from the base of the epoxy lens. For wave soldering: pre-heat temperature should be max 120°C for up to 100 seconds, the solder wave temperature should be max 260°C, contact time should be max 5 seconds, and the dipping position should be no lower than 2mm from the lens base. Crucially, IR reflow soldering is stated as unsuitable for this through-hole type product. Excessive temperature or time can deform the lens or cause catastrophic failure.

6.3 Storage and Handling

For storage, the ambient should not exceed 30°C or 70% relative humidity. LEDs removed from their original moisture-barrier packaging are recommended to be used within three months. For longer storage outside the original bag, they should be kept in a sealed container with desiccant or in a nitrogen ambient. Isopropyl alcohol is recommended for cleaning if necessary.

7. Packaging and Ordering Information

The standard packing specification is tiered: 1000, 500, 200, or 100 pieces per anti-static moisture-barrier bag. Ten of these bags are packed into an inner carton, totaling 10,000 pieces. Eight inner cartons are then packed into a master outer shipping carton, resulting in a total of 80,000 pieces per outer carton. The datasheet notes that in every shipping lot, only the final pack may be a non-full pack. The part number is LTL-R42FKFD.

8. Application Notes and Design Considerations

8.1 Drive Circuit Design

A fundamental principle is emphasized: LEDs are current-operated devices. To ensure uniform brightness when multiple LEDs are connected in parallel, it is strongly recommended to use a individual current-limiting resistor in series with each LED (Circuit A). Connecting LEDs directly in parallel without individual resistors (Circuit B) is discouraged because small variances in the forward voltage (VF) characteristic of each LED will cause significant differences in current sharing and, consequently, brightness. The resistor value is calculated using Ohm's Law: R = (V_supply - VF_LED) / I_desired, where VF_LED is the typical or maximum forward voltage from the datasheet, and I_desired is the target forward current (e.g., 20mA).

8.2 Electrostatic Discharge (ESD) Protection

The LED is susceptible to damage from electrostatic discharge or power surges. Preventive measures include: operators wearing a conductive wrist strap or anti-static gloves, ensuring all equipment and work surfaces are properly grounded, and using an ionizer to neutralize static charge that may build up on the plastic lens during handling.

8.3 Application Suitability

This LED is suitable for both indoor and outdoor signage, as well as ordinary electronic equipment. Its amber color is highly visible and often used for warning, status, or indication purposes.

9. Technical Comparison and Differentiation

The LTL-R42FKFD, based on AlInGaP technology, offers advantages over older technologies like GaAsP (Gallium Arsenide Phosphide). AlInGaP LEDs generally provide higher luminous efficiency, better temperature stability, and more saturated color purity, particularly in the red, orange, and amber regions. Compared to some modern high-power LEDs, this device is a low-power indicator type, prioritizing reliability, ease of use, and cost-effectiveness for status indication rather than high-flux illumination. Its through-hole design offers mechanical robustness and simplicity for prototyping and production compared to surface-mount devices (SMDs) in some applications.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED at 30mA continuously?
A: While the absolute maximum DC forward current is 30mA, the standard test condition and typical operating point is 20mA. Operating at 30mA may reduce lifetime and increase junction temperature. Always refer to the derating curve and ensure power dissipation (Vf * If) does not exceed 75mW, considering the actual Vf at your operating current.

Q: Why is there a ±30% tolerance on the luminous intensity bin limits?
A: This accounts for measurement variability in production testing. It means an LED labeled in the 240-400 mcd bin (JK) could actually measure between 168 mcd and 520 mcd when tested. Designers must account for this spread in their optical design.

Q: The leads are too long for my PCB. Can I cut them before soldering?
A: Yes, leads can be cut. However, if you need to bend them afterwards, ensure the bending point remains at least 3mm from the lens base as per the lead forming guidelines.

Q: Is a heatsink required?
A: For normal operation at 20mA in open air, a heatsink is not typically required for a single indicator LED. However, if multiple LEDs are densely packed or operated in a high ambient temperature environment, thermal management should be considered.

11. Practical Application Examples

Example 1: Power Indicator on a Consumer Appliance: A single LTL-R42FKFD is connected in series with a suitable resistor to a 5V rail. The resistor is calculated as (5V - 2.05V) / 0.020A = 147.5 Ohms. A standard 150 Ohm resistor would result in a current of ~19.7mA, well within spec. The wide viewing angle ensures the power status is visible from various angles in a room.

Example 2: Multi-LED Status Bar on Industrial Equipment: Five LEDs are used to indicate system status levels (e.g., Off, Standby, Active, Warning, Fault). To ensure uniform brightness, each LED has its own current-limiting resistor connected to a common driver IC or microcontroller pin. Using the binning information, the designer can specify a tight wavelength bin (e.g., H24) for color consistency across the bar.

12. Operating Principle

The LED operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's turn-on voltage (approximately 1.6V for this AlInGaP device) is applied, electrons from the n-type region and holes from the p-type region are injected across the junction. These charge carriers recombine in the active region, releasing energy in the form of photons (light). The specific composition of the AlInGaP semiconductor crystal determines the bandgap energy, which directly defines the wavelength (color) of the emitted light—in this case, amber/orange. The diffused epoxy lens both protects the semiconductor chip and scatters the light to create a wide viewing angle.

13. Technology Trends

While through-hole LEDs like the LTL-R42FKFD remain vital for many applications due to their robustness and ease of manual assembly, the broader industry trend is towards surface-mount device (SMD) packages for automated assembly, higher density, and often better thermal performance. However, through-hole components maintain a strong position in prototyping, educational kits, high-vibration environments, and applications requiring strong mechanical bonds. In terms of materials, AlInGaP technology is mature and highly optimized for the red-amber spectrum. Ongoing development focuses on improving efficiency (lumens per watt), longevity, and color consistency, as well as expanding into new package formats that bridge the gap between traditional through-hole and advanced SMD designs.