LTL17KCBH5D Blue LED Datasheet - T-1 5mm Package - 3.2V 20mA - 240mcd - English Technical Document

1. Product Overview

The LTL17KCBH5D is a high-efficiency, blue light-emitting diode (LED) designed for through-hole mounting on printed circuit boards (PCBs). It belongs to the popular T-1 (5mm) package family, making it a standard choice for a wide range of indicator and illumination applications. The device utilizes InGaN (Indium Gallium Nitride) semiconductor technology to produce light at a dominant wavelength of 470 nm, appearing as a diffused blue color.

1.1 Core Advantages

• High Efficiency & Low Power Consumption: Delivers high luminous intensity with minimal electrical input, contributing to energy-efficient designs.
• RoHS Compliant & Lead-Free: Manufactured in compliance with environmental regulations, making it suitable for global markets.
• Standard Package: The T-1 5mm form factor ensures broad compatibility with existing PCB layouts and manufacturing processes.
• Design Flexibility: Available in specific luminous intensity and wavelength bins, allowing for precise selection based on application requirements.

1.2 Target Markets and Applications

This LED is versatile and suitable for status indication, backlighting, and decorative lighting across multiple industries. Primary application areas include:

• Communication Equipment: Status indicators on routers, switches, and modems.
• Computer Peripherals: Power and activity lights on keyboards, external drives, and hubs.
• Consumer Electronics: Indicator lights in audio/video equipment, toys, and appliances.
• Home Appliances: Display and control panel indicators.
• Industrial Controls: Machine status panels, control system indicators, and instrumentation.

2. Technical Parameters: In-Depth Objective Interpretation

2.1 Absolute Maximum Ratings

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

• Power Dissipation (Pd): 108 mW maximum. This is the total power (Forward Voltage x Forward Current) the LED package can dissipate as heat at an ambient temperature (TA) of 25°C.
• DC Forward Current (IF): 30 mA maximum continuous current.
• Peak Forward Current: 100 mA, permissible only under pulsed conditions (duty cycle ≤ 1/10, pulse width ≤ 10ms) to handle brief surges.
• Derating: The maximum allowable DC forward current decreases linearly by 0.5 mA for every 1°C increase in ambient temperature above 30°C. This is critical for thermal management in enclosed or high-temperature environments.
• Operating & Storage Temperature: The device can operate from -30°C to +80°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 process window for hand or wave soldering.

2.2 Electro-Optical Characteristics

These parameters are measured at TA=25°C and IF=20mA, representing typical operating conditions.

• Luminous Intensity (Iv): 240 mcd (typical). This is the perceived brightness of the LED as seen by the human eye. The actual shipped product is binned with minimum values ranging from 180 mcd to 520 mcd (see Bin Table). A ±15% testing tolerance applies to these values.
• Viewing Angle (2θ1/2): 50 degrees (typical). This is the full angle at which the light intensity drops to half of its peak (on-axis) value. A 50° angle provides a relatively focused beam suitable for directed indication.
• Peak Wavelength (λp): 468 nm (typical). The specific wavelength where the emitted optical power is highest.
• Dominant Wavelength (λd): 470 nm (typical), binned from 460 nm to 475 nm. This is the single wavelength that best represents the perceived color of the light, derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): 22 nm (typical). This indicates the spectral purity or bandwidth of the emitted blue light.
• Forward Voltage (VF): 3.2 V (typical), ranging from 2.7 V to 3.6 V at 20mA. This is the voltage drop across the LED when operating.
• Reverse Current (IR): 100 μA maximum at a Reverse Voltage (VR) of 5V. Important: This LED is not designed for reverse-bias operation; this test condition is for characterization only.

3. Binning System Specification

To ensure consistency in brightness and color for production applications, LEDs are sorted into bins.

3.1 Luminous Intensity Binning

Unit: millicandela (mcd) @ IF = 20mA. The bin code is marked on the packing bag.

• Bin HJ: 180 mcd (Min) to 310 mcd (Max)
• Bin KL: 310 mcd (Min) to 520 mcd (Max)
• Bin MN: 520 mcd (Min) to 880 mcd (Max)

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

3.2 Dominant Wavelength Binning

Unit: nanometer (nm) @ IF = 20mA.

• Bin B07: 460.0 nm (Min) to 465.0 nm (Max)
• Bin B08: 465.0 nm (Min) to 470.0 nm (Max)
• Bin B09: 470.0 nm (Min) to 475.0 nm (Max)

4. Performance Curve Analysis

Typical performance curves (not reproduced in detail here but referenced in the datasheet) provide visual guidance for designers. These typically include:

• Relative Luminous Intensity vs. Forward Current: Shows how brightness increases with current, up to the maximum rating.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the thermal quenching effect, where light output decreases as junction temperature rises.
• Forward Voltage vs. Forward Current: Illustrates the non-linear I-V characteristic of the diode.
• Spectral Distribution: A graph showing the relative power emitted across different wavelengths, centered around the peak wavelength.

These curves are essential for predicting performance under non-standard conditions (e.g., different drive currents or ambient temperatures).

5. Mechanical and Package Information

5.1 Outline Dimensions

The LED has a standard T-1 5mm round lens. Key dimensions include:

• Lens Diameter: 5.4 mm (0.212 inches) maximum.
• Package Height: 8.6 mm (0.339 inches) from the bottom of the leads to the top of the lens.
• Lead Diameter: 0.5 mm ±0.05 mm (0.0197 ±0.002 inches).
• Lead Spacing: 2.54 mm (0.1 inches) nominal, measured where leads emerge from the package.
• Cathode Identifier: The cathode lead is typically identified by a flat spot on the lens flange or a shorter lead (check manufacturer marking). The provided diagram indicates the cathode side.

Important Notes: Tolerance is ±0.25mm unless specified. A maximum of 1.0mm of protruded resin under the flange is allowed. Lead forming and soldering must maintain minimum distances from the LED body as specified in the Cautions section.

6. Soldering and Assembly Guidelines

6.1 Storage and Handling

• Store in an environment not exceeding 30°C and 70% relative humidity.
• Use within three months if removed from original moisture-barrier packaging. For longer storage, use a sealed container with desiccant or a nitrogen ambient.
• Handle with ESD precautions: use grounded wrist straps, workstations, and ionizers to neutralize static on the lens.
• Clean only with alcohol-based solvents like isopropyl alcohol if necessary.

6.2 Lead Forming and PCB Mounting

• Bend leads at a point at least 3mm from the base of the LED lens.
• Do not use the LED body as a fulcrum during bending.
• Perform all lead forming at room temperature and before soldering.
• Apply minimum clinch force during PCB insertion to avoid mechanical stress.

6.3 Soldering Process

Maintain a minimum distance of 3mm (for iron) or 2mm (for wave) between the solder point and the base of the lens. Never immerse the lens in solder.

• Soldering Iron: Max temperature 350°C, max time 3 seconds per lead (one time only).
• Wave Soldering: Pre-heat to max 100°C for up to 60 seconds. Solder wave at max 260°C for up to 5 seconds.
• Critical: Infrared (IR) reflow soldering is not suitable for this through-hole LED product. Excessive heat or time can deform the lens or cause failure.

7. Packaging and Ordering Information

7.1 Packaging Specification

The LEDs are packed in anti-static bags to prevent ESD damage during transport and handling.

• 500 pieces per packing bag.
• 10 packing bags per inner carton (5,000 pieces total).
• 8 inner cartons per master outer carton (40,000 pieces total).
• In a shipping lot, only the final pack may contain a non-full quantity.

8. Application Design Recommendations

8.1 Drive Circuit Design

LEDs are current-driven devices. To ensure uniform brightness and prevent over-current damage, a current-limiting resistor must be used in series with each LED.

• Recommended Circuit (Circuit A): Use a separate resistor for each LED, connected in series. This compensates for the natural variation in forward voltage (VF) from one LED to another, ensuring each receives the same current and thus has similar brightness.
• Not Recommended (Circuit B): Connecting multiple LEDs directly in parallel with a single shared resistor is discouraged. Small differences in VF will cause current to divide unevenly, leading to significant differences in brightness between LEDs.

The resistor value (R) can be calculated using Ohm's Law: R = (Vsupply - VF_LED) / IF, where IF is the desired forward current (e.g., 20mA).

8.2 Thermal Management Considerations

While the power dissipation is low, the derating specification must be respected in high ambient temperature applications. Ensure adequate airflow or heatsinking if the LED is driven at or near its maximum current in an environment above 30°C. The linear derating of 0.5 mA/°C above 30°C directly impacts the maximum safe operating current.

8.3 Optical Design

The 50-degree viewing angle provides a directed beam. For wider illumination, secondary optics like diffusers or light pipes may be employed. The blue diffused lens helps in achieving a more uniform appearance from different viewing angles compared to a clear lens.

9. Technical Comparison and Differentiation

Compared to older technology like GaP (Gallium Phosphide) blue LEDs, this InGaN-based device offers significantly higher luminous efficiency and a more saturated blue color. Within the T-1 5mm blue LED category, key differentiators for the LTL17KCBH5D include its specific binning structure for intensity and wavelength, its clearly defined maximum ratings and derating curve, and its detailed handling and soldering cautions, which aid in reliable manufacturing.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 Can I drive this LED at 30mA continuously?

Yes, but only if the ambient temperature (TA) is at or below 30°C. If TA is higher, you must reduce the current according to the derating factor of 0.5 mA/°C above 30°C to avoid exceeding the maximum junction temperature and degrading reliability.

10.2 Why is a separate resistor needed for each LED in parallel?

Due to manufacturing tolerances, the forward voltage (VF) of LEDs varies. Without individual resistors, LEDs with a slightly lower VF will draw disproportionately more current, becoming brighter and potentially overheating, while those with higher VF will be dimmer. Series resistors ensure current equalization.

10.3 What is the difference between Peak Wavelength and Dominant Wavelength?

Peak Wavelength (λp) is the physical wavelength where the optical output power is greatest. Dominant Wavelength (λd) is a calculated value based on human color perception (CIE chart) that best represents the color we see. For monochromatic LEDs like this blue one, they are often close, but λd is the more relevant parameter for color specification.

10.4 Can I use this LED for outdoor applications?

The datasheet states it is suitable for indoor and outdoor signs. However, for harsh outdoor environments, consider additional protection such as conformal coating on the PCB, UV-stable lenses if exposed to direct sunlight for long periods, and ensuring the operating temperature range (-30°C to +80°C) is not exceeded.

11. Practical Design and Usage Case

Scenario: Designing a multi-indicator panel for a network switch. The panel requires ten uniform blue status lights. The system power rail is 5V.

1. Component Selection: Specify LTL17KCBH5D LEDs from the same intensity bin (e.g., KL) and wavelength bin (e.g., B08) to guarantee visual consistency.
2. Circuit Design: Design ten identical drive circuits. For a target current of 20mA and a typical VF of 3.2V, calculate the series resistor: R = (5V - 3.2V) / 0.020A = 90 Ohms. Use a standard 91 Ohm or 100 Ohm resistor. Place one resistor in series with each LED anode.
3. PCB Layout: Follow the dimensional drawing for hole spacing (2.54mm). Ensure the cathode (identified lead) is correctly oriented on the PCB silkscreen. Maintain the recommended 3mm clearance between the LED body and the solder pad.
4. Assembly: Insert LEDs, form leads gently 3mm from the body if needed, and wave solder using the specified profile (max 260°C for 5s, pre-heat).
5. Result: A panel with ten consistently bright and uniformly colored blue indicators, ensuring reliable long-term operation.

12. Operating Principle Introduction

This LED operates on the principle of electroluminescence in a semiconductor p-n junction. The active region is composed of InGaN. When a forward voltage exceeding the diode's threshold is applied, electrons from the n-type region and holes from the p-type region are injected into the active region. There, they recombine, releasing energy in the form of photons (light). The specific composition of the InGaN alloy determines the bandgap energy, which in turn defines the wavelength (color) of the emitted light—in this case, blue at around 470 nm. The epoxy lens serves to protect the semiconductor chip, shape the light output beam, and provide mechanical support for the leads.

13. Technology Trends

The development of high-brightness blue LEDs based on InGaN was a foundational achievement in solid-state lighting, enabling the creation of white LEDs (via phosphor conversion) and full-color displays. Current trends in indicator-type LEDs include:

• Miniaturization: Movement towards smaller surface-mount device (SMD) packages like 0402 and 0201, though through-hole packages remain vital for robustness, serviceability, and certain applications.
• Increased Efficiency: Ongoing improvements in internal quantum efficiency and light extraction from the package lead to higher luminous intensity per unit of electrical input.
• Integrated Solutions: Growth of LEDs with built-in current-limiting resistors or IC drivers for simplified circuit design.
• Color Consistency: Tighter binning specifications and advanced manufacturing controls to reduce color and brightness variation within a production batch.

Through-hole LEDs like the LTL17KCBH5D continue to be relevant due to their ease of use, reliability, and cost-effectiveness for prototyping, education, and applications where manual assembly or high mechanical strength is required.