Reverse Mount SMD LED LTST-C216TBKT Datasheet - Blue - 2.8-3.8V - 76mW - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a high-performance, reverse mount surface-mount device (SMD) LED emitting blue light. The component is designed for automated assembly processes and is compliant with RoHS and green product standards. Its primary application is in electronic equipment requiring reliable, compact light sources.

1.1 Core Features and Advantages

The LED offers several key advantages for modern electronics manufacturing:

• Environmental Compliance: The product meets RoHS (Restriction of Hazardous Substances) directives and is classified as a green product.
• Reverse Mount Design: This specific package style is optimized for applications where the LED is mounted with the lens facing away from the circuit board, often for side-firing or edge-lighting effects.
• Manufacturing Compatibility: It is supplied in standard 8mm tape on 7-inch diameter reels, making it fully compatible with high-speed automatic pick-and-place equipment used in volume production.
• Process Compatibility: The device is designed to withstand standard infrared (IR) reflow, vapor phase reflow, and wave soldering processes, offering flexibility in assembly line setup.
• Standardization: It conforms to EIA (Electronic Industries Alliance) standard package dimensions, ensuring interchangeability and ease of design.
• Drive Simplicity: The LED is I.C. (Integrated Circuit) compatible, meaning it can be easily driven by standard logic-level outputs with appropriate current limiting.

2. Technical Specifications Deep Dive

This section provides a detailed, objective analysis of the LED's key parameters, derived from the Absolute Maximum Ratings and Electrical/Optical Characteristics tables.

2.1 Absolute Maximum Ratings

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

• Power Dissipation (Pd): 76 mW. This is the maximum amount of power the LED package can dissipate as heat at an ambient temperature (Ta) of 25°C. Exceeding this will cause excessive junction temperature rise.
• DC Forward Current (IF): 20 mA. The maximum continuous forward current recommended for reliable operation.
• Peak Forward Current: 100 mA. This is permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to achieve higher instantaneous light output without overheating.
• Derating: The DC forward current must be linearly derated by 0.25 mA for every degree Celsius the ambient temperature rises above 50°C. For example, at 70°C, the maximum continuous current would be 20 mA - (0.25 mA/°C * 20°C) = 15 mA.
• Reverse Voltage (VR): 5 V maximum. Applying a reverse voltage higher than this can cause immediate and catastrophic failure. The datasheet explicitly notes that reverse voltage cannot be used for continuous operation.
• Temperature Ranges: The device can operate and be stored within a wide temperature range of -55°C to +85°C.
• Soldering Tolerance: The LED can withstand soldering temperatures of 260°C for up to 5 seconds (IR/Wave) or 215°C for up to 3 minutes (Vapor Phase), defining the process window for PCB assembly.

2.2 Electrical and Optical Characteristics

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

• Luminous Intensity (Iv): Ranges from a minimum of 28.0 mcd to a maximum of 180.0 mcd. The actual value for a specific unit depends on its bin code (see Section 3). Intensity is measured using a sensor filtered to match the human eye's photopic response (CIE curve).
• Viewing Angle (2θ1/2): 130 degrees. This wide viewing angle indicates a Lambertian or near-Lambertian emission pattern, suitable for applications requiring broad, even illumination rather than a focused beam.
• Peak Wavelength (λP): Typically 468 nm. This is the wavelength at which the spectral power output is highest.
• Dominant Wavelength (λd): Ranges from 465.0 nm to 475.0 nm. This is the single wavelength perceived by the human eye that defines the color (blue). It is calculated from the CIE chromaticity coordinates.
• Spectral Line Half-Width (Δλ): Approximately 25 nm. This specifies the bandwidth of the emitted light, measured as the full width at half maximum (FWHM) of the spectral peak.
• Forward Voltage (VF): Ranges from 2.80 V to 3.80 V at 20 mA. The exact value is binned (see Section 3). This parameter is critical for designing the current-limiting resistor in the drive circuit.
• Reverse Current (IR): Maximum of 10 μA when a 5V reverse bias is applied. A higher than specified leakage current may indicate damage.
• Capacitance (C): Typically 40 pF measured at 0V bias and 1 MHz frequency. This is generally negligible for most DC and low-frequency applications but could be relevant in high-speed multiplexing circuits.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into bins based on key parameters. This allows designers to select parts that meet specific application requirements for color and brightness uniformity.

3.1 Forward Voltage Binning

Units are sorted by their forward voltage drop at 20 mA. Bins D7 through D11 cover the range from 2.80V to 3.80V in 0.2V steps, with a tolerance of ±0.1V within each bin. Selecting LEDs from the same voltage bin helps ensure uniform current sharing when multiple devices are connected in parallel.

3.2 Luminous Intensity Binning

This binning categorizes LEDs by their light output. Bins N, P, Q, and R cover intensity ranges from 28-45 mcd, 45-71 mcd, 71-112 mcd, and 112-180 mcd, respectively. Each bin has a tolerance of ±15%. Choosing parts from a single intensity bin is crucial for applications requiring consistent brightness across multiple indicators.

3.3 Dominant Wavelength Binning

This defines the perceived color. For this blue LED, bins AC (465-470 nm) and AD (470-475 nm) are available, with a tight tolerance of ±1 nm per bin. This ensures minimal color variation in multi-LED arrays.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Fig.1, Fig.6), their typical implications are analyzed here.

4.1 Luminous Intensity vs. Forward Current (I-V Curve)

The light output (luminous intensity) of an LED is directly proportional to the forward current, up to a point. Operating at the recommended 20 mA ensures optimal efficiency and longevity. The 100 mA pulsed rating allows for brief periods of overdrive for strobe or high-brightness signaling applications, but continuous operation at such currents would violate the power dissipation rating.

4.2 Temperature Dependence

LED performance is temperature-sensitive. The forward voltage typically decreases with increasing junction temperature. More importantly, luminous intensity decreases as temperature rises. The derating specification for forward current (0.25 mA/°C above 50°C) is a direct consequence of this thermal management requirement, preventing the junction temperature from exceeding safe limits.

4.3 Spectral Characteristics

The spectral distribution curve (referenced by peak wavelength measurement) shows the intensity of light emitted at each wavelength. The dominant wavelength (λd) is derived from this curve and the CIE color space. The 25 nm spectral half-width indicates a relatively pure blue color. The peak wavelength may shift slightly with changes in drive current and temperature.

5. Mechanical and Packaging Information

5.1 Package Dimensions and Polarity

The LED conforms to a standard EIA SMD package outline. The datasheet includes a detailed dimensional drawing (all dimensions in mm). For reverse mount packages, identifying the cathode/anode orientation from the top view is critical. Typically, a marking on the package or an asymmetric feature indicates the cathode. The suggested soldering pad layout diagram ensures proper solder joint formation and mechanical stability during reflow.

5.2 Tape and Reel Specifications

The component is supplied in industry-standard 8mm carrier tape wound on 7-inch reels. Key packaging notes include: 3000 pieces per reel, a minimum pack quantity of 500 for remainders, and a maximum of two consecutive missing components allowed per reel. The packaging follows ANSI/EIA 481-1-A-1994 standards, ensuring compatibility with automated feeders.

6. Soldering and Assembly Guidelines

6.1 Recommended Reflow Profiles

The datasheet provides suggested infrared (IR) reflow profiles for both normal (tin-lead) and Pb-free solder processes. Key parameters include pre-heat zones, time above liquidus, and peak temperature (max 260°C for 5 seconds). Adhering to these profiles is essential to prevent thermal shock, which can cause package cracking or delamination, and to ensure reliable solder joints without damaging the LED chip.

6.2 Storage and Handling

Storage: LEDs should be stored in conditions not exceeding 30°C and 70% relative humidity. Components removed from their original moisture-barrier bag should be reflow-soldered within one week. For longer storage outside the bag, they must be kept in a sealed container with desiccant or in a nitrogen atmosphere. If stored unpacked for over a week, a 24-hour bake at 60°C is required before soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

Cleaning: If post-solder cleaning is necessary, only alcohol-based solvents like isopropyl alcohol or ethyl alcohol should be used. The LED should be immersed at normal temperature for less than one minute. Other unspecified chemicals may damage the epoxy lens or package.

6.3 ESD (Electrostatic Discharge) Precautions

LEDs are sensitive to electrostatic discharge. Handling must be done with proper ESD controls: using grounded wrist straps, anti-static gloves, and ensuring all equipment and work surfaces are properly grounded. A power surge can also cause immediate failure.

7. Application Notes and Design Considerations

7.1 Intended Use and Limitations

This LED is designed for ordinary electronic equipment in office, communications, and household applications. It is not recommended for safety-critical applications (aviation, medical life-support, transportation control) without prior consultation and qualification, as failure could jeopardize life or health.

7.2 Drive Circuit Design

An LED is a current-driven device. The most reliable method to drive multiple LEDs is to use a series current-limiting resistor for each LED (Circuit Model A). Connecting LEDs directly in parallel (Circuit Model B) is not recommended because small variances in forward voltage (VF) between individual units will cause significant imbalance in current distribution, leading to uneven brightness and potential overstress of the LED with the lowest VF.

The series resistor value (R) is calculated using Ohm's Law: R = (Vsupply - VF) / IF, where VF is the forward voltage of the LED (use max value from bin for reliability) and IF is the desired forward current (e.g., 20 mA).

7.3 Thermal Management

Although power dissipation is low (76 mW), proper thermal design on the PCB is still important, especially when operating at high ambient temperatures or when multiple LEDs are placed close together. Ensuring adequate copper area around the solder pads helps dissipate heat and maintain lower junction temperatures, which preserves light output and device lifetime.

8. Technical Comparison and Trends

8.1 Differentiation

The key differentiator for this product is its reverse mount configuration. Unlike standard top-emitting SMD LEDs, this package is designed to be mounted with the primary light emission parallel to the PCB surface. This is ideal for light-guide applications, edge-lit panels, and status indicators where the light needs to be directed sideways.

8.2 Technology and Trends

This LED uses an InGaN (Indium Gallium Nitride) semiconductor material, which is the standard for producing high-efficiency blue and green LEDs. The technology is mature and offers excellent reliability and performance. Industry trends continue to focus on increasing luminous efficacy (more light output per watt), improving color consistency through tighter binning, and enhancing compatibility with lead-free (Pb-free) and high-temperature soldering processes required for modern, dense PCB assemblies.

9. Frequently Asked Questions (FAQ)

9.1 Can I drive this LED without a current-limiting resistor?

No. Connecting an LED directly to a voltage source is a common cause of immediate failure. The forward voltage is not a fixed threshold but a characteristic curve. A small increase in voltage above VF causes a large, potentially destructive increase in current. A series resistor (or a constant-current driver) is mandatory.

9.2 Why is there such a wide range in luminous intensity (28-180 mcd)?

This range represents the total spread across all production. Through the binning system (N, P, Q, R), manufacturers sort LEDs into much tighter groups. For consistent brightness in your application, you should specify and purchase LEDs from a single intensity bin.

9.3 What is the difference between peak wavelength and dominant wavelength?

Peak Wavelength (λP) is the physical wavelength where the LED emits the most optical power. Dominant Wavelength (λd) is a calculated value based on how the human eye perceives color. For a monochromatic blue LED like this one, they are often close, but λd is the more relevant parameter for color matching.

9.4 How do I interpret the soldering profile graphs?

The graphs plot temperature on the Y-axis against time on the X-axis. They define a safe thermal pathway for the LED during reflow. The profile includes a gradual pre-heat ramp to minimize thermal stress, a controlled time above the solder's melting point to ensure good wetting, and a peak temperature limit (260°C) to prevent damage. The cooling rate is also controlled. Your reflow oven should be programmed to match this suggested profile.