SMD LED LTST-N682TWQEET Datasheet - Package Dimensions - White/Red - 30mA - English Technical Document

1. Product Overview

This document provides the technical specifications for a surface-mount device (SMD) Light Emitting Diode (LED). The component is designed for automated printed circuit board (PCB) assembly processes, making it suitable for high-volume manufacturing. Its miniature size caters to space-constrained applications commonly found in modern portable and compact electronic devices.

1.1 Core Advantages and Target Market

The primary advantages of this LED include its compliance with RoHS (Restriction of Hazardous Substances) directives, compatibility with infrared (IR) reflow soldering processes, and packaging on industry-standard 8mm tape and 7-inch reels for automated pick-and-place equipment. It is designed to be integrated circuit (IC) compatible. The target applications span a broad range of consumer and industrial electronics, including but not limited to telecommunications equipment (e.g., cordless and cellular phones), office automation devices (e.g., notebook computers), network systems, home appliances, and indoor signage. Its primary functions are status indication, signal and symbol illumination, and front panel backlighting.

2. Package Dimensions and Pin Assignment

The LED features a specific SMD package. The lens color is yellow. The device contains two distinct LED chips within the same package: one emitting white light and the other emitting red light. The pin assignment is as follows: Pins 1 and 2 are assigned to the red LED, and pins 3 and 4 are assigned to the white LED. All dimensional tolerances are typically ±0.2 mm unless otherwise specified in the detailed mechanical drawings.

3. Technical Parameters: In-Depth Objective Interpretation

3.1 Absolute Maximum Ratings

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

• Power Dissipation: 102 mW for the white LED; 78 mW for the red LED. This is the maximum power the device can dissipate.
• Peak Forward Current: 100 mA for white, 80 mA for red. This is the maximum permissible pulsed current (1/10 duty cycle, 0.1ms pulse width).
• DC Forward Current: 30 mA for both colors. This is the maximum continuous forward current.
• Operating Temperature Range: -40°C to +85°C.
• Storage Temperature Range: -40°C to +100°C.

3.2 Electrical and Optical Characteristics

These are the typical performance parameters measured at Ta=25°C and a forward current (IF) of 20mA, unless stated otherwise.

• Luminous Intensity (Iv): White: 1500-3000 mcd (min-max). Red: 650-1300 mcd (min-max). Measured with a filter approximating the CIE photopic eye response.
• Viewing Angle (2θ½): Typically 120 degrees. This is the full angle at which luminous intensity drops to half of its axial value.
• Dominant Wavelength (λd): For the red LED: 617-626 nm (min-max). This parameter defines the perceived color.
• Peak Emission Wavelength (λP): For the red LED: typically 624 nm.
• Spectral Line Half-Width (Δλ): Typically 30 nm for white, 20 nm for red. This indicates the spectral purity.
• Forward Voltage (VF): White: 2.6-3.4 V. Red: 1.7-2.6 V. Tolerance is ±0.1V.
• Reverse Current (IR): Maximum 10 µA at a reverse voltage (VR) of 5V. The device is not designed for reverse bias operation.

4. Binning System Explanation

The LEDs are sorted into bins based on key performance parameters to ensure consistency in production runs.

4.1 Luminous Intensity (Iv) Rank

For the white LED, bins are defined as W1 (1500-2120 mcd) and W2 (2120-3000 mcd). For the red LED, bins are R1 (650-920 mcd) and R2 (920-1300 mcd). The tolerance within each intensity bin is ±11%.

4.2 CIE Chromaticity Rank

The white LED's color coordinates (x, y on the CIE 1931 chromaticity diagram) are binned into several categories (e.g., A1, A2, A3, B1, B2, B3), each defined by a quadrilateral area on the diagram. The tolerance for the chromaticity coordinates within each bin is ±0.01. This ensures color consistency for applications where precise white point matching is critical.

5. Performance Curve Analysis

The datasheet includes typical characteristic curves which are essential for circuit design. These curves graphically represent the relationship between various parameters, providing insight beyond the tabulated typical values. Designers should consult these curves to understand behavior under non-standard conditions (e.g., different forward currents or ambient temperatures). Key curves typically include the relationship between forward current and luminous intensity, forward current and forward voltage, and the effect of ambient temperature on luminous intensity. Analyzing these curves helps in selecting appropriate current-limiting resistors and predicting performance in the target operating environment.

6. Mechanical and Packaging Information

6.1 Recommended PCB Attachment Pad

A land pattern design is provided to ensure proper soldering and mechanical stability. Adhering to this recommended footprint is crucial for achieving reliable solder joints and managing heat dissipation during the reflow process.

6.2 Tape and Reel Packaging Dimensions

The components are supplied on 8mm wide embossed carrier tape wound onto 7-inch (178mm) diameter reels. Detailed dimensions for the tape pocket, reel hub, and overall reel are specified. Standard reel quantities are 2000 pieces per reel, with a minimum packing quantity of 500 pieces for remnants. The packaging conforms to EIA-481-1-B specifications.

7. Soldering and Assembly Guidelines

7.1 IR Reflow Soldering Profile

A suggested infrared (IR) reflow profile is provided for lead-free soldering processes, aligned with the J-STD-020B standard. Key parameters include a pre-heat temperature of 150-200°C, a maximum peak temperature of 260°C, and a time above liquidus not exceeding the specified limits. It is critical to note that the optimal profile depends on the specific PCB design, solder paste, and oven characteristics; therefore, board-level characterization is recommended.

7.2 Storage Conditions

For unopened, moisture-proof bags containing desiccant, LEDs should be stored at ≤ 30°C and ≤ 70% Relative Humidity (RH) and used within one year. Once the original packaging is opened, the storage environment should not exceed 30°C and 60% RH. Components exposed beyond 168 hours should be baked at approximately 60°C for at least 48 hours before soldering to prevent \"popcorning\" or delamination during reflow.

7.3 Cleaning

If cleaning is necessary after soldering, only specified alcohol-based solvents like ethyl alcohol or isopropyl alcohol should be used at normal temperature for less than one minute. Unspecified chemicals may damage the LED package.

8. Application Suggestions

8.1 Typical Application Scenarios

This dual-color LED is ideal for applications requiring multi-status indication from a single component footprint. Examples include power/charge status (red for charging, white for full), network activity indicators, or mode selection feedback in consumer electronics and industrial control panels.

8.2 Design Considerations

• Current Limiting: Always use a series resistor to limit the forward current to the recommended DC value (30mA max) or lower to ensure longevity and control brightness.
• Thermal Management: Ensure the PCB layout provides adequate thermal relief, especially if operating near maximum ratings, to prevent overheating and accelerated lumen depreciation.
• ESD Protection: While not explicitly stated, handling SMD LEDs with appropriate ESD precautions is standard industry practice.
• Optical Design: Consider the 120-degree viewing angle when designing light guides, lenses, or diffusers to achieve the desired illumination pattern.

9. Technical Comparison and Differentiation

Compared to single-color SMD LEDs, this dual-chip device offers space savings on the PCB by combining two indicator functions into one package. The separate white and red chips allow for independent control. The specified luminous intensity bins and CIE color bins provide a level of performance consistency important for applications requiring uniform appearance across multiple units. The compatibility with standard IR reflow processes differentiates it from LEDs that may require manual or wave soldering.

10. Frequently Asked Questions Based on Technical Parameters

Q: Can I drive the white and red LEDs simultaneously at their maximum DC current?
A: No. The Absolute Maximum Ratings for power dissipation (102mW white, 78mW red) and thermal considerations must be respected. Simultaneous operation at 30mA each would likely exceed the package's thermal capacity unless exceptional heat sinking is provided. Derating is advised.

Q: What is the difference between Dominant Wavelength and Peak Wavelength?
A: Peak Wavelength (λP) is the wavelength at the highest point in the LED's emission spectrum. Dominant Wavelength (λd) is derived from the color coordinates and represents the single wavelength of a monochromatic light that would match the perceived color of the LED. λd is more relevant for color specification.

Q: Why is the storage condition after opening the bag so strict (168 hours)?
A> SMD packages can absorb moisture from the atmosphere. During the high-temperature reflow soldering process, this trapped moisture can rapidly vaporize, creating internal pressure that may crack the package or delaminate internal bonds (\"popcorning\"). The 168-hour floor life and baking procedure mitigate this risk.

11. Practical Use Case

Scenario: Designing a Status Indicator for a Portable Device
A designer is creating a compact Bluetooth speaker. A single LTST-N682TWQEET LED is placed on the front panel. The microcontroller drives the red LED (pins 1-2) to indicate \"power on/charging\" and the white LED (pins 3-4) to indicate \"Bluetooth pairing mode/fully charged.\" Using a common current-limiting resistor value calculated for ~20mA (e.g., based on VF=3.0V for white and a 5V supply), both LEDs achieve good brightness. The 120-degree viewing angle ensures the status is visible from a wide range. The component is placed using automated assembly from the tape and reel.

12. Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light when an electric current passes through them. This phenomenon, called electroluminescence, occurs when electrons recombine with electron holes within the device, releasing energy in the form of photons. The color of the emitted light is determined by the energy band gap of the semiconductor material. The white LED in this package likely uses a blue or ultraviolet LED chip coated with a phosphor material that converts some of the emitted light to longer wavelengths, resulting in a broad spectrum perceived as white. The red LED uses an AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material, which is efficient for producing red, orange, and yellow light.

13. Development Trends

The general trend in SMD LEDs for indicator applications continues toward higher efficiency (more lumens per watt), allowing for the same brightness at lower currents, which reduces power consumption and thermal load. Package sizes are also miniaturizing further. There is a growing emphasis on tighter color and intensity binning to meet the demands of applications requiring high visual consistency, such as video walls and automotive interiors. Furthermore, integration of control electronics (e.g., constant current drivers) within the LED package is becoming more common for simplified design and improved performance stability.