SMD LED LTST-E682QETBWT Datasheet - Red & Blue - 30mA - 75mW/108mW - English Technical Document

1. Product Overview

The LTST-E682QETBWT is a surface-mount device (SMD) light-emitting diode (LED) featuring a dual-color configuration within a single package. It is designed for automated printed circuit board (PCB) assembly processes, making it suitable for high-volume manufacturing. The component combines two distinct semiconductor materials: AlInGaP for red light emission and InGaN for blue light emission, each controlled via separate anode-cathode pairs. This design is targeted at applications requiring compact, reliable status indication or backlighting in space-constrained electronic devices.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Packaged in 8mm tape on 7-inch diameter reels for automated pick-and-place equipment compatibility.
• Standard EIA (Electronic Industries Alliance) package outline.
• Integrated circuit (IC) compatible drive levels.
• Suitable for infrared (IR) reflow soldering processes.
• Preconditioned to JEDEC (Joint Electron Device Engineering Council) moisture sensitivity level 3.

1.2 Applications

This LED is intended for a broad range of consumer and industrial electronics where reliable visual indicators are needed. Typical use cases include status and power indicators in telecommunications equipment (e.g., routers, modems), office automation devices (e.g., printers, scanners), home appliances, and various industrial control panels. It can also be used for front panel backlighting of buttons or symbols, and in low-resolution indoor signage where specific color cues are required.

2. Technical Specifications Deep Dive

This section provides a detailed analysis of the electrical, optical, and thermal parameters that define the operational boundaries and performance of the LED.

2.1 Absolute Maximum Ratings

These values represent the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed. All ratings are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): Red: 75 mW, Blue: 108 mW. This is the maximum allowable power loss as heat. Exceeding this can lead to junction temperature rise and accelerated degradation.
• Peak Forward Current (I_FP): 100 mA for both colors. This is permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to prevent overheating.
• DC Forward Current (I_F): 30 mA for both colors. This is the maximum continuous current recommended for reliable long-term operation.
• Operating Temperature Range: -40°C to +85°C. The device is designed to function within this ambient temperature span.
• Storage Temperature Range: -40°C to +100°C. The device can be stored without applied power within these limits.

2.2 Electro-Optical Characteristics

These parameters are measured at Ta=25°C with a forward current (I_F) of 20mA, which is the standard test condition.

• Luminous Intensity (I_V): A key measure of perceived light output. For the Red LED, the typical range is 450-1080 millicandelas (mcd). For the Blue LED, the range is 280-680 mcd. The actual value for a specific unit depends on its bin rank.
• Viewing Angle (2θ_1/2): Typically 120 degrees. This is the full angle at which the luminous intensity drops to half of its peak axial value. The diffused lens creates a wide, Lambertian-like emission pattern suitable for wide-angle viewing.
• Peak Emission Wavelength (λ_P): Red: 632 nm (typical), Blue: 468 nm (typical). This is the wavelength at which the spectral power distribution is maximum.
• Dominant Wavelength (λ_d): Red: 616-628 nm, Blue: 465-475 nm. This is the single wavelength perceived by the human eye that best matches the LED's color. It is derived from the CIE chromaticity coordinates.
• Spectral Line Half-Width (Δλ): Red: 20 nm, Blue: 25 nm (typical). This indicates the spectral purity; a smaller value means a more monochromatic color.
• Forward Voltage (V_F): Red: 1.7-2.5V, Blue: 2.6-3.6V at 20mA. The Blue LED requires a higher voltage due to the wider bandgap of InGaN material. Designers must account for this difference when driving the two colors from the same voltage rail.
• Reverse Current (I_R): Maximum 10 µA at a reverse voltage (V_R) of 5V. LEDs are not designed for reverse bias operation; this parameter is primarily for quality testing.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins. The LTST-E682QETBWT uses a luminous intensity binning system.

3.1 Luminous Intensity Bins

Each color has three intensity bins with a tolerance of ±11% within each bin.

• Red (AlInGaP) Bins:
  • R1: 450 - 600 mcd
  • R2: 600 - 805 mcd
  • R3: 805 - 1080 mcd
• Blue (InGaN) Bins:
  • B1: 280 - 375 mcd
  • B2: 375 - 500 mcd
  • B3: 500 - 680 mcd

This binning allows designers to select parts that meet specific brightness requirements for their application, ensuring visual consistency across multiple units in a product.

4. Mechanical and Package Information

4.1 Package Dimensions and Pinout

The device conforms to a standard SMD footprint. Critical dimensions include body size and lead spacing, which are essential for PCB land pattern design. The pin assignment is as follows: Pins 1 and 2 are for the Blue LED, and Pins 3 and 4 are for the Red LED. The cathode and anode for each color are internally connected to specific pins; consulting the detailed package drawing is necessary for correct orientation. All dimensional tolerances are typically ±0.2mm unless otherwise specified.

4.2 Recommended PCB Attachment Pad

A suggested land pattern (copper pad layout) is provided for infrared or vapor phase reflow soldering. Adhering to this recommendation helps achieve reliable solder fillets, proper alignment, and effective heat transfer during the soldering process, minimizing tombstoning or misalignment defects.

5. Assembly and Handling Guidelines

5.1 Soldering Process

The component is compatible with lead-free (Pb-free) infrared reflow soldering processes. A suggested temperature profile compliant with J-STD-020B is provided. Key parameters include:

• Preheat: 150-200°C for up to 120 seconds to gradually heat the board and activate flux.
• Peak Temperature: Maximum 260°C. The time above 217°C (liquidus temperature for SnAgCu solder) should be controlled.
• Total Soldering Time: Maximum 10 seconds at peak temperature, with a maximum of two reflow cycles allowed.

For manual rework with a soldering iron, the tip temperature should not exceed 300°C, and contact time should be limited to 3 seconds per joint, for one time only, to prevent thermal damage to the plastic package and the semiconductor die.

5.2 Cleaning

If post-solder cleaning is required, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute is acceptable. Harsh or unspecified chemicals can damage the epoxy lens and package, leading to discoloration or cracking.

5.3 Moisture Sensitivity and Storage

Packaged as Moisture Sensitivity Level 3 (MSL3), the LEDs are sealed in a moisture-barrier bag with desiccant. They should be stored at ≤30°C and ≤70% relative humidity (RH). Once the original bag is opened, the \"floor life\" is 168 hours (7 days) under conditions of ≤30°C/60% RH before they must be soldered. If this window is exceeded, a bake-out at approximately 60°C for at least 48 hours is required to remove absorbed moisture and prevent \"popcorning\" (package cracking) during reflow.

6. Application Notes and Design Considerations

6.1 Drive Method

LEDs are current-driven devices. To ensure uniform brightness, especially when connecting multiple LEDs in parallel, each LED or each color channel should be driven with a constant current source or through a current-limiting resistor. The forward voltage (V_F) has a tolerance and varies with temperature; driving with a constant voltage source without a series resistor can lead to excessive current and rapid failure.

6.2 Thermal Management

While the power dissipation is relatively low, proper thermal design extends lifetime and maintains stable light output. The PCB itself acts as a heat sink. Ensuring adequate copper area connected to the thermal pads (if any) or the LED's leads helps dissipate heat. Operating at or near the maximum DC current in high ambient temperatures will increase the junction temperature, which can reduce luminous output and accelerate long-term lumen depreciation.

6.3 Optical Design

The 120-degree viewing angle and diffused lens provide a wide, soft light emission suitable for panel indicators where viewing is not strictly axial. For applications requiring more directed light, secondary optics (e.g., light pipes, lenses) may be necessary. The different luminous intensities of the red and blue chips may require independent current adjustment if color balance in a mixed-light scenario is critical.

7. Reliability and Operational Limits

The device is intended for general-purpose electronics. Applications involving extreme reliability requirements, such as in aviation, transportation, medical life-support, or safety-critical systems, require prior consultation and qualification. The operational limits defined in the Absolute Maximum Ratings and the assembly guidelines must be strictly observed to ensure the specified performance and longevity. Failure to do so, such as applying reverse bias, exceeding current limits, or improper soldering, will void reliability expectations.