LTLMH4T BR7DA LED Lamp Datasheet - Dimensions 4.2x4.2x6.2mm - Voltage 2.9V - Power 85mW - Blue 470nm - English Technical Document

1. Product Overview

The LTLMH4T BR7DA is a high-brightness surface mount LED lamp designed for demanding lighting applications. This device utilizes advanced InGaN (Indium Gallium Nitride) semiconductor technology to produce blue light with a dominant wavelength of 470nm. Encapsulated in a diffused blue epoxy package, it is engineered for superior performance in sign board applications, offering a controlled radiation pattern without the need for additional secondary optics. Its surface-mount device (SMD) form factor ensures compatibility with standard, high-volume SMT (Surface Mount Technology) assembly lines and industrial reflow soldering processes.

The core advantages of this LED include its high luminous intensity output, which can reach up to 2850 millicandelas (mcd), coupled with low power consumption for high efficiency. The package is constructed using advanced epoxy materials that provide excellent moisture resistance and UV protection, enhancing its reliability for both indoor and outdoor use. Furthermore, the product is compliant with environmental standards, being lead-free, halogen-free, and RoHS compliant.

The target market for this component is primarily the professional signage industry. Its typical applications include video message signs, traffic signs, and various forms of message displays where consistent, bright, and reliable illumination is critical. The LED's design is particularly suitable for applications requiring a smooth radiation pattern and controlled viewing angles.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The absolute maximum ratings define the limits beyond which permanent damage to the LED may occur. These ratings are specified at an ambient temperature (TA) of 25°C. The maximum power dissipation is 85 mW. The device can handle a peak forward current of 100 mA, but only under pulsed conditions with a duty cycle of 10% or less and a pulse width not exceeding 10 milliseconds. The continuous DC forward current rating is a more conservative 25 mA. To ensure safe operation at higher temperatures, a derating factor of 0.62 mA per degree Celsius applies linearly from 45°C upwards. The operational temperature range is from -40°C to +85°C, while the storage temperature range extends to +100°C. Critically for assembly, the LED can withstand a reflow soldering profile with a peak temperature of 260°C for a maximum of 10 seconds.

2.2 Electrical and Optical Characteristics

The electrical and optical characteristics are the key performance parameters under normal operating conditions, also specified at TA=25°C.

• Luminous Intensity (Iv): Measured at a forward current (IF) of 20mA, the luminous intensity has a typical value of 1600 mcd, with a minimum of 1000 mcd and a maximum of 2850 mcd. The Iv classification is marked on the packing bag, and guarantee tests include a ±15% tolerance.
• Viewing Angle (2θ1/2): The device features a typical viewing angle of 70/45 degrees. This parameter, defined as the off-axis angle where luminous intensity drops to half its axial value, indicates a moderately focused beam pattern suitable for directed lighting.
• Wavelength: The peak emission wavelength (λP) is typically 461 nm. The dominant wavelength (λd), which defines the perceived color, ranges from 465 nm to 475 nm, with a typical value of 470 nm (blue). The spectral line half-width (Δλ) is typically 23 nm.
• Forward Voltage (VF): At IF=20mA, the forward voltage typically drops 2.9V, with a range from 2.5V to 3.5V. This parameter is crucial for driver circuit design.
• Reverse Current (IR): The maximum reverse current is 10 μA when a reverse voltage (VR) of 5V is applied. It is important to note that this device is not designed for reverse-bias operation; this test condition is for characterization only.

3. Binning System Specification

To ensure color and brightness consistency in production applications, the LEDs are sorted into bins based on key parameters.

3.1 Luminous Intensity Binning

LEDs are classified into four intensity bins (BQ, BR, BS, BT) based on their measured luminous intensity at 20mA. The bin limits are: BQ (1000-1300 mcd), BR (1300-1700 mcd), BS (1700-2200 mcd), and BT (2200-2850 mcd). A tolerance of ±15% applies to each bin limit.

3.2 Dominant Wavelength Binning

For color consistency, dominant wavelength is binned into two codes: B1 (465-470 nm) and B2 (470-475 nm). The tolerance for each bin limit is ±1 nm. The part number LTLMH4T BR7DA indicates a specific combination of these bins (e.g., 'BR' for intensity and '7D' likely relating to the wavelength bin, though the exact code mapping in the part number is not fully detailed in the provided extract).

4. Performance Curve Analysis

While the specific graphical curves are not detailed in the text extract, typical performance curves for such LEDs would include:

• IV Curve (Current vs. Voltage): This curve shows the exponential relationship between forward voltage and forward current. It is essential for determining the operating point and thermal effects on voltage drop.
• Luminous Intensity vs. Forward Current: This graph typically shows a near-linear relationship between drive current and light output within the recommended operating range, highlighting the efficiency of the device.
• Luminous Intensity vs. Ambient Temperature: This curve demonstrates the thermal quenching effect, where light output decreases as the junction temperature rises. Understanding this is vital for thermal management in the final application.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at ~461nm and the spectral width, which affects color purity.

Designers should consult these curves to optimize drive conditions and heat sinking for consistent performance over the product's lifetime.

5. Mechanical and Package Information

5.1 Outline Dimensions

The LED has a compact, rectangular surface-mount package. Key dimensions include a body size of approximately 4.2mm (±0.2mm) in length and width. The total height, including the lens, is 6.2mm (±0.5mm). The package features a flange for mechanical stability during placement. Tolerance for most dimensions is ±0.25mm unless otherwise specified.

5.2 Pad Design and Polarity Identification

The device has three electrical terminals (P1, P2, P3). P1 and P3 are the anode (+) connections, while P2 is the cathode (-) connection. This configuration may be used for improved current distribution or thermal management. The recommended solder pad pattern on the PCB includes a larger pad (often connected to P3) which is specifically designed to be connected to a heat sink or cooling mechanism to effectively distribute heat generated during operation. A fillet radius (R0.5) is suggested on the pad design to ensure reliable solder joint formation.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

The LED is rated Moisture Sensitive Level 3 (MSL3) per JEDEC J-STD-020. The recommended lead-free reflow profile parameters are: Preheat/Soak from 150°C to 200°C for a maximum of 120 seconds. The time above liquidous temperature (217°C) should be between 60 and 150 seconds. The peak package body temperature (Tp) must not exceed 260°C, and the time within 5°C of the specified classification temperature (255°C) should be a maximum of 30 seconds. The total time from 25°C to peak temperature should not exceed 5 minutes. Reflow soldering must not be performed more than twice.

6.2 Storage and Handling

LEDs in sealed moisture barrier bags can be stored for up to 12 months at <30°C and 90% RH. After opening the bag, components must be kept under <30°C and 60% RH and must be soldered within 168 hours (7 days). Baking at 60°C±5°C for 20 hours is required if the humidity indicator card shows >10% RH, if floor life exceeds 168 hours, or if components are exposed to >30°C and 60% RH. Baking should be performed only once.

6.3 Cleaning and Manual Soldering

If cleaning is necessary, only alcohol-based solvents like isopropyl alcohol should be used. If hand soldering is required, it must be limited to one time only with an iron temperature not exceeding 315°C for a maximum of 3 seconds per joint. External stress must not be applied to the LED during soldering while it is at high temperature, and rapid cooling from peak temperature should be avoided.

7. Packaging and Ordering Information

7.1 Packaging Specification

The LEDs are supplied on embossed carrier tape and reel. The tape dimensions are specified, with a pocket pitch of 8.0mm (±0.1mm) and a tape width of 16.0mm (±0.3mm). Each reel contains 1,000 pieces, packaged within a moisture barrier bag marked with an electrostatic discharge (ESD) warning. Three reels are packed per inner carton (total 3,000 pcs), and nine inner cartons are packed per outer carton (total 27,000 pcs). In every shipping lot, only the last pack may be non-full.

8. Application Recommendations

8.1 Typical Application Scenarios

This LED is well-suited for indoor and outdoor signage, including video message signs, traffic signs, and general message displays. Its high brightness and controlled viewing angle make it ideal for applications where the light needs to be directed towards the viewer for maximum visibility, even in ambient light conditions.

8.2 Design Considerations

• Current Driving: Use a constant current driver set to 20mA for typical operation, ensuring it stays within the absolute maximum of 25mA DC. Consider derating at high ambient temperatures.
• Thermal Management: Connect the designated thermal pad (P3) to a copper pour or dedicated heat sink on the PCB to effectively transfer heat away from the LED junction, maintaining light output and longevity.
• Optical Design: The built-in diffused lens provides a smooth radiation pattern. For specific beam shapes, secondary optics can be added, though the native 70/45-degree angle is often sufficient for sign applications.
• ESD Protection: Implement standard ESD precautions during handling and assembly, as indicated on the packaging.

9. Technical Comparison and Differentiation

Compared to standard SMD LEDs (like 3528 or 5050 packages) or PLCC (Plastic Leaded Chip Carrier) LEDs, this surface mount lamp offers distinct advantages for signage. Its primary differentiator is the integrated lens design that provides a smooth radiation pattern and controlled, narrow viewing angles without requiring an additional external optical lens. This simplifies the mechanical design of the sign, reduces component count, and can lower overall assembly cost. The high luminous intensity in a compact package also allows for brighter displays or the use of fewer LEDs per sign area. The robust epoxy package with enhanced moisture and UV resistance provides better reliability for outdoor applications compared to some standard SMD packages.

10. Frequently Asked Questions (FAQ)

Q1: What is the meaning of the part number LTLMH4T BR7DA?
A1: The part number encodes specific product characteristics. 'LTLMH4T' likely refers to the product family and package type. 'BR' indicates the luminous intensity bin (1300-1700 mcd). '7D' is assumed to correlate with the dominant wavelength bin (likely 470-475nm, B2). Always confirm the exact binning from the supplier's full datasheet or packing label.

Q2: Can I drive this LED with a constant voltage source?
A2: It is not recommended. LEDs are current-driven devices. Their forward voltage has a tolerance (2.5V-3.5V). A constant voltage source could lead to excessive current variation between units, causing differences in brightness and potentially shortening lifespan. Always use a constant current driver or a circuit that actively limits current.

Q3: Why is there a thermal pad (P3), and do I have to connect it?
A3: The thermal pad is designed to transfer heat from the LED die to the PCB. Connecting it to a copper area or heat sink is strongly recommended, especially when operating at high ambient temperatures or at full drive current. Proper thermal management ensures stable light output and maximizes the operational lifetime of the LED.

Q4: The datasheet says MSL3. What happens if I exceed the 168-hour floor life?
A4: Exceeding the floor life exposes the LED to ambient moisture, which can vaporize during reflow soldering, causing internal package damage (\"popcorning\"). If the floor life is exceeded, you must bake the components at 60°C for 20 hours before soldering, as per the instructions in section 8.2.

11. Practical Design and Usage Case

Case: Designing a High-Visibility Outdoor Traffic Sign
A designer is creating a solar-powered, variable message traffic sign. They select the LTLMH4T BR7DA LED for its high brightness (BR bin, ~1500 mcd typ.) and blue color (470nm). The sign must be readable in direct sunlight. The designer calculates that an array of 100 LEDs, driven at 18mA (slightly below typical to enhance longevity and account for solar input variance), will provide sufficient luminous intensity. A constant current driver IC is selected to power the array in series-parallel configuration. The PCB is designed with large copper fills connected to the P3 pads of each LED, which are in turn connected to the aluminum backplate of the sign housing acting as a heat sink. The MSL3 handling procedure is strictly followed during assembly to prevent moisture-related failures. This design results in a reliable, bright, and energy-efficient sign suitable for 24/7 outdoor operation.

12. Technology Principle Introduction

This LED is based on InGaN (Indium Gallium Nitride) semiconductor technology. When a forward voltage is applied across the p-n junction, electrons and holes recombine in the active region, 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 470nm. The epoxy encapsulant serves multiple purposes: it protects the delicate semiconductor die, acts as a primary lens to shape the light output, and contains diffusing particles to create a uniform appearance. The package also includes a reflective cup to direct light upward and leads designed for both electrical connection and thermal dissipation.

13. Industry Trends and Development

The surface mount LED market continues to evolve towards higher efficiency (more lumens per watt), increased power density, and improved color consistency and rendering. Trends relevant to this type of component include the push for even narrower binning tolerances to ensure uniformity in large displays, the development of epoxy and silicone materials with greater resistance to harsh environmental conditions (heat, humidity, UV), and the integration of more sophisticated internal optics for precise beam control. Furthermore, there is a growing emphasis on sustainability, driving advancements in materials and manufacturing processes to further reduce environmental impact. The underlying InGaN technology is also being refined to push the limits of efficiency and to enable new wavelength ranges for specialized applications.