LTW-Q35ZRGB RGB LED Datasheet - SMD Package - Red 2.1V / Green 2.9V / Blue 3.0V - 0.18W Total Power - English Technical Document

1. Product Overview

The LTW-Q35ZRGB is a compact, surface-mount RGB (Red, Green, Blue) LED designed for solid-state lighting applications. It combines three individual LED chips (red, green, blue) within a single package, enabling the generation of a wide spectrum of colors through additive color mixing. This device represents an energy-efficient alternative to conventional lighting, offering long operational life and high reliability.

1.1 Core Advantages

The primary advantages of this LED include its ultra-compact form factor, compatibility with automated pick-and-place assembly equipment, and suitability for standard infrared (IR) and vapor phase reflow soldering processes. It is designed as an EIA standard package and is compatible with integrated circuit (I.C.) drive levels. The product is compliant with green initiatives, being lead-free and adhering to RoHS directives.

1.2 Target Applications

This versatile LED is targeted at a broad range of lighting applications. Key markets include ambient lighting for household appliances, portable lighting solutions such as flashlights and bicycle lights, architectural lighting for both indoor and outdoor residential and commercial spaces (downlighters, cove lighting, undershelf lighting), decorative and entertainment lighting, security and garden lighting (bollards), and specialized signaling applications like traffic beacons, rail crossing lights, and edge-lit signs (e.g., exit signs, point-of-sale displays).

2. Technical Parameter Deep Dive

2.1 Electro-Optical Characteristics

All measurements are specified at an ambient temperature (Ta) of 25°C. The key parameters define the performance of each color channel (Red, Green, Blue) individually and the combined white light output.

• Luminous Flux (Φv): The typical luminous flux for individual colors at a forward current (IF) of 20mA is 2.55 lm (Red), 7.35 lm (Green), and 0.95 lm (Blue). When driven at specific currents to produce white light (R=25mA, G=13mA, B=15mA), the typical combined luminous flux is 10.50 lm.
• Luminous Intensity (Iv): The typical luminous intensity at IF=20mA is 920 mcd (Red), 2500 mcd (Green), and 340 mcd (Blue). The combined white light intensity under the specified drive conditions is 3500 mcd.
• Viewing Angle (θ1/2): The typical half-intensity viewing angle for the combined white output is 130 degrees, indicating a wide beam pattern.
• Dominant Wavelength (λd): Defines the perceived color of each chip. The specified ranges are 618-628 nm for Red, 520-530 nm for Green, and 465-475 nm for Blue.
• Forward Voltage (VF): The voltage drop across the LED at the test current. Typical values are 2.1V (Red at 20mA), 2.9V (Green at 20mA), and 3.0V (Blue at 20mA). Maximum values are 2.4V, 3.5V, and 3.5V respectively.
• ESD Withstand Voltage: The device can withstand Electrostatic Discharge (ESD) of 8KV using the Human Body Model (HBM), though proper ESD handling precautions are strongly recommended.

2.2 Absolute Maximum Ratings

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

• Power Dissipation (Po): Maximum allowable power for individual channels is 96 mW (Red), 144 mW (Green and Blue). The total power dissipation for the entire package must not exceed 180 mW.
• Forward Current: Continuous forward current (IF) for each channel is 40 mA. Peak forward current (IFP) for pulse operation (≤1/10 duty cycle, ≤10ms pulse width) is 100 mA per channel.
• Reverse Voltage (VR): Maximum of 5V. Operating under reverse bias can cause failure.
• Temperature Ranges: Operating temperature (Topr) is -40°C to +80°C. Storage temperature (Tstg) is -40°C to +100°C.
• Soldering Condition: The device can withstand lead-free soldering at 260°C for 5 seconds.

3. Binning System Explanation

The LED is sorted into bins based on luminous flux and chromaticity coordinates to ensure color and brightness consistency in production applications.

3.1 Luminous Flux Binning

White light output (when driven at R=25mA, G=13mA, B=15mA) is categorized into bins (V3 to V6). For example, bin V3 covers luminous flux from 8.00 lm (Min) to 10.50 lm (Max). Tolerance on each bin is +/-10%.

3.2 Color Chromaticity Binning

The combined white light chromaticity is defined on the CIE 1931 (x, y) diagram. The datasheet provides a detailed table of color ranks (A1 through D4), each specifying a quadrilateral area on the chromaticity chart defined by four (x, y) coordinate pairs. This allows designers to select LEDs with tightly controlled white point coordinates. The tolerance for each hue bin is +/- 0.01 in both x and y coordinates.

4. Performance Curve Analysis

The datasheet includes typical characteristic curves (not reproduced in the provided text but referenced). These curves are essential for design analysis.

• I-V (Current-Voltage) Curves: Show the relationship between forward current and forward voltage for each color chip across a range of currents and temperatures. This is critical for designing the correct current-limiting circuitry.
• Relative Luminous Intensity vs. Forward Current: Illustrates how light output scales with increasing drive current, highlighting potential non-linearities and efficiency roll-off at higher currents.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the thermal derating of light output. As junction temperature rises, luminous efficiency typically decreases.
• Spectral Power Distribution: Would show the relative intensity of light emitted at each wavelength for the red, green, and blue chips, defining the color gamut possible with this device.

5. Mechanical and Package Information

5.1 Outline Dimensions

The device has a specific form factor. All dimensions are in millimeters with a typical tolerance of ±0.2 mm. Key mechanical notes include the location of the injection point (which must be above the leads) and the fact that the heat slug is electrically conductive, which must be considered during PCB layout to prevent short circuits.

5.2 Polarity Identification and Pad Design

The datasheet provides a recommended printed circuit board (PCB) attachment pad layout. This includes the size, shape, and spacing of the solder pads for the four leads (anode and cathode for each color, likely with a common cathode or anode configuration) and the central thermal pad (heat slug). Correct pad design is crucial for reliable soldering, thermal management, and preventing tombstoning.

6. Soldering and Assembly Guide

6.1 Reflow Soldering Profile

A suggested infrared (IR) reflow soldering profile is provided, compliant with J-STD-020D for lead-free processes. This profile defines the preheat, soak, reflow (peak temperature), and cooling stages with specific time and temperature constraints to ensure reliable solder joints without damaging the LED package.

6.2 Cleaning and Handling

Cleaning should only be done with specified chemicals. The LED can be immersed in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute if necessary. Unspecified chemicals may damage the epoxy lens. Strict ESD precautions are mandated: use of wrist straps, anti-static gloves, and properly grounded equipment is recommended to prevent damage from electrostatic discharge.

7. Packaging and Ordering Information

The LEDs are supplied packaged in 12mm wide tape on 7-inch diameter reels, compatible with automated assembly equipment. The tape and reel packaging dimensions are specified to ensure compatibility with standard feeders. The part number is LTW-Q35ZRGB.

8. Application Suggestions

8.1 Design Considerations

• Current Driving: Use constant current drivers for each color channel to maintain stable color output and prevent thermal runaway. The forward voltage variations (see binning) make constant voltage driving impractical for color-critical applications.
• Thermal Management: Although compact, power dissipation (up to 180mW total) generates heat. Proper PCB thermal design, including the use of the thermal pad connected to a copper pour, is essential to maintain junction temperature within limits and ensure long-term reliability and stable light output.
• Color Mixing Control: To achieve specific white points or colors, pulse-width modulation (PWM) of each channel is the preferred method over analog dimming, as it maintains chromaticity over a wide dimming range.

9. Reliability and Testing

The datasheet outlines a comprehensive reliability test plan, demonstrating the product's robustness. Tests include Resistance to Soldering Heat (RTSH), Steady State Life Test (SSLT) at elevated temperature and current for 3000 hours, Temperature Cycling (TC), Thermal Shock (TS), and High Temperature/Humidity Storage (WHTS). Failure criteria are defined based on shifts in forward voltage (max 110% of upper spec limit), luminous flux (min 50% of lower spec limit), and chromaticity coordinates (shift <0.02).

10. Technical Comparison and Positioning

Compared to discrete single-color LEDs, this integrated RGB package saves significant board space and simplifies assembly. Its wide 130-degree viewing angle makes it suitable for area illumination rather than focused spot lighting. The specified ESD rating and compatibility with lead-free reflow meet modern manufacturing and reliability standards. The detailed binning structure allows it to compete in applications requiring color consistency, such as architectural lighting and signage.

11. Frequently Asked Questions (Based on Technical Parameters)

Q: How do I generate pure white light with this RGB LED?
A: Pure white is not a single point but a range on the chromaticity diagram. You must drive the Red, Green, and Blue channels at the specific currents listed in the luminous flux binning table (R=25mA, G=13mA, B=15mA) to achieve the white points defined in the color rank bins (A1-D4). The exact white point will depend on the specific bin of the LED.

Q: Can I drive the LED at its maximum continuous current (40mA per channel) continuously?
A: While possible, it is not recommended for optimal lifetime and efficiency. Driving at lower currents (e.g., the 20mA test condition or the mixed white condition) will result in lower junction temperature, higher efficacy (lumens per watt), and significantly longer operational life. Always consider the total power dissipation limit of 180mW.

Q: Why is the heat slug electrically conductive, and how do I handle this?
A: The slug is conductive to efficiently transfer heat from the LED die to the PCB. In your PCB layout, the pad for the slug must be electrically isolated from all other circuit traces unless it is intentionally connected to a specific potential (often ground). Creating a thermal relief connection to a large ground plane is a common practice.

12. Design and Usage Case Study

Scenario: Designing an edge-lit exit sign. Multiple LTW-Q35ZRGB LEDs would be placed along the edge of an acrylic light guide. A microcontroller would control the three channels of each LED. For constant illumination, the LEDs would be driven at the currents specified for white light. The wide viewing angle ensures even illumination across the sign face. The choice of a specific luminous flux bin (e.g., V3 or V4) ensures consistent brightness across all units. Selecting a tight color rank (e.g., all from bin B2) guarantees that all signs have an identical white color, which is crucial for brand and safety standard consistency. The SMD package allows for compact, low-profile sign design and automated assembly.

13. Operating Principle

The LED operates on the principle of electroluminescence in semiconductor materials. When a forward voltage exceeding the diode's threshold is applied, electrons recombine with holes within the active region of the semiconductor chip (composed of materials like AlInGaP for red and InGaN for green/blue), releasing energy in the form of photons (light). The specific bandgap of the semiconductor material determines the wavelength (color) of the emitted light. The RGB package integrates three such chips, and their light mixes additively within the epoxy lens to produce the perceived output color.

14. Technology Trends

The device reflects ongoing trends in solid-state lighting: increased integration (multiple chips in one package), improved efficiency (higher lumens per watt), miniaturization, and enhanced reliability for harsh environments. The detailed binning system addresses the market's demand for color consistency in professional lighting applications. Future evolution may include higher power density, integrated drivers or control circuitry within the package, and even broader color gamuts for display applications.