Ceramic 3535 Series 1W Infrared LED Datasheet - Dimensions 3.5x3.5x0.9mm - Voltage 1.5V - Power 1W - Infrared 850nm

1. Product Overview

The Ceramic 3535 series is a high-power, surface-mount LED designed for applications requiring robust and reliable infrared illumination. This 1W device utilizes a ceramic substrate, offering superior thermal management and long-term stability compared to traditional plastic packages. The primary emission wavelength is 850nm, making it suitable for a wide range of sensing, machine vision, and security applications.

The core advantages of this series include its excellent heat dissipation capability due to the ceramic construction, a wide 120-degree viewing angle for broad coverage, and a compact 3.5mm x 3.5mm footprint that facilitates high-density PCB layouts. The target markets are industrial automation, surveillance systems, biometric sensors, and any application demanding consistent, high-intensity infrared light.

2. Technical Parameters and Objective Interpretation

2.1 Absolute Maximum Ratings

The following parameters define the limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed.

• Forward Current (IF): 500 mA (DC)
• Forward Pulse Current (IFP): 700 mA (Pulse width ≤10ms, Duty cycle ≤1/10)
• Power Dissipation (PD): 1000 mW
• Operating Temperature (Topr): -40°C to +100°C
• Storage Temperature (Tstg): -40°C to +100°C
• Junction Temperature (Tj): 125°C
• Soldering Temperature (Tsld): Reflow soldering at 230°C or 260°C for a maximum of 10 seconds.

2.2 Electro-Optical Characteristics (Typical @ Ta=25°C)

These parameters represent the typical performance under specified test conditions.

• Forward Voltage (VF): 1.5 V (Typical), 2.0 V (Maximum) at IF=350mA. The low forward voltage contributes to higher system efficiency.
• Reverse Voltage (VR): 5 V. Exceeding this voltage in reverse bias can cause immediate failure.
• Peak Wavelength (λd): 850 nm. This is the wavelength at which the radiant intensity is highest.
• Reverse Current (IR): 50 μA (Maximum) at VR=5V.
• Viewing Angle (2θ1/2): 120 degrees. This wide angle provides a broad, uniform illumination pattern.

2.3 Thermal Characteristics

The ceramic package is the key thermal feature. Ceramic materials have high thermal conductivity, which efficiently transfers heat from the LED chip's junction to the PCB and ambient environment. This directly impacts the device's lifetime and luminous maintenance. Proper thermal design on the application PCB, including adequate copper area and potential heatsinking, is critical to maintain the junction temperature below the maximum 125°C rating, especially when operating at the full 350mA drive current.

3. Binning System Explanation

The product is classified into bins to ensure consistency within a production batch. Designers should specify bins to guarantee performance matching in their applications.

3.1 Forward Voltage Binning

LEDs are sorted based on their forward voltage (VF) at the test current.

• Code A: VF = 1.4V to 1.6V
• Code B: VF = 1.6V to 1.8V
• Code C: VF = 1.8V to 2.0V

Note: Measurement tolerance is ±0.08V. Selecting a tight voltage bin can simplify current regulation circuit design.

3.2 Peak Wavelength Binning

For this specific model (T1901PIA), the wavelength is binned as follows:

• Code I2: λd = 845nm to 865nm. This tight 20nm range is suitable for applications sensitive to specific infrared wavelengths, such as certain types of night vision or optical sensors.

4. Performance Curve Analysis

The datasheet provides graphical data essential for circuit and thermal design.

4.1 Forward Current vs. Forward Voltage (I-V Curve)

This curve shows the exponential relationship between current and voltage. The typical VF of 1.5V at 350mA is a key point. Designers use this curve to select appropriate current-limiting resistors or to design constant-current drivers. The curve will shift with temperature; voltage decreases as junction temperature increases for a given current.

4.2 Relative Radiant Power vs. Junction Temperature

This graph illustrates the thermal derating of the LED's output. Infrared LEDs generally exhibit less efficiency drop with temperature compared to visible LEDs, but output still decreases as the junction temperature rises. This must be accounted for in thermal management to ensure consistent performance over the product's lifetime and across operating temperatures.

4.3 Spectral Distribution Curve

The curve confirms the dominant 850nm peak wavelength and shows the spectral bandwidth. The narrow bandwidth is typical for high-quality infrared emitters. Understanding the spectrum is vital for pairing with matching photodetectors or camera sensors that have specific spectral responsivity.

5. Mechanical and Package Information

5.1 Package Dimensions and Outline Drawing

The device has a square ceramic body measuring 3.5mm x 3.5mm. The overall height is approximately 0.9mm. Detailed dimensional drawings with tolerances (e.g., ±0.10mm for .X dimensions, ±0.05mm for .XX dimensions) are provided for precise PCB layout.

5.2 Recommended Pad Layout and Stencil Design

A land pattern design is suggested to ensure reliable soldering and optimal thermal transfer. The pad layout typically includes two anode/cathode pads and a central thermal pad. The stencil design (solder paste mask) is also specified, often recommending a reduced aperture for the large thermal pad to prevent solder bridging and excessive paste volume. Following these recommendations is crucial for achieving a reliable solder joint and maximizing heat dissipation from the thermal pad into the PCB.

5.3 Polarity Identification

The cathode is typically marked on the top of the package, often with a green tint or a notch/cut corner on the lens. The PCB footprint should include a polarity marker matching this feature to prevent incorrect placement.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Parameters

The LED is compatible with standard infrared or convection reflow processes. The maximum peak temperature is 260°C, with a time above liquidus (e.g., 217°C) not exceeding 10 seconds. A recommended reflow profile should be followed to avoid thermal shock. The ceramic package is generally more resistant to moisture absorption than plastic packages, but standard handling precautions for moisture-sensitive devices (MSD) may still apply depending on the specific materials used.

6.2 Handling and Storage Precautions

Store LEDs in a dry, anti-static environment. Avoid mechanical stress on the lens. Use ESD precautions during handling. Do not clean with ultrasonic cleaners after soldering, as this may damage the internal structure.

7. Packaging and Ordering Information

7.1 Tape and Reel Packaging

The product is supplied on embossed carrier tape wound on reels, suitable for automated pick-and-place assembly machines. The tape dimensions (pocket size, pitch) are standardized. Reel quantities are typically several thousand pieces per reel.

7.2 Model Numbering System

The part number (e.g., T1901PIA) encodes key attributes:

• T: Series identifier.
• 19: Package code for Ceramic 3535.
• P: Die count code for a single high-power die.
• I: Color code for Infrared (IR).
• A: Internal code or bin code.
• Additional suffixes may indicate voltage bin, wavelength bin, etc.

Other codes defined in the system include color (R, G, B, Y, W, etc.), die count (S, P, 2, 3), and lens type (00 for none, 01 for lens).

8. Application Suggestions

8.1 Typical Application Scenarios

• Surveillance & Security: Illumination for CCTV cameras with IR-cut filters, providing invisible night vision.
• Machine Vision: Structured light, contrast enhancement, or defect detection in automated inspection systems.
• Biometric Sensors: Iris recognition, facial recognition, or fingerprint scanners.
• Proximity & Gesture Sensing: Used in consumer electronics and automotive applications.
• Optical Switches & Encoders: Providing the light source for interruption-based sensing.

8.2 Design Considerations

• Driver Circuit: Use a constant current driver for stable output. The low VF allows for operation from low-voltage supplies. Consider using a switching regulator for high-efficiency operation at full power.
• Thermal Management: This is paramount. Connect the thermal pad to a large copper pour on the PCB with multiple thermal vias to inner layers or a bottom-side heatsink. Thermal simulation is recommended for high-power or high-ambient-temperature applications.
• Optical Design: The 120-degree beam may require secondary optics (lenses, diffusers) to shape the light for specific applications. The ceramic package surface may not be ideal for direct optical coupling; a primary lens is often incorporated.

9. Technical Comparison and Differentiation

Compared to standard plastic 3535 LEDs, this ceramic version offers significant advantages:

• Superior Thermal Performance: Lower thermal resistance from junction to board, leading to lower operating junction temperature, higher maximum drive current potential, and significantly longer lifetime at high power.
• Enhanced Reliability: Ceramic is inert and does not degrade or yellow under high-temperature or high-UV exposure, unlike some plastics. It is also more resistant to mechanical cracking.
• Stable Optical Output: Better thermal management results in more stable wavelength and radiant power over time and temperature cycles.
• The trade-off is typically a slightly higher unit cost compared to plastic packages.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 What is the difference between forward current (IF) and pulse current (IFP)?

IF (500mA) is the maximum continuous DC current the LED can handle. IFP (700mA) is the maximum current allowed in short pulses (≤10ms width, ≤10% duty cycle). Pulsing allows for higher instantaneous radiant output, useful in strobe or pulsed-sensing applications, but average power must not exceed the 1W limit.

10.2 How do I select the correct voltage bin?

If your design uses a simple series resistor for current limiting, a tighter VF bin (e.g., all Code B) ensures more consistent current and therefore consistent brightness across all LEDs in an array. For designs using active constant-current drivers, the voltage bin is less critical, as the driver will adjust the voltage to maintain the set current.

10.3 Can I drive this LED without a heatsink?

At the full 350mA/1W rating, a proper thermal path is mandatory. The ceramic package helps, but it must be connected to the PCB's thermal management system. For lower drive currents (e.g., 100-200mA) or pulsed operation, the requirements are less stringent, but thermal analysis is still recommended.

11. Practical Application Case Study

Scenario: High-Speed Industrial Barcode Scanner. A scanner needs to read codes on fast-moving packages. The system uses a pulsed 850nm infrared LED array to illuminate the target. The Ceramic 3535 LED is chosen for its ability to handle high pulse currents (up to 700mA) for bright, short-duration flashes, capturing clear images without motion blur. The ceramic package's thermal stability ensures consistent pulse amplitude and wavelength over long operating periods in a warm factory environment. The wide 120-degree beam allows fewer LEDs to cover the scanning field. The PCB is designed with thick copper layers and thermal vias under each LED's thermal pad to dissipate the average heat generated during the pulsed operation.

12. Operating Principle Introduction

An Infrared Light Emitting Diode (IR LED) operates on the same electroluminescence principle as a visible LED. 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. The wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material used. For 850nm emission, materials like Aluminum Gallium Arsenide (AlGaAs) are commonly used. The ceramic package serves primarily as a mechanically robust and thermally conductive housing for the semiconductor die, wire bonds, and primary optic (if present).

13. Technology Trends and Developments

The trend in high-power infrared LEDs is towards higher wall-plug efficiency (more light output per electrical watt input) and increased power density. This drives the adoption of advanced chip technologies (flip-chip, thin-film) and packaging materials like ceramics and metal-core substrates for optimal thermal management. There is also a focus on improving reliability and lifetime under harsh conditions (high temperature, high humidity). Furthermore, the integration of drivers and sensors with the LED into smart modules is a growing trend, simplifying system design for end-users. The demand for specific, narrow wavelength bands for sensing applications continues to push advancements in epitaxial material growth and device engineering.