渦巻いた1000-1750NM LED
導入
In the application and design of high-power LEDs (such as the 3535 パッケージ), thermal management and electrical design are the core elements determining LED lifespan and reliability. Depending on the material and wavelength of the LED chip, the electrical characteristics of the thermal pad differ fundamentally. This article provides an in-depth analysis of the key differences in thermal pad design between Red/Yellow (AlInGaP) and Blue/White (InGaN) LED.
1. Core Principle: Thermally Isolated Design
The 3535 LED utilizes a thermally isolated design, with the core objectives of:
- Efficient Dissipation: Reducing the chip’s junction temperature.
- Stability & 信頼性: Minimizing chip light decay caused by overheating.
- Extended Lifespan: Ensuring the LED’s life cycle under long-term high-power operation.
Regardless of the LED type, の heat flow path remains identical:
LED Chip → Thermal Pad → PCB Copper → Thermal Vias → PCB Backside Heat Dissipation
2. Red/Yellow LED (AlInGaP Chip Structure)
- Connection Feature: Thermal pad connected to the anode (Thermal Pad = Anode +).
- Electrical & Thermal Conduction: For Red/Yellow LEDs, the thermal pad serves as both a heat dissipation channel and a current path. Current conducts through the thermal pad.
- PCB Design Caution: When designing the substrate, it is critical to note that the thermal pad of Red/Yellow LEDs carries a positive charge (+). It must not directly share uninsulated copper foil with other unrelated conductive circuits or ground (GND), otherwise, a short circuit will occur.
3. Blue/White LED (InGaN Chip Structure)
- Connection Feature: Thermal pad isolated electrically (Thermal Pad = Thermal Only).
- Heat Dissipation Only: The thermal pad of Blue/White LEDs is used exclusively for heat dissipation and has no electrical connection attributes (no current flows through it).
- PCB Design Caution: Since its thermal pad is electrically isolated, it offers higher flexibility during PCB layout. The thermal pad can be directly connected to a large area of ground (GND) copper foil to achieve optimal thermal dissipation without worrying about electrical interference.
Key Points Summary
- Power Conversion Characteristic: Over 70% of electrical energy in high-power LEDs is converted to heat. High luminous efficiency relies heavily on high-reliability thermal design.
- Red/Yellow vs. Blue/White: Red/Yellow thermal pads are electrically active (Anode+), while Blue/White thermal pads are electrically isolated.
- Design Benefits: Efficient thermal design effectively reduces junction temperature, thereby significantly improving luminous efficiency and overall system reliability.
