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High-performance light-emitting diodes encapsulated with silica-filled epoxy materials
Tian Li1, Jie Zhang, Huiping Wang
1State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University , Shanghai 200433, China.
ACS Applied Materials & Interfaces
|August 28, 2013
Summary
High-performance light-emitting diodes (LEDs) were achieved by incorporating inorganic silica fillers into epoxy packaging. These enhanced materials demonstrated improved reliability, reduced thermal expansion, and maintained performance after rigorous testing.
Area of Science:
- Materials Science
- Polymer Science
- Optoelectronics
Background:
- Packaging materials significantly influence the performance and reliability of light-emitting diodes (LEDs).
- Epoxy encapsulants are commonly used but can be susceptible to environmental degradation, affecting device longevity.
Purpose of the Study:
- To enhance the performance and reliability of LED devices by incorporating filler powders into epoxy packaging materials.
- To evaluate the effects of various inorganic silica fillers (quartz, fused silica, cristobalite, spherical silica) and an organic filler (spherical silicone powder) on epoxy properties and LED device reliability.
Main Methods:
- Epoxy materials incorporated with different fillers were used to encapsulate LED devices.
- Reliability was assessed through moisture saturation, high-temperature solder reflow, and thermal cycling tests.
- Material properties were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), thermomechanical analyzer (TMA), UV-vis spectrophotometry, scanning acoustic microscopy (SAM), and scanning electron microscopy (SEM).
Main Results:
- Inorganic silica-filled epoxy systems exhibited lower water sorption and diffusion coefficients compared to unfilled epoxy.
- Addition of fillers, particularly quartz, fused silica, and spherical silica, significantly reduced the coefficient of thermal expansion (CTE) both below and above the glass transition temperature (Tg).
- No delamination or internal cracking was observed in the enhanced LED devices after harsh environmental testing; modulus at room temperature increased with filler addition.
Conclusions:
- Incorporating inorganic silica fillers into epoxy packaging effectively improves the moisture resistance and thermal-mechanical properties of LED devices.
- The enhanced packaging materials contribute to superior reliability, preventing failures like delamination and cracking under thermal stress.
- Specific silica fillers offer significant advantages in reducing CTE, crucial for long-term LED device stability and performance.
