LED Package Encapsulant Composite to Prevent Resin Cracking

The patent applies composite materials by combining the light transmissive resin with reinforcing fillers (such as glass fibers, silica, or alumina) to create a composite encapsulant. This composite structure provides both the light transmissive properties needed for LED operation and the mechanical strength to resist cracking from thermal expansion mismatch. The reinforcing fillers form a network within the resin matrix that prevents crack propagation while maintaining optical transparency.

The patent changes the physical and chemical parameters of the encapsulant material by selecting resins with specific glass transition temperatures, molecular weights, and crosslinking densities. These parameter adjustments optimize the resin's thermal expansion coefficient to better match the LED chip, reducing thermal stress. The reinforcing fillers further modify parameters such as tensile strength, elongation at break, and thermal conductivity to prevent cracking while maintaining reliability.

The patent applies local quality by strategically selecting filler materials and distributions that provide crack resistance only where needed (in the structural matrix) while maintaining optical clarity in the light transmission path. The reinforcing fillers are dispersed throughout the resin matrix to provide mechanical strength, but their concentration and type are optimized to minimize light scattering and absorption. Different filler materials (glass fibers, silica, alumina) are chosen based on their specific optical and mechanical properties to balance these requirements.

The patent employs inexpensive, inert filler materials such as glass fibers, silica, and alumina that provide durable mechanical reinforcement without degrading over time. These fillers are selected for their chemical stability, low cost, and ability to maintain structural integrity under thermal cycling, while their optical properties (transparency or appropriate refractive index) ensure they do not significantly impede light transmission or reduce luminous efficacy.