Raised Circuit Board Wiring for LED Electrode Protection
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Solution Overview
Problem
In light-emitting devices with flip-chip elements, the gap between the substrate and the element is often not properly filled with underfill, exposing electrodes and causing insufficient protection and reduced luminous flux due to exposed wiring with lower reflectance.
Innovation Solution
The implementation of raised portions on the circuit board wiring allows for effective filling with resin to protect the electrodes and application of a white or transparent resin to cover exposed wiring, preventing corrosion and enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the gap between the substrate and flip-chip light-emitting element is small, then the device structure is compact, but the underfill cannot properly fill the gap and electrodes are not sufficiently protected
Solution Approach 1:
The patent applies preliminary action by forming a resin protrusion on the substrate surface before mounting the light-emitting element. This protrusion pre-creates a filled state in the gap region, ensuring that when the element is mounted, the gap is already partially filled and electrodes are protected from the beginning, resolving the issue of insufficient underfill in compact designs
Solution Approach 2:
The resin protrusion acts as an intermediary structure between the substrate and the light-emitting element. It mediates the gap-filling function by providing a pre-formed resin structure that facilitates proper underfill distribution and ensures electrode protection without requiring a larger gap, thus resolving the contradiction between compact size and protection reliability
2Illumination intensity
If a white resin is applied to cover the substrate surface, then the reflectance is improved, but the wiring may be exposed in the vicinity of the light-emitting element causing decreased luminous flux
Solution Approach 1:
The patent applies local quality by making the resin protrusion location-specific and function-specific. The protrusion is formed only in the region where the light-emitting element will be mounted, providing local coverage that prevents wiring exposure in that specific area while allowing the white resin to be applied broadly for high reflectance. This resolves the contradiction by providing precise local protection where needed without compromising overall luminous flux
Data Source
AI summary
A light-emitting device includes a circuit board including a wiring on a surface of a substrate, the wiring including a raised portion, and a light-emitting element mounted on the raised portion. When the light-emitting element is of a flip-chip type, an element electrode thereof is connected to the raised portion such that an edge of the element electrode on an outer periphery side of the light-emitting element is located outside of the raised portion in a top view and an exposed portion of the element electrode is covered with a white or transparent resin. When the light-emitting element is of a face-up type, an element substrate thereof is bonded to the raised portion such that the raised portion is located inside the element substrate in the top view and an exposed portion of a bottom surface of the element substrate is covered with a white resin.