Flip-Chip LED Barrier Structure Against Edge Short-Circuits
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Solution Overview
Problem
Current semiconductor LEDs have low light-emitting efficiency due to energy waste and are prone to short-circuits caused by insulating layer damage during chip cutting and solder paste overflow, which affects package yield and reliability.
Innovation Solution
A flip-chip LED chip design featuring a barrier structure at the epitaxial layer edge, formed by etching openings that expose the substrate surface, creating a protective barrier to prevent short-circuits and improve reliability, along with a fabrication method that includes depositing an insulating layer and forming metal electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional insulating layer is used at the chip edge, then the chip structure is simple, but the insulating layer is prone to breaking during chip cutting causing short-circuits
Solution Approach 1:
The patent applies preliminary action by forming a barrier structure at the chip edge before the insulating layer is deposited. This pre-formed barrier structure provides mechanical support and protection to the insulating layer during subsequent chip cutting processes, preventing the insulating layer from breaking and causing short-circuits between P and N electrodes.
Solution Approach 2:
The patent segments the chip structure by dividing it into an epitaxial bulk layer and a barrier structure at the edge. This segmentation creates a distinct protective region that isolates the vulnerable insulating layer from mechanical stress during cutting, thereby improving reliability without significantly complicating the overall device structure.
2Ease of manufacture
If solder paste welding is used for large size chip, then the packaging process is simple, but solder paste overflows causing uneven coating and electric leakage
Solution Approach 1:
The barrier structure acts as an intermediary element between the solder paste and the insulating layer. It provides a physical barrier that guides and contains the solder paste within the intended welding area, preventing overflow onto the insulating layer and subsequent electric leakage, while maintaining the simplicity of the solder paste welding process.
Solution Approach 2:
The patent applies preliminary anti-action by creating a barrier structure that preemptively counteracts the harmful effect of solder paste overflow. This barrier structure is designed to intercept and contain the solder paste before it can reach and damage the insulating layer, thus preventing electric leakage before it occurs.
3Reliability
If the insulating layer is made thicker to prevent breaking, then chip reliability improves, but the chip size increases and manufacturing complexity increases
Solution Approach 1:
The patent segments the protective function by separating it into two components: a thin insulating layer and a structural barrier. The barrier structure provides mechanical strength and protection during cutting, allowing the insulating layer to remain thin while still preventing short-circuits, thus avoiding the need to increase chip size.
Solution Approach 2:
The patent employs a composite structure combining the insulating layer with a barrier structure made from the epitaxial layer material. This composite approach provides both electrical insulation and mechanical protection in a compact configuration, achieving high reliability without increasing chip dimensions.
Data Source
AI summary
A flip-chip light emitting diode (LED) includes: a sapphire substrate having an edge; an epitaxial layer over the substrate, wherein the epitaxial layer comprises: a first semiconductor layer, a second semiconductor layer, and a light emitting layer between the first semiconductor layer and the second semiconductor layer, wherein the epitaxial layer is divided into an epitaxial bulk layer and a barrier structure; and an insulating layer over the epitaxial bulk layer, wherein a portion of the insulating layer that covers a sidewall of the epitaxial bulk layer is separated from the edge of the substrate by the barrier structure.