Light Emitting Device Electrode Protrusion Design for Stress Relief
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The reliability of light emitting devices is compromised due to stress-induced gaps and silver migration between the semiconductor stacked body and electrodes, leading to electrical discontinuity and increased resistance.
Innovation Solution
A light emitting device design featuring a first electrode with a protrusion and depression structure on its lower surface, where the bonding member contacts only a part of the protrusion's side surface, reducing stress and preventing silver migration into gaps, thereby enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bonding member is used to electrically connect the lead and electrode, then electrical connectivity is achieved, but stress-induced gaps and silver migration occur between the semiconductor stacked body and electrodes
Solution Approach 1:
The lower surface of the first electrode is segmented into multiple protrusions (first protrusion, second protrusion, third protrusion) with depressions between them. This segmentation prevents continuous silver migration paths and reduces stress concentration, thereby suppressing gap formation while maintaining electrical connectivity through the bonding member that contacts the side surfaces of the protrusions.
Solution Approach 2:
Different regions of the electrode structure are given different heights and functions: the first protrusion has a greater height than the second and third protrusions, creating localized stress distribution. The bonding member contacts specific side surfaces (first side surface and third side surface) while the second side surface is separated, creating localized protection against silver migration in critical areas.
2Reliability
If the bonding member contacts the entire side surface of the protrusion, then electrical connectivity is maximized, but stress concentration increases leading to gap formation
Solution Approach 1:
The bonding member contacts only specific portions of the protrusion side surfaces (first side surface and third side surface) rather than the entire surface. This partial contact reduces stress concentration while maintaining sufficient electrical connectivity. The second side surface is intentionally separated from the bonding member to prevent stress-induced gap formation.
3Volume of moving object
If the depression width is small, then the electrode structure is compact, but silver migration can easily occur into the gap
Solution Approach 1:
The depression between protrusions is segmented into regions with different widths: the first depression (between first and second protrusions) has a width of not less than 5 μm to prevent silver migration, while the second depression (between second and third protrusions) has a smaller width for compactness. This segmented approach balances migration prevention with space efficiency.
Data Source
AI summary
According to one embodiment, a light emitting device includes a first lead, a light emitting element, and a first bonding member. The light emitting element includes a semiconductor stacked body and a first electrode. The semiconductor stacked body includes a light emitting layer. The first electrode is below the semiconductor stacked body. The first bonding member electrically connects the first lead and the first electrode. A lower surface of the first electrode includes a first protrusion, a second protrusion, and a first depression. The first depression is located between the first and second protrusions. The first protrusion has a first side surface. The second protrusion has a second side surface facing the first side surface. The first bonding member contacts at least a part of the first side surface. At least a part of the second side surface is separated from the first bonding member.