Solid State Light Emitting Device Edge Stress Relief
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Solution Overview
Problem
The manufacturing process of solid state light emitting devices, such as LEDs, often results in stress-related defects like delamination and cracking due to low adhesion between metal and semiconductor layers, particularly during the separation and packaging stages.
Innovation Solution
The introduction of stress-relief elements and anchor elements in the edge regions of the metallization and dielectric layers, formed by varying the thickness or creating holes in the guard and dielectric layers, helps to reduce stress and improve adhesion, thereby minimizing die edge defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple devices are formed on a single substrate and then separated, then productivity is improved, but stress-induced delamination and cracking occur during separation and packaging
Solution Approach 1:
The patent divides the continuous metallization layer into discrete segments by introducing trenches at regular intervals. This segmentation allows the structure to accommodate stress during separation and packaging without causing delamination or cracking, while still maintaining electrical connectivity where needed.
Solution Approach 2:
The patent applies different properties to different regions of the metallization layer. Trenches are strategically placed in regions where stress concentration is expected during separation, creating local variations in structural integrity that prevent catastrophic failure while maintaining overall functionality.
2Device complexity
If thin metallization layers are used, then device complexity is reduced, but adhesion between metal and semiconductor layers deteriorates
Solution Approach 1:
The patent performs preliminary stress relief by introducing trenches into the metallization layer before the separation and packaging processes occur. This preemptive structural modification prevents stress accumulation that would otherwise lead to delamination during subsequent manufacturing steps.
Solution Approach 2:
The trenches act as intermediary stress-absorbing features between the metallization layer and the semiconductor layers. They provide a controlled mechanism for stress release, preventing direct stress transmission that would cause adhesion failure between the metal and semiconductor interfaces.
3Manufacturing precision
If deep trenches are formed through metallization and semiconductor layers, then separation precision is improved, but manufacturing complexity increases
Solution Approach 1:
The patent forms trenches that extend partially through the metallization layer and semiconductor layers, but not necessarily through the entire device structure. This partial penetration provides sufficient stress relief and separation definition without requiring complete traversal of all layers, reducing manufacturing complexity while maintaining precision.
Data Source
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AI summary
A solid state light emitting device includes a light emitting stack (20), a metallization (30), comprising a guard layer (36) of metal,and a dielectric layer (50) over the guard layer (36) of the metallization. During subsequent processing delamination and/or cracking may occur at the edges of the devices, sometimes referred to as die edge defects. To address these defects a plurality of stress-relief elements (62, 64) and/or anchor elements may be provided in an edge region of the metallization and/or dielectric layer for reducing delamination. The stress-relief elements (62, 64) are formed by regions of reduced thickness or increased thickness in the guard layer (36).