VCSEL Driving Wiring Layout for High-Density Light Emission
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Solution Overview
Problem
Existing light emitting devices face challenges in achieving high density and output of individually drivable light emitting elements due to limited space for driving wirings and high current injection requirements, which complicates the arrangement of VCSEL elements.
Innovation Solution
The device is configured with multiple groups of VCSEL elements, each connected to separate driving wirings that overlap and are electrically isolated by an insulating layer, allowing for individual control and increased current injection capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of driving wirings is increased to individually control more light emitting regions, then the distance measurement performance is improved, but the space for laying down driving wiring is insufficient and the device complexity increases
Solution Approach 1:
Multiple driving wirings are merged into a single plane and extended to overlap with each other. The wirings are electrically isolated by an insulating layer while sharing the same spatial region, thereby reducing the overall space required for wiring layout and simplifying the device structure.
Solution Approach 2:
The patent transitions from a two-dimensional wiring layout to a three-dimensional configuration by extending driving wirings in the thickness direction to overlap. This allows multiple wirings to coexist in the same planar space at different heights, effectively increasing wiring capacity without expanding the device footprint.
2Reliability
If the width of interconnection is increased to increase limiting current density and avoid electromigration, then the reliability is improved, but the space for arranging light emitting elements at high density is reduced
Solution Approach 1:
The patent utilizes the thickness direction to create overlapping wiring layers. This three-dimensional wiring arrangement increases the effective cross-sectional area for current flow without expanding the planar footprint, thereby maintaining high current capacity and electromigration resistance while preserving high light emitting element density.
Solution Approach 2:
Multiple driving wirings are nested within each other in the thickness direction, with each wiring positioned at a different height level. This nested configuration allows the wirings to share the same spatial envelope while maintaining electrical isolation, effectively increasing the total current carrying capacity without increasing the device area.
3Measurement precision
If VCSEL elements are arranged at high density with narrow pitch to improve distance measurement performance, then the measurement precision is improved, but the space for driving wirings becomes even more limited
Solution Approach 1:
By extending driving wirings in the thickness direction to create overlapping layers, the patent effectively moves wiring layout from a two-dimensional constraint to a three-dimensional solution. This allows high-density VCSEL arrangement in the plane while providing sufficient wiring space through vertical stacking.
Solution Approach 2:
The patent segments the driving wirings into multiple electrically isolated layers separated by insulating material. Each wiring layer can be independently routed to specific VCSEL groups, allowing flexible connection patterns that accommodate high-density element arrangement while maintaining adequate wiring separation and space.
Data Source
AI summary
A light emitting device includes a plurality of light emitting elements and a plurality of driving wirings for driving the plurality of light emitting elements. The plurality of light emitting elements are divided into a plurality of groups each including at least two light emitting elements, the plurality of driving wirings are provided corresponding to the plurality of groups, the plurality of driving wirings overlap each other at least a part thereof in a plan view, and is electrically separated from each other by an insulating layer, and each of the plurality of driving wirings is electrically connected to light emitting elements belonging to the corresponding group among the plurality of groups on upper surfaces of the light emitting elements.