Opto-electric Hybrid Board Waveguide Anchoring
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Solution Overview
Problem
Opto-electric hybrid boards face issues with peeling off of optical waveguides due to stress differences between materials, particularly at corner portions, leading to warpage and distortions, which affects their flexibility and longevity in electronic devices.
Innovation Solution
The design involves forming openings or recesses in the metal or insulation layers to anchor the optical waveguide, reducing stress concentrations and increasing peel strength by direct contact with the underlying layer, thereby preventing peeling off during manufacturing and usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the optical waveguide W is directly stacked on the insulation layer 1, then the structure is simple, but the difference in coefficient of linear expansion causes stresses and bending in the optical waveguide W due to ambient temperature, resulting in increased light propagation losses
Solution Approach 1:
A metal layer 9 is introduced as an intermediary between the insulation layer 1 and the optical waveguide W. This metal layer serves as a stress compensation layer that absorbs thermal expansion differences, preventing stresses and bending in the optical waveguide W while maintaining structural simplicity.
2Reliability
If the metal layer 9 is provided between the insulation layer 1 and the optical waveguide W, then light propagation losses are avoided, but the flexibility of the opto-electric hybrid board decreases
Solution Approach 1:
The metal layer 9 is segmented by providing through holes 5 and 5′ that penetrate through it. This segmentation maintains the stress compensation function while allowing the optical waveguide W to pass through and enabling the board to bend, thus restoring flexibility.
3Adaptability or versatility
If the opto-electric hybrid board is designed with increased flexibility by removing metal layers, then flexibility is improved, but the optical waveguide W peels off in corner portions P due to stress concentration
Solution Approach 1:
The metal layer 9 is strategically retained at opposite end portions where flexibility is less critical, while being removed from intermediate portions. This preliminary arrangement prevents stress concentration at corner portions P of the optical waveguide W, avoiding peeling while maintaining necessary flexibility in the board.
4Adaptability or versatility
If the optical waveguide W is disposed directly on the back surface of the insulation layer 1 without metal layers, then flexibility is maximized, but the optical waveguide W peels off in corner portions P due to material stress differences
Solution Approach 1:
The metal layer 9 is selectively provided only at opposite end portions of the opto-electric hybrid board where structural support is needed, while being absent from intermediate portions. This local quality approach provides stress compensation where necessary while maximizing flexibility in other areas, preventing peeling at corner portions P.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the durability and flexibility of opto-electric hybrid boards by reducing peeling off and warpage, allowing them to be used over a prolonged period without significant stress-induced distortions.
Implementation Method 1
an optical waveguide W includes three layers: an under cladding layer 6; a core 7 serving as an optical path; and an over cladding layer 8
Data Source
AI summary
An opto-electric hybrid board includes: an electric circuit board including an insulation layer and electrical interconnect lines formed on the front surface of the insulation layer; and an optical waveguide provided on the back surface side of the insulation layer of the electric circuit board, with a metal layer therebetween. At least one opening is formed by removing at least part of a region of the metal layer which is overlaid on the contour of an end portion of the optical waveguide. The optical waveguide is formed, with part of the optical waveguide extending into the opening. The opto-electric hybrid board is favorably usable over a prolonged period because the end portion of the optical waveguide provided on the back surface side of the electric circuit board does not peel off the metal layer.