Bendable Wiring Substrate Structure for Stress-Balanced Reliability
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Solution Overview
Problem
Wiring substrates used in electronic devices face reliability issues when bent, as stress can cause breakage or deformation in the wiring and insulation layers, particularly at the bent portions.
Innovation Solution
A wiring substrate design with alternately stacked wiring and insulation layers, where the inner bent position has a higher elastic modulus insulation layer to absorb compressive stress and the outer bent position has a lower elastic modulus insulation layer to distribute tensile stress evenly, enhancing bending reliability and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the wiring substrate is made flexible to allow bending, then the adaptability and ease of operation are improved, but the reliability deteriorates due to stress-induced breakage or deformation of wiring and insulation layers
Solution Approach 1:
The patent applies local quality by differentiating the elastic modulus of insulation layers based on their position in the bent structure. The first insulation layer at the inner bent position has a higher elastic modulus to resist compressive stress, while the second insulation layer at the outer bent position has a lower elastic modulus to accommodate tensile stress. This localized differentiation of material properties resolves the contradiction between flexibility and reliability.
Solution Approach 2:
The patent uses composite materials by combining insulation layers with different elastic moduli in a stacked configuration. This composite structure allows the wiring substrate to simultaneously achieve flexibility for bending and reliability during bending operations, as each layer contributes its specific mechanical properties to handle the respective stress conditions at different positions.
2Ease of manufacture
If uniform insulation layers are used throughout the wiring substrate, then the manufacturing complexity is reduced, but the bending reliability deteriorates due to uneven stress distribution
Solution Approach 1:
The patent implements local quality by specifying that the first insulation layer at the inner bent position has a higher elastic modulus than the second insulation layer at the outer bent position. This localized differentiation addresses the stress distribution issue during bending while maintaining a relatively simple stacked structure that does not significantly complicate the manufacturing process.
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 design effectively limits deformation and breakage at the outer bent position, improving the bending reliability of the wiring substrate while maintaining flexibility, by distributing stress evenly across the structural body.
Implementation Method 1
The first insulation layer has a higher elastic modulus than the second insulation layer
Implementation Method 2
The second insulation layer is located at an outer bent position of the bendable portion relative to the first insulation layer when the bendable portion is bent
Data Source
AI summary
A wiring substrate includes a bendable portion including one or more wiring layers and insulation layers that are alternately stacked. The insulation layers of the bendable portion include a first insulation layer and a second insulation layer. The first insulation layer is located at an inner bent position of the bendable portion when the bendable portion is bent. The second insulation layer is located at an outer bent position of the bendable portion relative to the first insulation layer when the bendable portion is bent. The first insulation layer has a higher elastic modulus than the second insulation layer.