Multilayer Resin Substrate Bending Stress Management
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Solution Overview
Problem
Conventional multilayer resin substrates experience cracking of the protective layer during bending, which leads to cracking of the conductor pattern and variations in electrical characteristics due to applied bending stress.
Innovation Solution
A multilayer resin substrate configuration where the conductor pattern is positioned inside the stacked body at bent portions, and the protective layer covers these areas, reducing stress on the conductor pattern and preventing cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the protective layer is provided on the surface of the stacked body covering the conductor pattern, then the conductor pattern is protected, but large bending stress causes cracks in the protective layer and conductor pattern
Solution Approach 1:
The substrate is divided into a bent portion and a non-bent portion, with the conductor pattern selectively positioned only in the non-bent portion. This segmentation allows the protective layer to cover the conductor pattern for protection while the bent portion can deform without cracking the protective layer, as no conductor pattern exists there to crack.
Solution Approach 2:
The conductor pattern is selectively located only in the non-bent portion of the substrate, creating local quality differentiation. This means the protective layer provides protection where needed (over the conductor pattern in the non-bent portion) while allowing the bent portion to flex without stress concentration on conductors, preventing cracks.
2Ease of operation
If the conductor pattern is provided on the surface of the stacked body, then electrical connections are established, but bending stress causes cracking and variations in electrical characteristics
Solution Approach 1:
The substrate is segmented into bent and non-bent portions, with conductor patterns exclusively in the non-bent portion. This ensures electrical connections are established on the surface where needed, while the bent portion flexes without stressing the conductors, maintaining electrical characteristic stability.
3Reliability
If the protective layer is made rigid to protect the conductor pattern, then protection is improved, but flexibility of the multilayer resin substrate is reduced
Solution Approach 1:
The substrate structure is segmented such that the protective layer covers only the non-bent portion containing the conductor pattern. This provides rigid protection where needed while the bent portion remains flexible and can deform without the protective layer imposing rigidity constraints, maintaining overall substrate adaptability.
Solution Approach 2:
The protective layer provides localized rigid protection only in the non-bent portion where the conductor pattern exists, while the bent portion maintains its flexibility. This local quality differentiation allows the substrate to be rigid where protection is needed and flexible where deformation is required.
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 significantly reduces cracking and variations in electrical characteristics while allowing for easier manufacturing and improved mountability by distributing bending stress effectively.
Implementation Method 1
The protective layer, after the stacked body is provided, is provided by being applied (or attached) to the surface of the stacked body and then being heated and cured
Data Source
AI summary
A multilayer resin substrate includes a stacked body including first resin layers made of a thermoplastic resin, conductor patterns on the stacked body, and a protective layer including a second resin layer made of a thermosetting resin. The stacked body includes first and second main surfaces, and a bent portion. One of the conductor patterns located at the bent portion is located only inside the stacked body. The protective layer covers at least the bent portion, on the main surface of the stacked body.