Flex-Rigid Wiring Board Via Structure
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Solution Overview
Problem
Existing flex-rigid wiring boards face challenges in reliably connecting flexible and rigid substrates due to stress transmission and manufacturing complexity, particularly in maintaining high reliability and heat resistance while minimizing material usage and costs.
Innovation Solution
A flex-rigid wiring board design featuring a flexible substrate with a conductor pattern, a non-flexible substrate, an insulating layer exposing portions of the flexible board, and a plating layer connecting conductor patterns through via holes formed in the insulating layer, which reduces stress transmission and enhances reliability by using a resin-filled via structure and prepreg materials for bonding and insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the flexible board is bonded to the rigid substrate with adhesive and bulk conductors, then electrical connection is achieved, but the connection reliability deteriorates under bending stress
Solution Approach 1:
The patent uses a flexible board with conductor patterns formed directly on flexible substrate, replacing rigid adhesive-bonded structures. The flexible board can bend without compromising connection reliability, as the conductor patterns are integrated into the flexible substrate itself rather than being bonded separately. This resolves the contradiction by making both the connection structure and the supporting structure flexible and stress-resistant.
Solution Approach 2:
The patent creates a composite structure where the flexible board (with conductor patterns) and rigid substrate are connected through insulating adhesive with via openings. The via openings are filled with plating material to create conductive pathways. This composite structure allows the flexible board to maintain electrical connection reliability while independently handling bending stresses, preventing stress transmission to the connection points.
2Reliability
If specialized materials and processes are used for flex-rigid wiring boards, then connection reliability improves, but manufacturing cost increases
Solution Approach 1:
The flexible board serves multiple functions: it provides mechanical support, electrical connection pathways (through its conductor patterns), and stress absorption. By integrating these functions into a single flexible board component, the patent eliminates the need for separate adhesive layers and bulk conductors, simplifying manufacturing and reducing costs while maintaining connection reliability.
Solution Approach 2:
The patent replaces the mechanical adhesive-bonded connection system with an integrated flexible board system where conductor patterns are formed directly on the flexible substrate. This substitution eliminates complex bonding processes and specialized materials, allowing use of standard flexible substrate and conductor deposition processes, thereby reducing manufacturing cost while maintaining or improving reliability.
3Ease of manufacture
If the flexible board is disposed on one side of the rigid substrate, then assembly is simplified, but stress concentration occurs at connection points
Solution Approach 1:
The patent changes the structural parameters by forming via openings in the insulating adhesive layer and filling them with plating material. This creates distributed stress pathways through the insulating layer rather than direct point-to-point connections. The via openings act as stress distributors, reducing stress concentration at connection points while maintaining the simplified single-side assembly configuration.
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
The solution improves the reliability and heat resistance of the connection between flexible and rigid substrates, maintains high reliability similar to conventional rigid boards, and reduces manufacturing costs by minimizing material usage and simplifying the manufacturing process.
Implementation Method 1
a plating layer connecting the conductor pattern of the flexible board and the conductor pattern on the insulating layer
Implementation Method 2
a via formed in the insulating layer and connecting the conductor pattern on the insulating layer and the conductor pattern of the flexible board
Data Source
AI summary
A method of manufacturing a flex-rigid wiring board includes disposing a non-flexible substrate and a flexible board side by side in the horizontal direction of the substrate and board such that an end of the substrate is positioned adjacent to an end of the board and forms boundary between the board and the substrate with respect to the end of the board, covering the boundary between the board and the substrate with an insulating layer such that the insulating layer is positioned on the board and the substrate across the boundary, forming a second conductor pattern on the insulating layer, forming a via hole which passes through the insulating layer and reaches a first conductor pattern of the board, and plating the via hole such that a via conductor connecting the first and second patterns. The flexible board includes a flexible substrate and the first pattern formed over the substrate.