Flexible Circuit Board with Slippage Layer for Bending Stress
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Solution Overview
Problem
Existing circuit boards with laminated ceramic layers are prone to detachment from printed wiring boards due to impact-induced bending, as they do not deform to follow the bending of the wiring board, leading to solder breakage and separation.
Innovation Solution
A circuit board with laminated insulating material layers and a slippage occurrence layer between them, where the internal conductor extends across regions connecting external electrodes, is designed to prevent detachment by allowing flexibility and slippage, thereby distributing stress and preventing solder breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a circuit board is made from hard laminated ceramic layers, then structural strength is improved, but the board cannot deform to follow bending of the printed wiring board, causing solder breakage and detachment
Solution Approach 1:
The circuit board is divided into multiple rigid ceramic layers (first through fourth ceramic layers) separated by flexible resin layers. This segmentation allows each ceramic layer to maintain structural strength while the flexible resin layers between them provide deformation capability, enabling the board to follow bending of the printed wiring board without causing solder breakage.
Solution Approach 2:
The circuit board uses a composite structure combining rigid ceramic materials (for strength) with flexible resin materials (for deformability). This composite construction allows the board to simultaneously achieve high structural strength from the ceramic layers and bending flexibility from the resin layers, resolving the contradiction between strength and connection reliability.
2Reliability
If sheets made of flexible material are laminated to produce the circuit board, then the board can bend to follow the printed wiring board, but the electronic component may detach due to load on external electrodes
Solution Approach 1:
The flexible resin layers are positioned specifically between ceramic layers rather than making the entire circuit board flexible. This segmentation allows the board to bend at the resin layer interfaces while the ceramic layers with external electrodes remain relatively rigid, preventing excessive deformation and load on the electrode connections.
Solution Approach 2:
Different parts of the circuit board have different mechanical properties: the ceramic layers provide local rigidity and strength where electrodes are located, while the resin layers provide local flexibility in the intermediate regions. This local quality differentiation allows the board to bend without subjecting the electrode connections to damaging loads.
3Reliability
If the circuit board is made completely flexible, then detachment from printed wiring board is prevented, but stress concentration occurs at the electronic component connection points
Solution Approach 1:
The circuit board is segmented into rigid ceramic sections and flexible resin sections. The flexible resin layers enable overall board bending to prevent detachment, while the rigid ceramic layers with external electrodes act as stress-distributing elements that prevent stress concentration at the electrode connection points with electronic components.
Data Source
AI summary
In a circuit board, a laminate includes a plurality of laminated insulating material layers made of a flexible material. First external electrodes are provided on an upper surface of the laminate, and an electronic component is mounted thereon. Second external electrodes are provided on a lower surface of the laminate and mounted on a wiring board. An internal conductor is provided between first and second adjacent insulating material layers, fixed to the first insulating material layer, and not fixed to the second insulating material layer. The internal conductor is arranged so as to extend across regions obtained by connecting certain ones of the second external electrodes to certain ones of the first external electrodes located closest to the certain ones of the second external electrodes.