Rigid Flex Circuit for Hinge Signal Routing
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Solution Overview
Problem
Conveying signals between circuitry in the base and display of portable electronic devices is challenging due to bulky wiring harnesses or spiral flexible printed circuits, which can impose undesired stresses when the lid rotates relative to the base.
Innovation Solution
The use of a rigid flex printed circuit with a rigid printed circuit board portion in the base and lid, and a flexible printed circuit portion that traverses the hinge axis, minimizing stress through a neutral stress plane alignment and electromagnetic shielding to prevent interference between display and antenna signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bulky wiring harness or spiral flexible printed circuit is used to convey signals between the base and lid, then signal transmission is achieved, but the hinge structure becomes bulky and undesired stresses are imposed on the cables during rotation
Solution Approach 1:
The circuit board is segmented into a first circuit board portion mounted in the lid and a second circuit board portion mounted in the base, connected by a flexible circuit portion. This segmentation allows each portion to be independently positioned and connected, eliminating the need for bulky wiring harnesses while maintaining signal transmission reliability.
Solution Approach 2:
The flexible circuit portion is designed to accommodate the dynamic rotation between the lid and base. The flexible nature of this circuit portion allows it to bend and flex during hinge rotation without imposing undue stress, unlike rigid wiring harnesses or spiral flexible printed circuits.
2Adaptability or versatility
If a flexible printed circuit cable is wrapped in a spiral shape to allow rotation, then rotation is accommodated, but bulky hinge structures are required to provide sufficient space
Solution Approach 1:
The circuit connection is divided into rigid portions (first and second circuit board portions) and a flexible connecting portion. This segmentation allows the flexible portion to handle the rotation accommodation function while the rigid portions maintain structural integrity, eliminating the need for bulky spiral configurations.
Solution Approach 2:
The flexible circuit portion acts as a thin, flexible interconnection medium between the rigid circuit board portions. This flexible film structure accommodates rotation through its inherent flexibility without requiring the bulky spatial envelope of spiral cables, significantly reducing hinge structure volume.
3Reliability
If conventional wiring methods are used, then signal connection is established, but undesired stresses are imposed on cables during hinge rotation
Solution Approach 1:
The flexible circuit portion is specifically designed to dynamically accommodate hinge rotation without transmitting excessive stress to the connection points. Its flexibility allows it to absorb the mechanical stresses of rotation, preventing cable damage and maintaining connection reliability.
Solution Approach 2:
The flexible circuit portion serves as an intermediary element between the rigid circuit board portions, mediating the mechanical stresses of rotation. It absorbs and distributes these stresses in a controlled manner, preventing them from concentrating on the cable connections and compromising reliability.
Data Source
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AI summary
An electronic device may have a housing with a lid that rotates relative to a base. A display in the lid may have a thin-film transistor layer. Display driver circuitry may be mounted to the thin-film transistor layer. A display timing controller integrated circuit may be mounted in the base. A rigid flex printed circuit may have a rigid portion in the base to which the display timing controller integrated circuit is mounted and may have a rigid portion in the lid. A flexible printed circuit portion of the rigid flex printed circuit may be used to couple the rigid printed circuit portion in the lid to the thin-film transistor layer. A flexible printed circuit portion of the rigid flex printed circuit that extends between the lid and the base may be formed from a double-shield-layer single-signal-line-layer flexible printed circuit.