Flexible Wiring Circuit Board Warping Suppression
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Solution Overview
Problem
Conventional flexible wiring circuit boards with reduced thickness are prone to warping due to the thinness of the insulating and cover layers, and the absence of a metal supporting body exacerbates this issue.
Innovation Solution
A flexible wiring circuit board design featuring a first insulating layer with a hygroscopic expansion coefficient of 15×10−6/% RH or less, a conductive pattern exposed from the insulating layers, and a total thickness of 16 μm or less, along with an optional shield layer and additional insulating layers, to minimize warping and achieve thickness reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the total thickness of the insulating layer and the cover layer is reduced, then the thickness of the wiring circuit board is reduced, but warping easily occurs
Solution Approach 1:
The patent applies parameter changes by selecting insulating materials with specific hygroscopic expansion coefficients (15×10−6/% RH or less) and controlling the total thickness of insulating layers to 16 μm or less. This resolves the contradiction by changing the material parameter (hygroscopic expansion coefficient) to maintain stability while reducing thickness.
Solution Approach 2:
The patent uses composite materials by combining multiple insulating layers (first insulating layer, second insulating layer, and optionally third insulating layer) with different thicknesses and material properties. The first insulating layer has a hygroscopic expansion coefficient of 15×10−6/% RH or less, while the second layer may have different properties, creating a composite structure that reduces overall thickness while maintaining warping resistance through balanced material composition.
2Stability of the object's composition
If a metal supporting body is added to suppress warping, then warping is suppressed, but the thickness reduction benefit is compromised
Solution Approach 1:
The patent applies the extraction principle by removing the metal supporting body from the conventional structure. Instead of using a metal supporting body to prevent warping, the invention extracts this component and replaces it with insulating layers having controlled hygroscopic expansion coefficients, thereby achieving warping suppression without the additional thickness that would result from adding a metal support layer.
Solution Approach 2:
The patent changes the approach to warping suppression by modifying the hygroscopic expansion coefficient parameter of the insulating materials rather than adding a metal supporting body. By selecting materials with hygroscopic expansion coefficients of 15×10−6/% RH or less and optimizing layer thicknesses, the patent achieves warping resistance while maintaining the thin profile without requiring additional metal support layers.
3Stability of the object's composition
If the insulating material has low hygroscopic expansion coefficient, then warping is suppressed, but material selection becomes more restricted
Solution Approach 1:
The patent applies parameter changes by establishing a specific threshold for the hygroscopic expansion coefficient (15×10−6/% RH or less) that balances warping suppression with manufacturing feasibility. This parameter setting resolves the contradiction by defining a clear specification that ensures adequate warping resistance while maintaining reasonable material selection flexibility for production.
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 effectively reduces warping and achieves a thinner profile while maintaining connection reliability, suitable for applications like imaging devices.
Implementation Method 1
at least the first insulating layer contains an insulating material having a hygroscopic expansion coefficient of 15×10−6/% RH or less
Data Source
AI summary
A mounted board includes a base insulating layer, a conductive pattern, and a cover insulating layer sequentially toward one side in a thickness direction. The entire lower surface of the base insulating layer is exposed downwardly. A total thickness of the base insulating layer and the cover insulating layer is 16 μm or less. The base insulating layer contains an insulating material having a hygroscopic expansion coefficient of 15×10−6/% RH or less.