Multilayer Board Step Portion Peeling Prevention
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Solution Overview
Problem
Existing multilayer boards experience peeling issues when the flexible portion is bent due to the difference in thickness between rigid and flexible portions, leading to stress and potential interlayer peeling.
Innovation Solution
A multilayer board configuration where a third resin base material portion is strategically placed between the first and second resin base material portions to create a step portion, ensuring the first and second resin base materials extend beyond this step, preventing exposed joined surfaces and reducing interlayer peeling, while allowing for adjustable thickness and rigidity through varying the number of laminated resin layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the rigid portion is increased by laminating multiple resin sheets, then the rigidity and strength of the rigid portion is improved, but the flexibility and flexibility of the flexible portion deteriorates
Solution Approach 1:
The multilayer board is divided into distinct rigid portions and a flexible portion with different numbers of laminated resin sheets. The rigid portions have multiple resin sheets laminated to achieve high rigidity, while the flexible portion has fewer resin sheets to maintain flexibility and bendability, resolving the contradiction between rigidity and flexibility through spatial segmentation.
Solution Approach 2:
Different regions of the multilayer board are assigned different local qualities in terms of resin sheet lamination. The rigid portions have high lamination density for strength, while the flexible portion has low lamination density for flexibility. This local differentiation allows each region to optimize its mechanical properties according to functional requirements.
2Strength
If the number of laminated resin sheets is increased in the rigid portion, then the thickness and rigidity are improved, but the likelihood of interlayer peeling at the step portion increases
Solution Approach 1:
The resin sheets in the flexible portion are extended in advance beyond the step portion toward the rigid portions. This preliminary extension creates a gradual transition and distributes stress at the step portion, preventing sudden stress concentration that would cause peeling. The extended resin sheets act as stress-dispersing elements before the thickness change occurs.
Solution Approach 2:
The extended resin sheets in the flexible portion serve as an intermediary element between the flexible and rigid portions. These extended sheets bridge the step portion, providing a gradual transition in thickness and distributing mechanical stress. This intermediary structure prevents direct stress concentration at the step edge, thereby preventing peeling while maintaining the rigidity advantage of the multi-layered rigid portions.
3Adaptability or versatility
If different resin materials with different thermal expansion coefficients are used, then the material selection flexibility is improved, but the occurrence of interlayer peeling due to thermal expansion difference increases
Solution Approach 1:
The patent specifies that all resin base materials in the multilayer board are made from the same thermoplastic resin. This homogeneity ensures uniform thermal expansion coefficients across all layers, preventing thermal stress and interlayer peeling during temperature changes. The homogeneous material selection simplifies the design process while ensuring thermal compatibility.
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
Significantly reduces or prevents peeling when the flexible portion is bent, enhances connection reliability, and allows for flexible design options by maintaining uniform material properties and minimizing thermal expansion coefficient differences.
Implementation Method 1
it is possible to integrate the resin base material portions through a simple process using a heating press
Implementation Method 2
the resin base materials are fused thus to be joined together
Data Source
AI summary
In a flexible board including laminated resin layers containing the same thermoplastic resin as a principal material, a rigid portion includes a region in which a first resin layer is disposed between a second resin layer defining an upper principal surface and a third resin layer defining a lower principal surface so that the rigid portion has a large thickness, and a flexible portion includes a region in which the first resin layer is not disposed between the second and third resin layers so that the flexible portion has flexibility, a step portion at which a thickness changes is between the rigid and flexible portions, and the second and third resin layers extend in a region from the rigid portion beyond the step portion to the flexible portion.