Flexible Wiring Circuit Board Shield Layer Design
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Solution Overview
Problem
Flexible wiring circuit boards face challenges in achieving both excellent adhesive properties and effective electromagnetic wave shielding, particularly when deformed, as existing shield films fail to provide sufficient adhesion and shielding.
Innovation Solution
A flexible wiring circuit board structure is developed, featuring a shield layer with an electrically conductive layer from group 11 and barrier layers from groups 4 to 10, sandwiched between insulating layers, which includes polyimide materials and specific metals like titanium, chromium, nickel, and tantalum to enhance adhesion and prevent metal migration, allowing direct contact between layers for reduced thickness and improved shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a shield film including adhesive film formed from SUS on a resin board is used, then electromagnetic wave shielding is achieved, but adhesive properties deteriorate when the flexible wiring circuit board is deformed
Solution Approach 1:
The shield layer is constructed as a composite structure with multiple metal layers (first barrier layer, electrically conductive layer, second barrier layer) deposited on the resin board. This composite structure combines the electromagnetic shielding effectiveness of conductive metals with the adhesive bonding capabilities of the resin board, achieving both shielding and adhesion requirements simultaneously.
2Strength
If the shield layer uses stainless steel (SUS) for both adhesion and shielding, then structural integrity is maintained, but both adhesive properties and shield properties are insufficient
Solution Approach 1:
Different regions of the shield layer are assigned different metal materials with specific local functions: the first and second barrier layers use metals with excellent adhesive properties to the resin board, while the electrically conductive layer uses metals with superior electromagnetic shielding characteristics. This local differentiation of material properties enables both adhesion and shielding to be optimized independently.
3Reliability
If barrier layers from groups 4 to 10 and periods 4 to 6 are used, then adhesive properties and shield properties are improved, but device complexity increases
Solution Approach 1:
The shield layer is segmented into three distinct metal layers, each with specific thicknesses and material compositions. The first barrier layer (0.01-0.1 μm), electrically conductive layer (0.03-0.5 μm), and second barrier layer (0.01-0.1 μm) are deposited sequentially, with each layer performing a specific function. This segmentation allows independent optimization of adhesion and shielding properties while maintaining a manageable overall structure.
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 achieves both excellent adhesive properties and electromagnetic wave shielding, ensuring the shield layer adheres without adhesives and efficiently grounds the shield layer, reducing the circuit board's thickness while maintaining effective shielding properties.
Implementation Method 1
the barrier layer is selected from a metal belonging to groups 4 to 10, and the fourth to the sixth periods in the periodic table... the spread (migration) of the metal that is the material for the shield layer in the second insulating layer and the third insulating layer whose materials are the polyimide can be suppressed
Implementation Method 2
a shield layer of the electromagnetic waves is provided in the circuit board, and the electromagnetic waves are shielded from the outside
Data Source
AI summary
A flexible wiring circuit board includes a first insulating layer, a wire disposed at one side in a thickness direction of the first insulating layer, a second insulating layer disposed at one side in the thickness direction of the wire, a shield layer disposed at one side in the thickness direction of the second insulating layer, and a third insulating layer disposed at one side in the thickness direction of the shield layer. The shield layer includes an electrically conductive layer and two barrier layers sandwiching the electrically conductive layer therebetween in the thickness direction. The electrically conductive layer is selected from a metal belonging to a group 11, and the fourth period and the fifth period in the periodic table, and the barrier layer is selected from a metal belonging to groups 4 to 10, and the fourth to the sixth periods in the periodic table.