Ultrathin Metal Layers in Flex PCBs for Tensile Strength
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Solution Overview
Problem
Printed circuit board traces fail due to repeated mechanical deformation, particularly under tension forces, leading to device degradation or failure, as existing solutions often rely on bulky secondary reinforcements that compromise flexibility.
Innovation Solution
Incorporating one or more ultrathin metal layers within the printed circuit board stack, which act as structural elements to absorb mechanical loads and enhance tensile strength, thereby reducing the risk of trace failure during deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If bulky secondary reinforcements are used to strengthen the circuit board, then the tensile strength and reliability are improved, but the flexibility and device complexity are worsened
Solution Approach 1:
The patent applies this principle by using thin metal layers (such as stainless steel or other metallic films) integrated within the flexible circuit board structure. These thin metallic layers provide the necessary tensile strength and mechanical reinforcement without the bulkiness of traditional reinforcement methods, thereby maintaining the flexibility and bendability of the circuit board while improving its reliability under repeated deformation
Solution Approach 2:
The patent employs composite materials by combining flexible substrate materials (such as polyimide or polyester) with thin metal layers to create a multi-layer composite structure. This composite approach allows the circuit board to achieve enhanced mechanical strength and tensile properties while preserving flexibility, as the metal layers are strategically positioned and bonded to the flexible substrate to provide reinforcement only where needed
2Reliability
If metal layers are added to enhance mechanical robustness, then the reliability and tensile strength are improved, but the flexibility and ease of operation are worsened
Solution Approach 1:
The patent uses thin metallic films or layers that are sufficiently flexible to allow the circuit board to bend and deform repeatedly. These thin metal layers are integrated into the flexible circuit board structure in a manner that provides mechanical reinforcement during bending operations, thereby improving reliability without significantly compromising the flexibility and ease of operation of the overall device
Solution Approach 2:
The patent applies parameter changes by carefully controlling the thickness, material composition, and structural configuration of the metal layers. By optimizing these parameters, the metal layers provide enhanced mechanical robustness and reliability while maintaining the flexibility required for repeated bending and deformation operations
3Strength
If conventional reinforcement methods are used, then the strength is improved, but the manufacturing complexity and productivity are worsened
Solution Approach 1:
The patent employs composite material construction where thin metal layers are laminated or bonded to flexible substrate materials using conventional manufacturing techniques. This approach allows for the production of reinforced flexible circuit boards through established processes such as lamination, printing, and bonding, thereby achieving enhanced strength without significantly increasing manufacturing complexity or reducing productivity
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A printed circuit board is provided. The printed circuit board includes a flexible region. The flexible region includes a first copper layer, a first dielectric layer, a second copper layer, an adhesive layer, and a first metal layer, in the order listed. The first metal layer includes a metal film having a tensile strength greater than the first and second copper layers and greater than the dielectric layer.