Flexible Board Ductile Metal Interlayer Stress Relief
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Solution Overview
Problem
Flexible multilayer boards face disconnection issues in conductor layers due to deformation, particularly when subjected to repeated stress, as the density variations during the multilayering process lead to uneven pressing forces and increased likelihood of disconnection.
Innovation Solution
The solution involves alternately stacking resin layers with conductor layers, where a second conductor layer made of a ductile metal like Co or Ni is interposed between the resin and a first conductor layer made of Cu, allowing the ductile metal to absorb stress, retard grain growth, and form an alloy that enhances the ductility and resistance to deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conductor layers are made thinner to reduce size and increase density, then the flexibility and space efficiency improve, but the likelihood of disconnection under repeated stress increases
Solution Approach 1:
The conductor layer is constructed as a composite structure with a first conductor layer (Cu) providing electrical conductivity and a second conductor layer (Co/Ni) providing mechanical strength and stress resistance. This composite approach allows thin overall thickness while maintaining both flexibility and connection reliability through the synergistic properties of different materials.
Solution Approach 2:
The second conductor layer made of Co or Ni is strategically positioned at the interface between the resin layer and the first conductor layer, where stress concentration occurs during bending. This local placement of high-strength material precisely where needed prevents disconnection without compromising overall flexibility.
2Quantity of substance
If multilayering process is used to increase density, then space efficiency improves, but variations in pressing force cause disconnection in conductor layers
Solution Approach 1:
The second conductor layer acts as a protective cushion layer that absorbs and distributes pressing forces during the multilayering process. This pre-positioned protective layer prevents stress concentration on the first conductor layer, thereby preventing disconnection before it can occur during manufacturing.
Solution Approach 2:
By changing the material parameter (ductility) of the conductor layer through the addition of Co or Ni, the layer becomes more resistant to deformation under pressing forces. This parameter change allows the conductor layer to withstand the mechanical stresses of multilayering while maintaining high density.
3Volume of moving object
If flexible board is designed to be bent many times for limited space application, then space efficiency improves, but repeated deformation causes disconnection in conductor layers
Solution Approach 1:
The conductor layer structure is designed to dynamically respond to bending stresses. The second conductor layer with superior ductility undergoes elastic deformation during bending cycles, absorbing mechanical energy and protecting the first conductor layer from permanent damage, thereby maintaining reliability under repeated deformation.
Solution Approach 2:
The second conductor layer serves as an intermediary between the resin layer and the first conductor layer, mediating the transmission of mechanical stresses. This intermediate layer with high ductility protects the electrical conductor from direct exposure to bending stresses while maintaining the flexible board's ability to bend for space-efficient applications.
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
This configuration effectively prevents disconnection in conductor layers during both the manufacturing process and repeated deformation, ensuring a reliable and high-productivity flexible board with improved resistance to deformation.
Implementation Method 1
the second metal having a greater ductility than the first metal. Upon bending, the second conductor layer made of the ductile metal effectively absorbs and relieves stress on the conductor layer
Implementation Method 2
The second metal preferably retards or prevents the grain growth of the first metal
Implementation Method 3
A portion of the second metal of the second conductor layer preferably enters a grain boundary of the first metal of the first conductor layer and partially diffuses into crystal grains of the first metal
Implementation Method 4
at least a portion of the second conductor layer includes an alloy of the first metal and the second metal. The alloy may preferably be formed during a process of stacking the conductor layers and the resin layers
Data Source
AI summary
A reliable flexible board prevents disconnection from occurring in a conductor layer in a stacking process or during use of a product that repeatedly causes deformation. The flexible board includes resin layers and conductor layers that are alternately stacked on top of one another, wherein each of the conductor layers includes a first conductor layer made of a first metal and a second conductor layer made of a second metal disposed between one of the resin layers and the first conductor layer, the second metal having a higher ductility than the first metal.