Flexible Multilayer Substrate Skin Layer Joint Plane Positioning
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Solution Overview
Problem
Flexible multilayer substrates experience separation issues at joint planes of via conductors or resin layers when flexed, leading to reliability concerns during repeated bending.
Innovation Solution
Incorporating a skin layer with a harder resin compound on the inner surface and positioning the skin layer joint plane closer to the innermost surface than the central plane, along with tapered via conductors to compress the joint area, reducing the likelihood of separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the flexible multilayer substrate is used in the flexed state or flexed repeatedly during use, then the substrate can be mounted and used in compact or flexible applications, but separation occurs at the joint plane of via conductors or resin layers
Solution Approach 1:
The patent applies local quality by creating a skin layer with different hardness properties than the bulk resin. The skin layer has a hardness of 60-80 Shore D while the bulk resin has a hardness of 40-55 Shore D. This localized difference in mechanical properties allows the joint plane to resist separation during flexing while maintaining overall substrate flexibility.
Solution Approach 2:
The patent changes the physical parameter of hardness by forming a skin layer with higher hardness than the bulk resin through UV irradiation or electron beam irradiation. This parameter change creates a compressed state at the joint plane during flexing, preventing separation while preserving the substrate's ability to bend.
2Reliability
If a skin layer with different hardness is formed on the resin layer, then separation at the joint plane is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The skin layer is formed as a preliminary step before lamination. By pre-forming the skin layer with increased hardness on the resin layers before they are bonded together, the structure is prepared in advance to resist separation at the joint plane, simplifying the overall manufacturing process compared to post-processing methods.
Solution Approach 2:
The patent replaces purely mechanical lamination with a combined photochemical/mechanical approach. UV irradiation or electron beam irradiation is used to modify the resin surface properties, creating a harder skin layer that provides mechanical resistance to separation, thus substituting part of the mechanical lamination function with a photochemical or radiative process.
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 separation at the skin layer joint plane and via conductor joints, maintaining structural integrity during flexing and repeated use.
Implementation Method 1
A skin layer is provided in a vicinity of the first main surface and the skin layer is harder than other portions of the resin layer
Implementation Method 2
the skin layer joint plane is located on a side closer to the innermost surface than a central plane in the thickness direction of the multilayer body. With this configuration, the skin layer joint plane is in a compressed state rather than a stretched state
Implementation Method 3
Each of the via conductors has a tapered shape with a diameter in the first main surface greater than a diameter in the second main surface
Data Source
AI summary
A flexible multilayer substrate includes a multilayer body including a plurality of laminated resin layers. The multilayer body includes an innermost surface, which is a surface on an inner side when the substrate is bent, and an outermost surface, which is a surface on an outer side when the substrate is bent. Each of the plurality of resin layers includes a skin layer on one surface. Lamination of the multilayer body includes a skin layer joint plane at one location at a central portion in the thickness direction, and the skin layer and other surface come in contact with each other at another location along the central portion in the thickness direction. A skin layer joint plane is arranged on a side closer to the innermost surface than a central plane in the thickness direction of the multilayer body.