Flexible Printed Circuit Board With Elastic Conductive Wiring
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Solution Overview
Problem
Flexible printed circuit boards face stress concentration issues due to the rigidity of semiconductor elements, leading to potential conduction failures and damage at bonding parts, and existing solutions either have strong adhesive strength that can break under stress or fail to completely eliminate load on mounting regions.
Innovation Solution
A printed circuit board design featuring a flexible insulative substrate with through-holes and conductive members connecting element terminals to wiring, formed from conductive polymer or elastic conductive paste, which disperses stress and maintains connectivity during deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible printed wiring board is used, then the board can be deformed and adapted to narrow spaces, but stress concentrates on bonding parts with terminals of semiconductor devices, causing damage and conduction failure
Solution Approach 1:
The patent divides the bonding structure into multiple segments: the flexible printed wiring board, the semiconductor device, the conductive adhesive, and the resin sealant. This segmentation allows each component to perform its specific function - the flexible board provides adaptability while the segmented bonding structure distributes stress across multiple interfaces rather than concentrating it at single bonding points
Solution Approach 2:
The patent employs composite materials including the conductive adhesive that combines bonding and conductive functions, and the resin sealant that provides both mechanical support and stress distribution. These composite materials enable the bonding structure to simultaneously achieve electrical connectivity, mechanical strength, and stress distribution, resolving the contradiction between flexibility and bonding integrity
2Strength
If conductive adhesive with rigid bonding strength is used, then bonding reliability improves, but the adhesive may break under stress concentration from board deformation
Solution Approach 1:
The patent changes the physical and chemical parameters of the conductive adhesive, specifically its viscosity, conductivity, and bonding strength characteristics. By optimizing these parameters, the adhesive achieves sufficient bonding strength while maintaining flexibility to accommodate board deformation without breaking, thus resolving the contradiction between strong bonding and stress resistance
Solution Approach 2:
The conductive adhesive acts as an intermediary material between the flexible printed wiring board and the semiconductor device. This intermediary layer absorbs and distributes stress, preventing direct stress transmission that would cause rigid bonding failure, while still maintaining strong electrical and mechanical connection
3Reliability
If holes are bored in the printed wiring board to avoid stress concentration, then mounting region reliability improves, but the board structure becomes more complex and manufacturing more difficult
Solution Approach 1:
The patent applies local quality by creating a resin sealant structure that specifically targets and protects the mounting region without requiring global structural modifications. The resin is selectively applied to surround and support the semiconductor device, providing localized stress distribution and protection only where needed, thus avoiding the complexity of bored holes while maintaining mounting region reliability
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 provides a highly reliable printed circuit board with enhanced flexibility and elasticity, effectively dispersing stress and maintaining connection between semiconductor devices and wiring even under deformation, preventing conduction failures.
Implementation Method 1
The insulative substrate has elasticity in which an elongation percentage of the insulative substrate is 20% or more
Implementation Method 2
The conductive members filled in the through-holes connect the element terminals and the wiring
Implementation Method 3
The wiring is formed from a conductive polymer or an elastic conductive paste in which conductive particles are mixed into a resin material
Data Source
AI summary
A printed circuit board includes a printed wiring board including an insulative substrate having a first surface and a second surface opposite to the first surface, and wiring provided on the second surface of the insulative substrate to face the through-holes. The insulative substrate has flexibility and through-holes passing through the insulative substrate from the first surface to the second surface. A semiconductor element is mounted on the first surface of the insulative substrate of the printed wiring board and has element terminals interposed between the printed wiring board and the semiconductor element. Conductive members filled in the through-holes connect the element terminals and the wiring. The insulative substrate has elasticity in which an elongation percentage of the insulative substrate is 20% or more. The wiring is formed from a conductive polymer or an elastic conductive paste in which conductive particles are mixed into a resin material.