Stacked Substrate Wiring via Biasing Member
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Solution Overview
Problem
The existing mounting structures for flexible and non-flexible components in electronic devices are prone to moisture infiltration due to capillary action, which compromises the reliability of mechanical and electrical connections.
Innovation Solution
A stacked configuration of substrates with a wiring substrate joined via conductive adhesive, where the second side surface of the biasing member faces the wiring substrate, creating a larger separation distance to prevent capillary action and enhance the reliability of the connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the flexible wiring board and the non-flexible component are joined closely at the connecting section, then the mechanical connection strength is improved, but moisture infiltration through capillary action increases
Solution Approach 1:
The patent introduces a biasing member positioned between the flexible wiring board and non-flexible component, creating a spatial separation in the vertical dimension. This biasing member with its specific positioning (where the second side surface faces the wiring substrate and is located on the opposite side of the first side surface from the wiring substrate) prevents direct contact while maintaining mechanical stability, thereby blocking capillary action pathways without sacrificing connection strength.
Solution Approach 2:
The biasing member serves as an intermediary element between the flexible wiring board and the non-flexible component. It mediates the connection by providing mechanical support and maintaining appropriate spacing, preventing moisture infiltration through capillary action while ensuring reliable electrical and mechanical connections through the conductive adhesive joining system.
2Reliability
If a biasing member is introduced to prevent capillary action, then moisture infiltration is suppressed, but device complexity increases
Solution Approach 1:
The biasing member performs multiple functions simultaneously: it provides mechanical support to maintain spacing, prevents capillary action by blocking moisture pathways, and facilitates proper alignment of the substrate stack. The conductive adhesive serves dual purposes of electrical connection and mechanical bonding. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.
3Volume of moving object
If the second side surface of the second substrate is positioned close to the wiring substrate, then the device size is reduced, but capillary action occurs causing moisture infiltration
Solution Approach 1:
The patent applies local quality by positioning the second side surface of the second substrate (biasing member) to face the wiring substrate at a specific location, creating a localized spacing region. This localized spacing is sufficient to prevent capillary action in the critical connection areas while maintaining compact overall device dimensions. The spacing is strategically placed where moisture infiltration would most affect connection 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
This configuration effectively suppresses capillary action, ensuring a reliable mechanical and electrical connection by maintaining an appropriate amount of adhesive between the substrates, reducing fatigue and improving the overall reliability of the electronic device.
Implementation Method 1
a wiring substrate disposed to face the first side surface and joined to the first side surface via a first joining member
Implementation Method 2
there is a concern that capillary action might cause moisture to spread in the connecting section through narrow spaces between the flexible wiring board and the non-flexible component
Data Source
AI summary
An electronic device includes a first substrate having a terminal disposed on a first side surface, a second substrate stacked on the first substrate, a third substrate stacked on a opposite side of the second substrate from the first substrate, and a wiring substrate disposed to face the first side surface and joined to the first side surface via a first joining member, wherein a second side surface of the second substrate that faces the wiring substrate is located on an opposite side of the first side surface from the wiring substrate.