Wiring Board Inner Metal Layer Thermal Stress Reduction
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Solution Overview
Problem
Thinner wiring boards for electronic devices are prone to deformation or warping due to thermal stress caused by differences in coefficients of thermal expansion between the insulating substrate and mount/terminal electrodes, leading to connection faults over time.
Innovation Solution
A wiring board design featuring a rectangular insulating substrate with mount and terminal electrodes arranged on opposing sides and an inner metal layer extending perpendicular to these sides, reducing unidirectional thermal stress and preventing deformation or warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the wiring board is made thinner to reduce device size, then the device size is reduced, but the wiring board becomes more prone to deformation and warping under thermal stress
Solution Approach 1:
The invention introduces an inner metal layer that extends in the thickness direction (third dimension) of the insulating substrate. This vertical extension provides additional structural support and thermal expansion compensation in the Z-direction, allowing the wiring board to maintain stability while keeping the overall device footprint small.
Solution Approach 2:
The invention uses a composite structure combining the insulating substrate with an inner metal layer embedded within it. This composite design leverages the complementary properties of insulating materials (electrical insulation, thermal isolation) and metal materials (mechanical strength, thermal expansion matching) to create a wiring board that is both thin and stable under thermal stress.
2Productivity
If the wiring board is made thinner to improve integration, then integration density is improved, but connection reliability deteriorates due to increased susceptibility to thermal stress
Solution Approach 1:
By extending the inner metal layer in the thickness direction, the invention creates a three-dimensional stress distribution pattern that disperses thermal stresses away from the critical connection interfaces. This dimensional approach maintains thin profile while enhancing connection reliability through improved stress management.
Solution Approach 2:
The inner metal layer is strategically positioned and configured within the insulating substrate to provide localized reinforcement at critical stress points. This localized quality enhancement ensures connection reliability is improved where most needed, without requiring the entire wiring board to be thicker.
3Ease of manufacture
If conventional wiring board structure is used, then manufacturing is simpler, but thermal stress concentration occurs causing deformation over time
Solution Approach 1:
The invention segments the wiring board structure into distinct functional layers: the insulating substrate layer and the embedded inner metal layer. This segmentation allows each layer to be optimized for its specific function while maintaining relative manufacturing simplicity through established multi-layer fabrication techniques.
Solution Approach 2:
The inner metal layer acts as an intermediary element between the mount electrodes and terminal electrodes, mediating the thermal expansion differences between these components and the insulating substrate. This intermediary structure prevents direct stress transmission that would cause deformation, while being integrated using standard manufacturing processes.
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 design enhances the reliability of the wiring board by maintaining better connections to electronic components and module substrates, ensuring long-term high reliability and stability under thermal stress.
Implementation Method 1
thermal stress resulting from differences in coefficients of thermal expansion between the insulating substrate and the mount electrode and between the insulating substrate and the terminal electrode
Data Source
AI summary
A wiring board includes an insulating substrate that is rectangular in a plan view, a plurality of mount electrodes arranged to face each other on a first main surface of the insulating substrate along a pair of opposing sides of the insulating substrate in a plan view, a plurality of terminal electrodes arranged to face each other on a second main surface of the insulating substrate along the pair of opposing sides of the insulating substrate in a perspective plan view, and an inner metal layer arranged inside the insulating substrate and extending in a direction perpendicular to the pair of opposing sides of the insulating substrate in a perspective plan view.