Printed Wiring Board Thermal Stress Mitigation via Filled Vias
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Solution Overview
Problem
Hybrid structure printed wiring boards manufactured by integral molding face issues with stress concentration and corner cracking due to differences in thermal expansion coefficients between insulating materials, leading to degraded through-hole connection reliability.
Innovation Solution
A printed wiring board design featuring a core layer, first and second buildup layers with different resins, and filled vias around the through hole circumference to mitigate thermal expansion stress, where the second resin has a greater thermal expansion coefficient and is supported by conductive filled vias to reduce stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If integral molding is used to manufacture hybrid structure substrates, then manufacturing complexity is reduced, but stress concentration and corner cracking occur due to different thermal expansion coefficients between insulating materials
Solution Approach 1:
The patent applies local quality by introducing filled vias specifically at the corner regions where stress concentration occurs. These filled vias are strategically positioned to provide localized reinforcement only where needed, rather than uniformly throughout the entire structure. This localized approach addresses the corner cracking issue while maintaining the overall simplicity of the integral molding process.
Solution Approach 2:
The patent employs composite materials by combining different insulating materials with different thermal expansion coefficients in a single substrate structure. The core layer uses a first insulating material while the buildup layers use a second insulating material, creating a composite structure that can accommodate different thermal expansion characteristics. This is achieved through integral molding with proper material selection and layer configuration.
2Adaptability or versatility
If different insulating materials with different thermal expansion coefficients are used in hybrid structure, then functional performance is improved, but corner cracks occur during cooling/heating cycles due to stress concentration
Solution Approach 1:
The patent applies local quality by introducing filled vias specifically at the corner regions where stress concentration occurs. These filled vias are strategically positioned to provide localized reinforcement only where needed, rather than uniformly throughout the entire structure. This localized approach addresses the corner cracking issue while maintaining the overall simplicity of the integral molding process.
Solution Approach 2:
The patent implements beforehand cushioning by pre-filling vias at corner positions before thermal cycling occurs. These filled vias act as stress relief structures that are already in place to cushion and distribute thermal expansion stresses, preventing crack initiation and propagation during subsequent cooling/heating cycles.
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 significantly reduces the likelihood of corner cracking and maintains reliable through-hole connections even under high-temperature cycling, with minimal resistance change and no disconnection, enhancing the board's thermal expansion management.
Implementation Method 1
the individual insulating materials behave differently during a cooling/heating cycle due to, for example, a difference in thermal expansion coefficient between the insulating materials
Data Source
AI summary
A printed wiring board in the present disclosure includes a core layer, a first buildup layer, a second buildup layer, and a through hole. The core layer has a conductor circuit located on a surface of an insulator. The first buildup layer containing a first resin is laminated on a surface of the core layer. The second buildup layer containing a second resin is laminated on a surface of the first buildup layer. The through hole extends through the core layer, the first buildup layer, and the second buildup layer. The first resin and the second resin are different from each other. The second buildup layer includes a plurality of filled vias filled with a conductor which are located around a circumference of an opening of the through hole.