Printed Wiring Board Hollow Via Structure Against Resin Intrusion
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Solution Overview
Problem
Conventional printed wiring boards face challenges in maintaining a sealed hollow structure for inner vias, as resin flow into holes during the build-up process can be disrupted by heat expansion, leading to structural damage and difficulty in achieving a sealed hollow waveguide space.
Innovation Solution
The printed wiring board design includes a core substrate with a hollow via inner space connected to the outside through pre-formed holes in build-up layers, using resin with low flowability and specific materials to prevent resin intrusion, and employing heat-resistant prepregs to maintain the hollow structure during the build-up process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If resin is used to fill vias during the build-up process, then the resin layer can be formed and layers can be connected, but heat expansion during the build-up process disrupts the sealed hollow structure and causes structural damage
Solution Approach 1:
The via holes are formed and the hollow structure is established before the build-up process begins. The core substrate is prepared with pre-formed via holes that maintain their hollow structure before any heating or resin application occurs, allowing the sealed structure to be created in advance of the thermal build-up process
Solution Approach 2:
The printed wiring board is divided into a core substrate portion and a build-up layer portion. The core substrate contains the hollow via holes, while the build-up layers are formed separately and then combined. This segmentation allows the hollow structure to be preserved in the core substrate while the build-up layers are formed with minimal thermal impact on the via holes
2Ease of manufacture
If conventional build-up process is used, then layers can be formed and connected, but resin flows into via holes and prevents formation of sealed hollow waveguide space
Solution Approach 1:
The via holes are formed and prepared in the core substrate before the build-up process. The hollow structure is established in advance, and then the build-up layers are formed around these pre-existing holes, preventing resin from filling the via holes while maintaining the sealed hollow waveguide space
Solution Approach 2:
The core substrate is designed with specific local properties - the via holes are formed with precise dimensions and positioning to create the hollow waveguide structure. This local quality control ensures that the via holes remain open and sealed appropriately while the surrounding build-up layers are formed with different material properties
Data Source
AI summary
A printed wiring board is provided with: a core substrate corresponding to a stack area in which an interlayer connection conductor constituting an inner via is continuous; and a build-up layer comprising a resin layer stacked on the core substrate and a conductor layer on said resin layer. A via inner space inside the interlayer connection conductor constituting the inner via is hollow, and said via inner space communicates to the outside via a hole section provided in the build-up layer.