Fine-Via Circuit Board Structure for Low-Loss 5G Signal Routing
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Solution Overview
Problem
Existing circuit boards face challenges in forming fine via holes with minimal size and uniformity, leading to increased signal transmission loss and processing issues due to the use of resin coated copper (RCC) with reduced filler content, which limits via hole refinement and adhesion between insulating layers and circuit patterns.
Innovation Solution
The circuit board design incorporates an insulating layer made of RCC or prepreg with controlled via dimensions, minimizing the difference between maximum and minimum widths by selectively removing the copper foil layer and using laser processing to form precise via holes, ensuring low dielectric constant and improved adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If filler content is reduced in RCC to achieve low dielectric constant, then dielectric constant decreases, but via hole formation precision deteriorates
Solution Approach 1:
The patent segments the via hole formation process into two distinct stages: first forming a via hole through the insulating layer, then separately forming a plug within the via hole. This segmentation allows each stage to be optimized independently, enabling precise via hole formation even in low-filler RCC materials that would otherwise be difficult to process.
Solution Approach 2:
The patent performs preliminary action by forming the via hole structure before filling it with conductive material. The via hole is precisely formed in the insulating layer first, then a plug is subsequently formed within it. This preliminary formation of the via hole structure enables precise dimensional control that would be difficult to achieve if attempting to form the complete via structure in one step with low-filler materials.
2Length of moving object
If via hole size is reduced to achieve fine via, then via hole dimension decreases, but signal transmission loss increases
Solution Approach 1:
The patent applies local quality by creating a plug structure with different material properties than the surrounding via hole wall. The plug material is specifically selected to provide low signal transmission loss, while the via hole structure provides precise dimensional control. This local differentiation of material properties allows the via to be both small in size and low in signal loss.
Solution Approach 2:
The patent uses composite materials by combining different materials for the via hole structure and the plug. The insulating layer material (RCC or prepreg) provides mechanical support and insulation, while the plug material (conductive or non-conductive) provides either electrical connection or additional insulation. This composite approach allows optimization of each component for its specific function, enabling small via size with minimal signal loss.
3Manufacturing precision
If via hole dimension is minimized to achieve fine via, then via hole width decreases, but adhesion between insulating layer and circuit pattern deteriorates
Solution Approach 1:
The patent introduces a plug as an intermediary element within the via hole structure. This plug serves as a mediator that can provide adhesion between the insulating layer and the circuit pattern while maintaining the minimized via hole dimensions. The plug material is specifically selected to provide appropriate adhesion properties, decoupling the via hole size from the adhesion requirement.
4Stability of the object's composition
If difference between maximum and minimum via width is minimized to achieve uniform via, then width variation decreases, but manufacturing complexity increases
Solution Approach 1:
The patent segments the via formation into two independent steps: via hole formation and plug formation. This segmentation allows each step to be optimized for its specific purpose - the via hole formation focuses on achieving uniform width, while the plug formation focuses on filling or partially filling the via hole. This separation of functions reduces the overall manufacturing complexity compared to attempting to achieve both uniformity and precise filling in a single step.
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 approach enables the formation of small vias with reduced signal loss and improved reliability, allowing for high-frequency signal transmission suitable for 5G applications while reducing processing costs and maintaining structural integrity.
Implementation Method 1
using laser processing to form precise via holes
Data Source
AI summary
A circuit board according to an embodiment includes an insulating layer, a first circuit pattern layer disposed on the insulating layer; a second circuit pattern layer disposed below the insulating layer; and a via passing through the insulating layer and connecting the first circuit pattern layer and the second circuit pattern layer, wherein the via has a first width at an upper surface and a second width less than the first width at a first region between the upper surface and a lower surface, wherein the first region is a region with a minimum width among all regions of the via, and wherein the second width satisfies a range of 70% to 99% of the first width.