Stub-Less PCB Via Plating for High-Frequency Noise Reduction
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Solution Overview
Problem
Printed circuit boards (PCBs) face issues with unwanted metal stubs in vias, which generate noise under high-frequency applications, necessitating effective removal methods to improve signal transmission and reduce interference.
Innovation Solution
A method involving drilling through-holes in PCBs, depositing carbon-based materials, and back drilling to form blind vias, followed by selective plating of conductive materials to create stub-less vias, utilizing a specialized drilling tool with a non-conductive core and conductive cutting portions to accurately stop at internal traces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional drilling and plating methods are used to create vias in PCBs, then via formation is achieved, but unwanted metal stubs remain in the vias causing noise interference
Solution Approach 1:
The via formation process is segmented into multiple steps: initial via drilling, back-drilling to remove stubs, depositing carbon-based material, and selective plating. This segmentation allows removal of unwanted metal stubs while maintaining necessary conductive pathways, directly addressing the noise interference problem.
Solution Approach 2:
Different regions of the via receive different treatments: the main via body receives conductive plating for signal transmission, while the blind via portions (stubs) are kept non-conductive by applying carbon-based material and selective plating. This local differentiation eliminates noise from stubs while maintaining functionality.
2Object-affected harmful factors
If back drilling is performed to remove stubs, then noise interference is reduced, but additional process steps and complexity are introduced
Solution Approach 1:
Carbon-based material is deposited on the inner wall of the via before back-drilling and plating operations. This preliminary action creates a non-conductive barrier that prevents conductive material from adhering to stub regions, simplifying the subsequent selective plating process and reducing overall complexity.
Solution Approach 2:
The carbon-based material acts as an intermediary layer between the via wall and conductive plating material. It mediates the selective adhesion process, allowing conductive material to plate only on desired surfaces while preventing plating on stub regions, thereby simplifying the manufacturing process.
3Reliability
If selective plating is used to create stub-less vias, then signal transmission quality is improved, but process time and productivity are reduced
Solution Approach 1:
The carbon-based material is deposited in advance to define the adhesion pattern for subsequent plating operations. This preliminary action enables rapid selective plating without requiring complex real-time control, improving manufacturing speed while maintaining signal transmission quality.
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
The method effectively removes stubs, reducing noise interference and enhancing high-frequency signal transmission by creating stub-less vias without conductive material adherence in blind vias, thus improving PCB performance.
Implementation Method 1
depositing a carbon-based material over an inner wall of the through-hole
Implementation Method 2
selectively plating a conductive material over the carbon-based material
Implementation Method 3
vapor etching to remove the first conductive material from the inner wall of the through-hole
Data Source
AI summary
A method is provided for modifying a via from a PCB including a plurality of subassemblies comprising a plurality of layers. The method may include drilling a via of the PCB to form a through-hole to remove an unwanted material in the via of the PCB. The method may also include depositing a carbon-based material over an inner wall of the through-hole. The method may further include back drilling a first portion of the through-hole by a drill from the top of the PCB to form a first blind via. The method may also include selectively plating a conductive material over the carbon-based material to form a plated through-hole.