PCB Via Partitioning Using Plating Resist to Reduce Stub Length
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Solution Overview
Problem
The existing plated via structures in printed circuit boards (PCBs) often result in signal distortion due to unnecessary conductive material, known as stubs, which interfere with signal integrity and increase bit error rates, particularly at high speeds, and the backdrilling method to remove stubs is costly, inaccurate, and time-consuming.
Innovation Solution
The use of plating resist within the via structure to selectively limit the formation of conductive material, creating electrically isolated segments that only allow necessary conductive material for signal transmission, thereby reducing or eliminating stubs and improving signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If backdrilling is used to remove stubs, then signal integrity is improved, but manufacturing cost and time increase substantially
Solution Approach 1:
The patent applies preliminary action by depositing plating resist material into the via structures before the plating process. This pre-positioned resist material prevents conductive material from forming in stub regions, eliminating the need for subsequent backdrilling operations. The resist is strategically placed to block plating in areas where conductive material is not needed, thereby preventing stub formation at the source rather than requiring corrective action after plating.
Solution Approach 2:
The patent extracts the unnecessary conductive material problem by using plating resist to selectively prevent plating in stub regions. Instead of removing stubs after they are formed (as in backdrilling), the method extracts the unwanted conductive material formation process entirely by blocking it with resist material during the plating stage, thereby eliminating both the stubs and the need for removal operations.
2Manufacturing precision
If plating resist is used to control conductive material formation, then manufacturing precision is improved, but process complexity increases
Solution Approach 1:
The patent uses plating resist material as an intermediary substance that mediates between the plating process and the via structure. The resist material is deposited into specific regions of the via, acting as a temporary barrier that controls where conductive material will form. This intermediary allows precise control over conductive material placement without requiring complex equipment modifications, as the resist can be applied using standard PCB fabrication techniques.
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 allows for increased wiring density and reduced signal degradation by controlling the formation of conductive material within the via structure, providing more efficient and cost-effective PCB production compared to backdrilling, with improved accuracy and reduced risk of damage to the PCB.
Implementation Method 1
The plated via structure is a plated hole within the PCB that acts as a medium for the transmission of an electrical signal
Data Source
AI summary
Systems and methods for simultaneously partitioning a plurality of via structures into electrically isolated portions by using plating resist within a PCB stackup are disclosed. Such via structures are made by selectively depositing plating resist in one or more locations in a sub-composite structure. A plurality of sub-composite structures with plating resist deposited in varying locations are laminated to form a PCB stackup of a desired PCB design. Through-holes are drilled through the PCB stackup through conductive layers, dielectric layers and through the plating resist. Thus, the PCB panel has multiple through-holes that can then be plated simultaneously by placing the PCB panel into a seed bath, followed by immersion in an electroless copper bath. Such partitioned vias increase wiring density and limit stub formation in via structures. Such partitioned vias allow a plurality of electrical signals to traverse each electrically isolated portion without interference from each other.