Multilayer PCB Manufacturing via Differential Etching
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Solution Overview
Problem
The limitations of etching equipment and processes restrict the development of thick copper multilayer printed circuit boards, particularly in achieving standard line widths and spacings, and affect the fillability of conductive vias due to high aspect ratios, hindering their design and manufacturing for high-power and high-reliability applications.
Innovation Solution
The use of an inner circuit laminated structure with alternating layers of copper and silver, where each metal layer has different etching abilities, allowing for precise etching and reducing the thickness of the board, along with the omission of a core board to enhance electroplating success rates and mechanical support, enabling thinner and lighter designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional etching equipment and processes are used, then manufacturing simplicity is maintained, but line width and line spacing cannot meet fine trace standards
Solution Approach 1:
The patent segments the etching process into multiple stages: first etching the copper layer to form through-holes, then etching the silver layer to form conductive patterns. This segmentation allows each layer to be etched with optimized parameters, achieving fine trace precision that would be impossible with a single etching process.
Solution Approach 2:
The patent applies preliminary action by first forming through-holes in the copper layer before depositing and etching the silver layer. This preliminary structuring enables subsequent precise etching of fine traces in the silver layer, as the copper through-holes already provide the basic conductive pathways.
2Power
If thick copper layers are used for high power applications, then power handling capability is improved, but aspect ratio of conductive vias increases reducing fillability
Solution Approach 1:
The patent uses a composite structure with alternating copper and silver layers. The copper layers provide high power handling capability due to copper's excellent electrical conductivity, while the silver layers provide precise etchability and good via fillability. This composite material approach allows thick conductor layers for high power while maintaining manufacturable via aspect ratios.
Solution Approach 2:
The patent segments the conductor function across multiple thin layers (copper and silver alternating) rather than using a single thick copper layer. This segmentation reduces the effective via depth that needs to be filled, improving fillability while maintaining overall power handling capability through the stacked conductive paths.
3Strength
If multiple thick copper layers are stacked, then mechanical strength and power capability are improved, but board thickness increases adding weight
Solution Approach 1:
The patent replaces portions of the traditional all-copper multilayer structure with silver layers. Silver has adequate mechanical strength and excellent electrical properties. By alternating copper and silver layers, the board achieves required mechanical strength and power capability with reduced overall thickness and weight compared to equivalent all-copper constructions.
Solution Approach 2:
The patent changes the material parameter from pure copper to alternating copper-silver composition. This parameter change allows optimization of the strength-to-weight ratio, as the thinner silver layers provide sufficient structural support while the copper layers provide the primary power handling, achieving lighter weight than traditional thick copper boards.
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 improved line width and spacing standards, increased reliability, and enhanced electroplating success, meeting requirements for large current flow and high power applications while reducing production complexity and weight.
Implementation Method 1
The first type metal layer and the second type metal layer have different etching ability
Implementation Method 2
the thickness of the multi-layer printed circuit board is such that the aspect ratio of the conductive vias is relatively high. The high aspect ratio affects the fillability of substrate in the conductive vias.
Data Source
AI summary
A method for manufacturing such multilayer printed circuit board includes providing a metal laminated structure including a first type metal layer and a second type metal layer, pressing a patterned dry film layer and a protective film layer on two surfaces of the metal laminated structure, the dry film layer exposing the second type metal layer; etching the second type metal layer to form a first conductive circuit layer; etching a first type metal layer to form a second conductive circuit layer, the first conductive circuit layer and the second conductive circuit layer defining an inner circuit laminated structure; removing the dry film layer; and forming a first adding-layer circuit base board and a second adding-layer circuit base board on two surfaces of the inner laminated structure.