Circuit Board Plating Method for Precision Etching Control
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Solution Overview
Problem
Conventional circuit board manufacturing methods face challenges in controlling circuit clearance expansion and precision due to horizontal etching, which can result in the disappearance of narrower circuit features.
Innovation Solution
A manufacturing method involving a substrate board with through holes, electro-less plating of a first metal layer, followed by a second metal layer, patterning, and an additional third metal layer to reduce horizontal etching and maintain circuit pattern integrity through double plating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isotropic etching is applied to form the circuit pattern, then the etching selectivity is improved, but the circuit clearance expands horizontally and the circuit precision deteriorates
Solution Approach 1:
The patent divides the single etching process into two sequential etching steps. The first etching step removes the photoresist layer and forms the initial circuit pattern, while the second etching step selectively removes the sacrificial metal layer. This segmentation allows each etching step to be optimized independently, with the first step achieving good selectivity and the second step precisely controlling the circuit clearance without excessive horizontal etching.
Solution Approach 2:
The patent introduces a sacrificial metal layer that is deposited and patterned before the final circuit pattern formation. This preliminary structure serves as a template and spacer that defines the exact circuit clearance dimensions. By performing this preliminary action, the subsequent etching process can precisely control the final circuit pattern dimensions without the horizontal expansion problem.
2Ease of manufacture
If a single metal layer is plated to the required thickness, then the plating process is simplified, but the circuit pattern precision deteriorates due to horizontal etching
Solution Approach 1:
The patent segments the metal layer formation into multiple plating steps separated by etching steps. Instead of plating one thick layer, the metal is deposited in thinner layers that are then precisely etched. This segmentation allows better control over the final circuit pattern dimensions while maintaining manufacturing feasibility through standard thin-film deposition and etching processes.
Solution Approach 2:
The patent uses a sacrificial metal layer as an intermediary structure that facilitates precise circuit pattern formation. This intermediary layer is deposited, patterned, and then selectively removed to define the final circuit clearance. The intermediary structure enables precise dimension control that would be difficult to achieve through direct single-step plating and etching.
3Ease of manufacture
If the photoresist layer is used as a mask for etching, then the patterning process is simplified, but the circuit layer with narrow width may disappear due to horizontal etching
Solution Approach 1:
The patent performs preliminary patterning of the sacrificial metal layer before the final circuit pattern etching. This preliminary patterned sacrificial layer acts as a precise template that protects narrow circuit features during the subsequent etching process. By performing this preliminary action, narrow circuit widths are preserved while still using photoresist-based patterning methods.
Solution Approach 2:
The patterned sacrificial metal layer serves as an intermediary mask that provides superior protection compared to photoresist alone. This intermediary structure has better etch resistance and dimensional stability, preventing the horizontal etching that would cause narrow circuit features to disappear. The intermediary mask maintains the simplicity of photoresist patterning while adding a protective layer that preserves narrow circuit widths.
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 method effectively controls circuit clearance expansion and maintains precision by minimizing horizontal etching and filling etched sidewalls, ensuring the desired circuit pattern thickness and preventing pattern disappearance.
Implementation Method 1
a first metal layer is electro-less plated on the surface of the substrate board and the surface of the through holes
Implementation Method 2
a second metal layer is plated on the first metal layer
Implementation Method 3
a third metal layer is plated on the patterned circuit layer
Data Source
AI summary
A manufacturing method of a circuit board is provided. Firstly, a substrate board having a plurality of through holes is provided. Next, a first metal layer is electro-less plated on the surface of the substrate board and the surface of the through holes. Then, a second metal layer is plated on the first metal layer. After that, the second metal layer and the first metal layer are patterned to form a patterned circuit layer. Lastly, a third metal layer is plated on the patterned circuit layer.