PCB Top Metal Layer Formation Without Plating Protrusions
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Solution Overview
Problem
Conventional printed circuit board (PCB) manufacturing methods result in top metal layers with protrusions due to overspreading, affecting reliability and requiring additional processing steps, which can lead to delamination and voids between layers.
Innovation Solution
A flash plating process is used to fill corner portions of the circuit pattern etched during preprocessing, followed by surface processing, forming a top metal layer with a wider width than the second circuit pattern, which minimizes protrusions and enhances structural stability, allowing for the removal of the nickel seed layer and selection between electrolytic and electroless surface processing methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional electroplating and grinding processes are used to form circuit patterns, then circuit patterns can be formed on insulating layers, but the top metal layer develops protrusions that reduce reliability
Solution Approach 1:
A curved surface is formed on the circuit pattern before the top metal layer is deposited. This preliminary shaping prevents the top metal layer from forming protrusions during electroplating, as the curvature directs the plating solution flow and metal deposition evenly across the surface, eliminating the need for subsequent grinding or planarization steps that would otherwise be required to remove protrusions.
2Ease of manufacture
If the top metal layer is formed with gaps between the mask and circuit pattern, then surface processing can be performed, but the top metal layer spreads onto corner portions creating protrusions
Solution Approach 1:
The circuit pattern is given a curved surface configuration before top metal layer formation. This curvature prevents the plating solution from pooling at corners and edges during electroplating, thereby controlling the top metal layer to deposit uniformly within the intended boundaries and preventing unwanted spreading onto corner portions that would create protrusions.
3Manufacturing precision
If additional processing steps are added to remove protrusions, then manufacturing precision improves, but device complexity and production time increase
Solution Approach 1:
The curved surface is formed on the circuit pattern before top metal layer deposition, serving as a preventive measure that eliminates the need for subsequent protrusion removal steps. This preliminary action ensures that the top metal layer forms with the correct dimensions and shape directly during electroplating, simplifying the overall manufacturing process by eliminating grinding, planarization, or re-etching steps.
4Reliability
If the curved surface is formed on the circuit pattern, then top metal layer protrusions are prevented, but additional processing steps are required
Solution Approach 1:
The curved surface formation process is integrated with existing circuit pattern manufacturing steps, such as combining it with the etching or plating process itself. By merging the curvature formation into the existing workflow rather than adding a completely separate step, the method maintains high productivity while achieving the reliability benefits of protrusion-free top metal layers.
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 improves the reliability of the PCB by preventing overspreading failures, reducing product thickness and cost, and enhancing structural stability while suppressing delamination and voids between layers.
Implementation Method 1
a flash plating process is performed to fill corner portions of a circuit pattern
Implementation Method 2
a top metal layer formed on the circuit pattern by electroplating
Data Source
AI summary
A method of manufacturing a printed circuit board includes providing an insulating layer, forming a plating seed layer on the insulating layer, forming a first circuit pattern on the plating seed layer and a second circuit pattern on the first circuit pattern, and forming a top metal layer on the second circuit pattern. The second circuit pattern can be thinner than the first circuit pattern, and the top metal layer can be wider than the second circuit pattern.