Adhesiveless Copper Clad Laminates for Narrow-Pitch PCBs
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Solution Overview
Problem
Conventional adhesive copper clad laminates face limitations in manufacturing narrow-pitched flexible printed circuit boards due to side etching issues, leading to increased manufacturing costs and reduced adhesive strength, especially when using thin copper foils which are difficult to handle and prone to defects.
Innovation Solution
Adhesiveless copper clad laminates with a nickel alloy base metal layer, a thin copper layer formed by dry plating, and a copper plating film containing 10-150 mass ppm sulfur, allowing for improved microfabrication and reduced undercut during semi-additive processing, enhancing adhesion and preventing exfoliation of microfabricated wiring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If adhesive copper clad laminates are used to manufacture narrow-pitched flexible printed circuit boards, then the wiring pitch can be reduced, but side etching occurs causing increased manufacturing complexity and reduced adhesive strength
Solution Approach 1:
The patent removes the adhesive layer from the copper clad laminate structure, extracting the problematic adhesive component that causes both the bonding issues and the need for complex manufacturing processes. This results in an adhesiveless copper clad laminate that eliminates the technical contradictions associated with adhesive-based systems.
Solution Approach 2:
The patent changes the fundamental parameter of adhesion by transitioning from an adhesive-based bonding system to an adhesiveless system. This parameter change resolves the contradictions by eliminating the adhesive layer that causes manufacturing complexity while maintaining the ability to achieve narrow wiring pitches through direct copper deposition on the insulating film.
2Length of moving object
If thin copper foil is used to reduce side etching, then wiring pitch can be narrowed, but handling ability and stiffness deteriorate
Solution Approach 1:
The patent changes the structural parameter by eliminating the adhesive layer and using a thin base metal layer combined with copper plating. This allows the use of thinner copper equivalents without compromising handling ability, as the adhesiveless structure provides inherent stability while enabling narrow wiring pitches through controlled copper deposition.
3Ease of manufacture
If adhesive copper clad laminates are used, then manufacturing cost is reduced, but adhesive strength and resistance to exfoliation are insufficient
Solution Approach 1:
The patent extracts and removes the adhesive layer from the copper clad laminate structure. This elimination of the adhesive component resolves the contradiction by preventing the exfoliation and bonding failures that occur with conventional adhesive-based systems, while maintaining cost-effectiveness through a simplified structure that requires fewer materials and processing steps.
4Device complexity
If conventional copper clad laminates are used for microfabrication, then manufacturing process is simple, but resist defects increase and microfabrication precision deteriorates
Solution Approach 1:
The patent removes the adhesive layer that interferes with microfabrication processes. This extraction eliminates the source of resist defects and bonding issues that plague conventional adhesive-based copper clad laminates, enabling precise microfabrication while maintaining process simplicity through the adhesiveless structure.
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 solution enables the production of flexible printed circuit boards with improved adhesion, reduced resist defects, and efficient microfabrication, achieving a significant reduction in undercut and maintaining high adhesive strength even with narrow wiring pitches.
Implementation Method 1
a copper coating layer for serving as a conductor layer formed directly on an insulating film by dry plating or wet plating without using an adhesive in between
Implementation Method 2
a copper plating film formed on a front surface of the thin copper layer by electroplating
Data Source
AI summary
Adhesiveless copper clad laminates obtained by metallizing excellent in wiring microfabrication ability in processing by semi-additive method, and a printed circuit board using the adhesiveless copper clad laminates excellent in wiring microfabrication ability as a base material are provided. The adhesiveless copper clad laminates include a base metal layer made of an alloy containing nickel and formed on at least one surface of an insulating film without using an adhesive in between, a thin copper layer formed on a front surface of the base metal layer by dry plating, and a copper plating film formed on a front surface of the thin copper layer by electroplating. The copper plating film contains 10 mass ppm to 150 mass ppm of sulfur in a depth range of at least 0.4 μm from the front surface of the copper plating film in a direction toward the insulating film.