Surface Treated Copper Foil Adhesion Transparency Trade-off
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Solution Overview
Problem
Existing copper clad laminates face issues with adhesion strength between the copper foil and resin, leading to disconnection and poor transparency when observed through the resin, particularly in flexible printed wiring boards and electronic components.
Innovation Solution
A surface treated copper foil with a controlled surface color difference ΔE*ab of 40 or more and a specific brightness gradient, achieved through alloy plating and roughening treatments, is laminated with a polyimide substrate to enhance adhesion and visibility, ensuring excellent visibility and alignment during electronic component mounting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If blackening treatment or organic treating agent is applied after plating treatment to improve adhesion, then adhesion strength is improved, but transparency of resin deteriorates
Solution Approach 1:
The patent employs a low-profile copper foil that is sacrificial in nature - it is intentionally designed to be etched away completely after serving its bonding purpose during lamination. The copper foil acts as a temporary bonding agent that provides strong adhesion during manufacturing but is then removed, leaving no residue that would affect transparency. This resolves the contradiction by making the adhesion-enhancing copper foil temporary rather than permanent.
Solution Approach 2:
The patent extracts the copper foil from the final product structure - it is used during the lamination process to ensure strong bonding between the resin and other components, but then completely removed through etching. This extraction eliminates the source of opacity (the copper foil itself) while retaining its beneficial adhesion function during the critical bonding phase.
2Strength
If roughening treatment is applied to copper foil surface to improve adhesion, then adhesion strength is improved, but visibility through resin deteriorates
Solution Approach 1:
The low-profile copper foil with roughened surface is designed as a temporary component that provides mechanical interlocking through surface roughness during lamination, then is completely etched away. The roughness feature serves its adhesion purpose temporarily and is then removed, preventing any lasting impact on visibility.
Solution Approach 2:
The roughened copper foil is extracted from the final structure after serving its bonding function. The etching process completely removes the copper material, taking with it the roughness feature that would otherwise scatter light and reduce visibility, while the adhesion benefit is already realized in the bonded structure.
3Strength
If copper foil is used to ensure flexibility and adhesion, then adhesion strength is improved, but transparency of resin deteriorates
Solution Approach 1:
The copper foil is designed as a consumable bonding agent - it provides the necessary flexibility and adhesion during the lamination process but is then completely removed through etching. This temporary use allows the copper foil to fulfill its mechanical function without permanently compromising the optical properties of the resin.
Solution Approach 2:
The copper foil is extracted from the final product after serving its dual purpose of providing flexibility and adhesion during manufacturing. The complete removal through etching eliminates the source of opacity while the structural benefits of having used copper foil during lamination are already realized.
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 treated copper foil achieves improved adhesion to the resin, maintaining transparency and facilitating accurate alignment and positioning of electronic components, thereby enhancing the manufacturing yield and reliability of printed wiring boards and electronic devices.
Implementation Method 1
forming a copper-cobalt-nickel alloy plating layer by electroplating
Implementation Method 2
forming a cobalt-nickel alloy plating layer after surface roughening treatment of the copper foil surface by plating with a copper-cobalt-nickel alloy
Data Source
AI summary
A surface treated copper foil which is well bonded to a resin and achieves excellent visibility when observed through the resin, and a laminate using the same are provided. A surface treated copper foil comprising at least one surface treated surface with a color difference ΔE*ab of 40 or more based on JIS Z 8730, and a difference between the top average Bt and the bottom average Bb in a brightness curve extending from an end of the copper foil to a portion without the copper foil ΔB (ΔB=Bt−Bb) of 40 or more, after lamination of the surface treated surface to a polyimide having a ΔB (PI) defined as above of 50 or more and 65 or less before being laminated to the copper foil, wherein the brightness curve is obtained from an observation spot versus brightness graph of measurement results of the brightness of the photographed image of the copper foil through the polyimide with a CCD camera for the respective observation spots along the direction perpendicular to the extending direction of the observed copper foil.