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 of the resin after etching, particularly in flexible printed wiring boards and chip-on-flex applications.
Innovation Solution
A surface treated copper foil with controlled surface skewness (Rsk) and roughness (Rz) is developed, allowing for improved adhesion and transparency of the resin after etching, achieved through specific alloy plating and etching processes, ensuring high peel strength and visibility of the resin substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If blackening treatment or organic treating agent is applied after plating treatment to improve adhesiveness, then adhesion strength is improved, but transparency of the resin becomes poor
Solution Approach 1:
The invention changes the surface treatment parameters by controlling the surface roughness (Rz: 0.05 to 1.5 μm) and applying specific plating treatments (Cu-Fe-Ni alloy plating with controlled thickness) to achieve both good adhesion and transparency. The surface skewness (Rsk: -0.35 to 0.53) is also controlled to optimize the balance between adhesion and transparency.
Solution Approach 2:
The invention uses a composite surface treatment structure consisting of multiple plating layers (Cu-Fe-Ni alloy) combined with controlled surface roughness treatment. This composite approach allows the surface to exhibit both high adhesion strength and good transparency properties simultaneously.
2Illumination intensity
If no roughening treatment is performed to maintain surface smoothness, then transparency is maintained, but adhesion strength becomes low and insufficient
Solution Approach 1:
The invention optimizes the surface roughness parameter (Rz: 0.05 to 1.5 μm) and surface skewness (Rsk: -0.35 to 0.53) to achieve the optimal balance between transparency and adhesion. This controlled roughness level provides sufficient mechanical interlocking for adhesion while maintaining optical clarity.
Solution Approach 2:
The invention applies surface treatment selectively to create localized roughness features that enhance adhesion at the copper-resin interface without significantly affecting the overall optical properties of the resin layer.
3Manufacturing precision
If Cu-Co-Ni alloy plating is applied to fine the copper foil surface, then surface uniformity is improved, but transparency of the resin after copper removal becomes insufficient
Solution Approach 1:
The invention changes the plating composition and parameters by using Cu-Fe-Ni alloy instead of Cu-Co-Ni alloy, and controls the plating thickness and surface roughness (Rz: 0.05 to 1.5 μm) to achieve both surface uniformity and transparency. The specific surface skewness range (Rsk: -0.35 to 0.53) is also controlled.
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 surface treated copper foil ensures excellent adhesion to the resin and maintains high transparency after etching, facilitating accurate alignment and mounting of IC chips, thereby enhancing the reliability and yield of electronic components.
Implementation Method 1
a surface treated copper foil which is well bonded to a resin and allows the resin to have excellent transparency after removal of the copper foil by etching
Implementation Method 2
after removal of the copper foil by etching
Data Source
AI summary
A surface treated copper foil which is well bonded to a resin and allows the resin to have excellent transparency after removal of the copper foil by etching, and a laminate using the same are provided. A surface treated copper foil having at least one surface with a skewness Rsk of −0.35 to 0.53, comprising an Sv defined by the following expression (1) of 3.5 or more based on a brightness curve:Sv=(ΔB×0.1)/(t1−t2) (1);wherein the brightness curve is obtained from an observation spot versus brightness graph, and the difference between the top average Bt and the bottom average Bb in the brightness curve extending from an edge of the mark to a portion without the mark is represented by ΔB (ΔB=Bt−Bb); andwherein t1 represents a value pointing the position of the intersection closest to the linear mark among the intersections of the brightness curve and Bt in the observation spot versus brightness graph, and t2 represents a value pointing the position of the intersection closest to the linear mark among the intersections of the brightness curve and 0.1ΔB in the range from the intersections of the brightness curve and Bt to a depth of 0.1ΔB with Bt as reference.