Copper Clad Laminate Adhesion via Oxide Crystal Control
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Solution Overview
Problem
The challenge is to produce a copper clad laminate with high adhesive force between a copper foil and a thermoplastic resin, which has a low dielectric constant, while minimizing conductor loss for high-frequency signal transmission in electronic devices.
Innovation Solution
A method involving a roughened copper foil with fine irregularities composed of acicular crystals containing cupric oxide and cuprous oxide, where the thickness of these oxides is controlled within specific ranges using sequential electrochemical reduction analysis, enhancing adhesion to thermoplastic resins like fluororesin or liquid crystal polymer resins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the surface of copper foil is roughened to improve adhesion to thermoplastic resin, then adhesion strength is improved, but conductor loss increases due to increased surface area
Solution Approach 1:
The invention applies different surface treatments to different regions of the copper foil. The rear surface (bonding surface) is roughened with acicular crystals to enhance adhesion, while the front surface remains smooth to minimize conductor loss. This local differentiation allows simultaneous optimization of both adhesion strength and electrical conductivity.
Solution Approach 2:
The invention changes the surface morphology parameters by controlling the oxidation-reduction treatment to form acicular crystals with specific dimensions (length 0.1-10 μm, width 1-100 nm). By precisely controlling these parameters, the surface provides sufficient adhesion while minimizing the impact on conductor loss through optimized surface area increase.
2Loss of energy
If a thermoplastic resin with low dielectric constant is used to reduce dielectric loss, then dielectric loss is reduced, but adhesion to copper foil deteriorates due to low chemical activity
Solution Approach 1:
The invention creates a localized reactive surface layer on the copper foil through controlled oxidation-reduction treatment. This forms acicular crystals of copper oxide and copper hydroxide on the bonding surface, which provide chemical activity and anchoring points for the thermoplastic resin, compensating for the resin's low chemical activity while maintaining bulk resin properties for low dielectric loss.
Solution Approach 2:
The invention creates a composite surface structure consisting of acicular crystals (copper oxide/copper hydroxide) on the copper foil base metal. This composite structure combines the metallic properties of copper with the oxidized surface layer, providing both electrical conductivity and enhanced chemical reactivity for bonding to low-dielectric thermoplastic resins.
3Strength
If fine irregularities are formed through oxidation-reduction treatment to achieve high adhesion, then adhesion is improved, but manufacturing complexity increases due to multiple treatment steps
Solution Approach 1:
The invention combines the oxidation and reduction treatments into a unified process sequence that forms the desired acicular crystal structure in one integrated workflow. By merging these steps and optimizing their parameters, the process achieves high adhesion without requiring additional separate treatment stages, thereby limiting manufacturing complexity.
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 achieves high adhesion and peel strength between the copper foil and thermoplastic resin, reducing transmission loss and maintaining reliability even in harsh environments, suitable for high-frequency applications.
Implementation Method 1
roughened surfaces with fine irregularities formed through oxidation treatment and then reduction treatment
Implementation Method 2
roughened surfaces with fine irregularities formed through oxidation treatment and then reduction treatment
Data Source
AI summary
There is provided a method of producing a copper clad laminate having a copper foil and a resin bonded at high adhesive force despite the use of a thermoplastic resin having a low dielectric constant. This method includes the steps of: providing a roughened copper foil having at least one roughened surface having fine irregularities composed of acicular crystals containing cupric oxide and cuprous oxide; and bonding a sheet-shaped thermoplastic resin to the roughened surface of the roughened copper foil to provide a copper clad laminate. The roughened surface has a cupric oxide thickness of 1 to 20 nm and a cuprous oxide thickness of 15 to 70 nm, both determined by sequential electrochemical reduction analysis (SERA) at the time of bonding the thermoplastic resin.