Copper Foil Sdr and Sq Control for Polyvinyl Acetal Adhesion
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Solution Overview
Problem
The challenge lies in achieving strong adhesion between a copper foil and a polyvinyl acetal resin film, which is thermoplastic and has low reactivity, necessitating low temperature and low pressure lamination, making it difficult to ensure effective bonding.
Innovation Solution
Control the developed interfacial area ratio (Sdr) and root mean square height (Sq) of the copper foil surface within specific ranges to enhance adhesion, using surface treatments like roughening, allowing polyvinyl acetal resin to infiltrate and bond effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If low temperature and low pressure lamination is used for polyvinyl acetal resin, then the resin maintains its thermoplastic properties and light transmission, but adhesion between copper foil and resin film deteriorates
Solution Approach 1:
The invention changes the surface parameters of the copper foil by controlling the developed interfacial area ratio (Sdr) to 0.50-9.00% and root mean square height (Sq) to 0.010-0.200 μm. This surface modification enables the copper foil to achieve adequate adhesion with polyvinyl acetal resin under low temperature (180°C or less) and low pressure (0.6 MPa or less) lamination conditions, resolving the contradiction between maintaining thermoplastic properties and achieving strong adhesion.
2Strength
If copper foil surface is roughened to increase adhesion, then bonding strength improves, but surface flatness deteriorates
Solution Approach 1:
The invention applies local quality modification by creating a controlled surface roughness only at the interface between copper foil and resin film. The Sdr and Sq parameters are precisely controlled to provide adequate surface area for adhesion while maintaining overall surface flatness suitable for lamination, thus resolving the contradiction between adhesion strength and surface flatness.
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 method results in a laminate with improved adhesion between the copper foil and resin film, even under low temperature and low pressure conditions, ensuring effective bonding and performance.
Implementation Method 1
a polyvinyl acetal resin results in low reactivity with a copper foil, and it is difficult to ensure adhesion between the copper foil and the resin film
Data Source
AI summary
Provided is a method for manufacturing a laminate that is excellent in adhesion between a copper foil and a resin film while using a polyvinyl acetal resin having low reactivity with the copper foil. This method includes the steps of providing a copper foil having a treated surface having a developed interfacial area ratio Sdr of 0.50% or more and 9.00% or less and a root mean square height Sq of 0.010 µm or more and 0.200 µm or less on at least one side, and attaching or forming a polyvinyl acetal resin film on the treated surface of the copper foil to form a laminate. The Sdr and Sq are values measured in accordance with ISO 25178 under conditions in which a cutoff wavelength of an S-filter is 0.55 µm, and a cutoff wavelength of an L-filter is 10 µm.