Copper-Clad Laminate Interface for Fluororesin Heat-Resistant Adhesion

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Solution Overview

Problem

Existing copper-clad laminates using fluororesins for high-frequency printed wiring boards face challenges with low adhesion and heat resistance, particularly at high temperatures, which are critical for applications in harsh environments like aviation and space.

Innovation Solution

A surface-treated copper foil with a zinc-containing layer composed of Zn and a transition element M having a melting point of 1200°C or more is affixed to a fluororesin, with a specific Zn content and Zn/M weight ratio, enhancing adhesion and heat resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a low dielectric constant thermoplastic resin (fluororesin) is used to reduce dielectric loss, then dielectric loss is reduced, but adhesion force to copper foil deteriorates

Engineering Contradiction:
Improvedielectric lossVSAvoidadhesion force
Core Design Contradiction:
Loss of energyVSStrength

Solution Approach 1:

A zinc-containing layer is introduced as an intermediary between the copper foil and fluororesin substrate. This intermediate layer has high chemical activity that enhances adhesion to the fluororesin while the copper foil provides the electrical conductor function, thus resolving the adhesion problem without sacrificing the low dielectric loss property of the fluororesin

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention uses a composite structure consisting of copper foil with a zinc-containing layer applied to its surface. This composite material combines the electrical conductivity of copper with the enhanced adhesion properties of zinc, allowing it to bond effectively to fluororesin while maintaining the low dielectric loss characteristics

Inventive Principle:
Principle #40Composite materials

2Strength

If adhesion between copper foil and fluororesin is improved, then adhesion force is enhanced, but heat resistance deteriorates

Engineering Contradiction:
Improveadhesion forceVSAvoidheat resistance
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The invention optimizes specific parameters of the zinc-containing layer, including zinc content (5-30 mass%), layer thickness (1-10 μm), and composition ratios, to achieve the optimal balance between adhesion force and heat resistance. By precisely controlling these parameters, the copper-clad laminate maintains high adhesion while exhibiting excellent heat resistance with minimal adhesion decrease at elevated temperatures

Inventive Principle:
Principle #35Parameter changes

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 produces a copper-clad laminate with high adhesion and excellent heat resistance, maintaining strong bonding even at high temperatures, suitable for high-frequency applications.

Implementation Method 1

a zinc-containing layer which contains Zn and a transition element M having a melting point of 1200° C. or more, wherein when an interface between the copper foil and the zinc-containing layer is subjected to elemental analysis by X-ray photoelectron spectroscopy (XPS), a content of Zn is 10% by weight or less, and a Zn/M weight ratio, which is a ratio of the content of Zn to the content of the transition element M, is 0.2 or more and 0.6 or less

Methodology Applied
Scientific EffectAdhesion: Adhesive

Implementation Method 2

when an interface between the copper foil and the zinc-containing layer is subjected to elemental analysis by X-ray photoelectron spectroscopy (XPS)

Methodology Applied
Scientific EffectX-ray photoelectron spectroscopy: Photoelectric Effect

Data Source

PatentUS12526929B2Manufacturing methods for copper-clad laminate and printed wiring board
Publication Date: 2026.01.13 MITSUI MINING & SMELTING CO LTD

AI summary

Provided is a method for manufacturing a copper-clad laminate in which a copper foil and a resin are joined together with high heat-resistant adhesion force though a fluororesin, which is a low dielectric constant thermoplastic resin, is used. This method includes providing a surface-treated copper foil including a copper foil and a zinc-containing layer on at least one surface of the copper foil, and affixing a sheet-shaped fluororesin to the zinc-containing layer side of the surface-treated copper foil. The zinc-containing layer is composed of Zn and a transition element M having a melting point of 1200° C. or more. When the interface between the copper foil and the zinc-containing layer is subjected to elemental analysis by XPS, the content of Zn is 10 wt % or less, and the Zn/M weight ratio, the ratio of the content of Zn to the content of the transition element M, is 0.2 to 0.6.