Adhesive-Attached Metal Substrate for Low-Loss High-Frequency Lamination

Solution Overview

Problem

In high frequency transmission, the skin effect causes increased transmission loss due to non-smooth metal surfaces, leading to reduced adhesion between resin and metal substrates, resulting in circuit peeling.

Innovation Solution

An adhesive-attached metal substrate with a copper foil surface roughness of 1.5 µm or less, using an adhesive resin composition containing polyimide resin, maleimide compound, and a radical initiator, with specific mass ratios and thicknesses, laminated with prepregs to enhance adhesion and reduce dielectric loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the surface roughness of metal foil is decreased to reduce transmission loss, then transmission characteristics are improved, but adhesion between resin substrate and metal foil decreases

Engineering Contradiction:

Improvetransmission lossVSAvoidadhesion strength

Core Design Contradiction:

Loss of energyVSStrength

Solution Approach 1:

The invention changes the chemical composition parameters of the adhesive resin layer by specifying a mass ratio of polyimide resin to maleimide compound between 10:1 to 3:2, and controlling radical initiator content between 1-25 parts by mass per 100 parts by mass of maleimide compound. This chemical parameter optimization enables the adhesive to effectively bond smooth metal surfaces with reduced roughness (Rzjis ≤ 1.5 μm) while maintaining strong adhesion.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a composite adhesive resin system combining polyimide resin and maleimide compound in specific proportions, creating a composite material that simultaneously provides both adhesion to smooth metal surfaces and low dielectric loss for high-frequency transmission. This composite approach allows the adhesive layer to fulfill multiple conflicting requirements.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a metal foil with small surface roughness is used to reduce skin effect loss, then transmission characteristics are improved, but circuit peeling occurs due to insufficient adhesion

Engineering Contradiction:

Improvetransmission characteristicsVSAvoidadhesive strength

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The invention optimizes the chemical composition parameters of the adhesive resin layer by specifying a mass ratio of polyimide resin to maleimide compound between 10:1 to 3:2, and controlling radical initiator content between 1-25 parts by mass per 100 parts by mass of maleimide compound. This chemical parameter optimization enables the adhesive to effectively bond smooth metal surfaces with reduced roughness (Rzjis ≤ 1.5 μm) while maintaining strong adhesion.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a composite adhesive resin system combining polyimide resin and maleimide compound in specific proportions, creating a composite material that simultaneously provides both adhesion to smooth metal surfaces and low dielectric loss for high-frequency transmission. This composite approach allows the adhesive layer to fulfill multiple conflicting requirements.

Inventive Principle:

Principle #40Composite materials

3Strength

If the adhesive resin layer thickness is increased to improve adhesion, then adhesive strength is improved, but transmission loss increases

Engineering Contradiction:

Improveadhesive strengthVSAvoidtransmission loss

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

The invention optimizes the chemical composition parameters of the adhesive resin layer by specifying a mass ratio of polyimide resin to maleimide compound between 10:1 to 3:2, and controlling radical initiator content between 1-25 parts by mass per 100 parts by mass of maleimide compound. This chemical parameter optimization enables the adhesive to effectively bond smooth metal surfaces with reduced roughness (Rzjis ≤ 1.5 μm) while maintaining strong adhesion.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a composite adhesive resin system combining polyimide resin and maleimide compound in specific proportions, creating a composite material that simultaneously provides both adhesion to smooth metal surfaces and low dielectric loss for high-frequency transmission. This composite approach allows the adhesive layer to fulfill multiple conflicting requirements.

Inventive Principle:

Principle #40Composite materials

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 solution provides excellent transmission characteristics and sufficient adhesive strength between resin and metal layers, reducing transmission loss and preventing circuit peeling.

Implementation Method 1

the adhesive resin composition contains a polyimide resin (A), a maleimide compound (B), and a radical initiator

Methodology Applied

Scientific EffectPolymerization: Photopolymerisation

Implementation Method 2

a mass ratio between the polyimide resin (A) and the maleimide compound (B) is 10:1 to 3:2, and the content of the radical initiator, with respect to 100 parts by mass of the maleimide compound (B), is equal to or more than 1 part by mass and less than 25 parts by mass

Methodology Applied

Scientific EffectCrosslinking:

Implementation Method 3

As the surface roughness of a metal foil decreases, an anchor effect is less likely to be obtained, and adhesion between a resin substrate and a metal foil decreases

Methodology Applied

Scientific EffectAnchor effect:

Implementation Method 4

In high frequency transmission, a current tends to flow only on the surface of metal wiring as the frequency band becomes higher. Therefore, if the shape of the surface is not smooth, a transmission loss increases. This is a known phenomenon called a 'skin effect'

Methodology Applied

Scientific EffectSkin effect: Skin Effect

Data Source

PatentEP4691762A1Adhesive-attached metal substrate, and laminate

Publication Date: 2026.02.11 ZACROS CORP

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Figure 3

AI summary

The present invention relates to an adhesive-attached metal substrate and a laminate, which are excellent in transmission characteristics and can sufficiently ensure adhesive strength between a resin substrate and a metal layer. More specifically, the present invention relates to an adhesive-attached metal substrate including a metal layer and an adhesive resin layer formed of an adhesive resin composition, in which the adhesive resin composition contains a polyimide resin (A), a maleimide compound (B), and a radical initiator, a mass ratio between the polyimide resin (A) and the maleimide compound (B) is 10:1 to 3:2, and the content of the radical initiator, with respect to 100 parts by mass of the maleimide compound (B), is equal to or more than 1 part by mass and less than 25 parts by mass, and a laminate including the adhesive-attached metal substrate.