Carrier Surface Roughness Control for Ultrathin Copper Foil Peeling

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Solution Overview

Problem

The challenge in producing printed wiring boards is the difficulty in peeling the ultrathin copper layer from the carrier due to increased peel strength in laminates formed using copper foils with carriers, which hinders the fabrication process.

Innovation Solution

A copper foil with a carrier is developed, where the surface roughness of the carrier opposite to the ultrathin copper layer is controlled to enhance the peel strength, specifically with a ten point average roughness Rz of 6.0 μm or less, and an arithmetic average roughness Ra of 1.0 μm or less, allowing for effective peeling of the ultrathin copper layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the surface roughness of the carrier is increased to improve adhesion to the resin substrate, then the peel strength between the ultrathin copper layer and the carrier increases, but this makes it difficult to peel the ultrathin copper layer from the carrier

Engineering Contradiction:

Improveadhesion strength between carrier and resin substrateVSAvoidpeelability of ultrathin copper layer from carrier

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The patent applies different surface roughness characteristics to different regions of the carrier. The first surface (contacting resin substrate) has higher roughness for strong adhesion, while the second surface (contacting ultrathin copper layer) has lower roughness for easy peeling. This local differentiation resolves the contradiction by optimizing each surface for its specific function.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The carrier is segmented into two distinct surfaces with different properties. The first surface is designed with roughness Rz≤6.0μm for resin substrate adhesion, while the second surface is designed with roughness Rz≤3.0μm for ultrathin copper layer peeling. This segmentation allows each surface to independently fulfill its required function without interference.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If the foil thickness is reduced to achieve fine pitch requirements, then the conductive pattern precision improves, but the handleability in forming copper-clad laminate deteriorates

Engineering Contradiction:

Improvefine pitch conductive pattern precisionVSAvoidhandleability in forming copper-clad laminate

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The patent introduces a carrier as an intermediary support structure for the ultrathin copper layer (5μm or less). The carrier provides mechanical strength and handleability during the copper-clad laminate formation process, while allowing the ultrathin copper layer to maintain its fine pitch precision. The controlled surface roughness of the carrier enables easy peeling after lamination.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent uses an ultrathin copper layer (5μm or less) that is too thin to handle independently, supported by a flexible carrier. The carrier acts as a temporary substrate that provides the necessary mechanical properties for processing, while the ultrathin copper layer maintains its precision for fine pitch applications. After lamination to the resin substrate, the carrier is peeled off.

Inventive Principle:

Principle #30Flexible shells and thin films

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 solution enables the successful peeling of the ultrathin copper layer from the carrier, improving the handling and fabrication of printed wiring boards by reducing the peel strength and maintaining adequate adhesion to the resin substrate.

Implementation Method 1

the surface roughness of the carrier opposite to the ultrathin copper layer is controlled to enhance the peel strength, specifically with a ten point average roughness Rz of 6.0 μm or less, and an arithmetic average roughness Ra of 1.0 μm or less

Methodology Applied

Scientific EffectSurface roughness control:

Data Source

PatentUS10178775B2Copper foil provided with carrier, laminate, printed wiring board, and method for fabricating printed wiring board

Publication Date: 2019.01.08 JX NIPPON MINING & METALS CORP

AI summary

Provided is a copper foil provided with a carrier which enables, in a laminate produced by laminating a copper foil provided with a carrier on a resin substrate, to peel the ultrathin copper layer from the carrier well. A copper foil provided with a carrier having, in order, a carrier, an intermediate layer, and an ultrathin copper layer, wherein, when the surface of the carrier opposite to the ultrathin copper layer is measured using a laser microscope based on JIS B0601-1994, the ten point average roughness Rz of the surface is 6.0 μm or less.