Degreasing Treatment of Rolled Copper Foil: Core Process and Key Assurance for Coating and Thermal Lamination Performance

Rolled copper foil is a core material in the electronic circuit industry, and its surface and internal cleanliness directly determine the reliability of downstream processes such as coating and thermal lamination. This article analyzes the mechanism by which degreasing treatment optimizes the performance of rolled copper foil from both production and application perspectives. Using actual data, it demonstrates its adaptability to high-temperature processing scenarios. CIVEN METAL has developed a proprietary deep degreasing process that breaks through industry bottlenecks, providing high-reliability copper foil solutions for high-end electronic manufacturing.

1. The Core of the Degreasing Process: Dual Removal of Surface and Internal Grease

1.1 Residual Oil Issues in the Rolling Process

During the production of rolled copper foil, copper ingots undergo multiple rolling steps to form foil material. To reduce frictional heat and roll wear, lubricants (such as mineral oils and synthetic esters) are used between the rolls and the copper foil surface. However, this process leads to grease retention through two primary pathways:

• Surface adsorption: Under rolling pressure, a micron-scale oil film (0.1-0.5μm thick) adheres to the copper foil surface.
• Internal penetration: During rolling deformation, the copper lattice develops microscopic defects (such as dislocations and voids), allowing grease molecules (C12-C18 hydrocarbon chains) to penetrate the foil via capillary action, reaching depths of 1-3μm.

1.2 Limitations of Traditional Cleaning Methods

Conventional surface cleaning methods (e.g., alkaline washing, alcohol wiping) remove only surface oil films, achieving a removal rate of about 70-85%, but are ineffective against internally absorbed grease. Experimental data show that without deep degreasing, internal grease re-emerges on the surface after 30 minutes at 150°C, with a re-deposition rate of 0.8-1.2g/m², causing “secondary contamination.”

1.3 Technological Breakthroughs in Deep Degreasing

CIVEN METAL employs a “chemical extraction + ultrasonic activation” composite process:

1. Chemical extraction: A custom chelating agent (pH 9.5-10.5) decomposes long-chain grease molecules, forming water-soluble complexes.
2. Ultrasonic assistance: 40kHz high-frequency ultrasound generates cavitation effects, breaking the binding force between internal grease and the copper lattice, enhancing grease dissolution efficiency.
3. Vacuum drying: Rapid dehydration at -0.08MPa negative pressure prevents oxidation.

This process reduces grease residue to ≤5mg/m² (meeting IPC-4562 standards of ≤15mg/m²), achieving >99% removal efficiency for internally absorbed grease.

2. Direct Impact of Degreasing Treatment on Coating and Thermal Lamination Processes

2.1 Adhesion Enhancement in Coating Applications

Coating materials (such as PI adhesives and photoresists) must form molecular-level bonds with copper foil. Residual grease leads to the following issues:

• Reduced interfacial energy: The hydrophobicity of grease increases the contact angle of coating solutions from 15° to 45°, hindering wetting.
• Inhibited chemical bonding: The grease layer blocks hydroxyl (-OH) groups on the copper surface, preventing reactions with resin active groups.

Performance Comparison of Degreased vs. Regular Copper Foil:

2.2 Enhanced Reliability in Thermal Lamination

During high-temperature lamination (180-220°C), residual grease in regular copper foil leads to multiple failures:

• Bubble formation: Vaporized grease creates 10-50μm bubbles (density >50/cm²).
• Interlayer delamination: Grease reduces van der Waals forces between epoxy resin and copper foil, decreasing peel strength by 30-40%.
• Dielectric loss: Free grease causes dielectric constant fluctuations (Dk variation >0.2).

After 1000 hours of 85°C/85% RH aging, CIVEN METAL Copper Foil exhibits:

• Bubble density: <5/cm² (industry average >30/cm²).
• Peel strength: Maintains 1.6N/cm (initial value 1.8N/cm, degradation rate only 11%).
• Dielectric stability: Dk variation ≤0.05, meeting 5G millimeter-wave frequency requirements.

3. Industry Status and CIVEN METAL’s Benchmark Position

3.1 Industry Challenges: Cost-Driven Process Simplification

Over 90% of rolled copper foil manufacturers simplify processing to cut costs, following a basic workflow:

Rolling → Water Wash (Na₂CO₃ solution) → Drying → Winding

This method only removes surface grease, with post-wash surface resistivity fluctuations of ±15% (CIVEN METAL’s process maintains within ±3%).

3.2 CIVEN METAL’s “Zero-Defect” Quality Control System

• Online monitoring: X-ray fluorescence (XRF) analysis for real-time detection of surface residual elements (S, Cl, etc.).
• Accelerated aging tests: Simulating extreme 200°C/24h conditions to ensure zero grease re-emergence.
• Full-process traceability: Each roll includes a QR code linking to 32 key process parameters (e.g., degreasing temperature, ultrasonic power).

4. Conclusion: Degreasing Treatment—The Foundation of High-End Electronics Manufacturing

Deep degreasing treatment of rolled copper foil is not just a process upgrade but a forward-thinking adaptation to future applications. CIVEN METAL’s breakthrough technology enhances copper foil cleanliness to an atomic level, providing material-level assurance for high-density interconnects (HDI), automotive flexible circuits, and other high-end fields.

In the 5G and AIoT era, only companies mastering core cleaning technologies can drive future innovations in the electronic copper foil industry.

(Data Source: CIVEN METAL Technical White Paper V3.2/2023, IPC-4562A-2020 Standard)

Author: Wu Xiaowei (Rolled Copper Foil Technical Engineer, 15 Years of Industry Experience)
Copyright Statement: Data and conclusions in this article are based on CIVEN METAL laboratory test results. Unauthorized reproduction is prohibited.