Resin Surface Hydrophilization for Durable Copper Adhesion
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Solution Overview
Problem
Low-dielectric materials like LCP and PTFE exhibit poor adhesion to copper, leading to increased transmission loss and peeling issues in circuit substrates, and existing methods fail to maintain hydrophilicity for prolonged periods.
Innovation Solution
A resin surface hydrophilization method involving plasma desorption and introduction of hydroxyl groups, followed by metal deposition, using specialized plasma processing devices to enhance adhesion and hydrophilicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the surface of PTFE base member is irradiated with atmospheric plasma to activate the surface, then the adhesion between PTFE and copper is improved, but the hydrophilicity is not maintained for a long period (contact angle remains about 50° after 24 hours)
Solution Approach 1:
The patent changes the chemical composition parameters of the plasma treatment by introducing specific compounds containing hydroxyl groups (such as water, hydrogen peroxide, or carboxylic acid) during plasma irradiation. This modifies the surface chemistry to create stable hydroxyl groups that provide long-lasting hydrophilicity, maintaining contact angles below 10° even after 24 hours, while simultaneously achieving strong adhesion between PTFE and copper.
2Strength
If copper is formed on the surface of base member by chemically roughening the surface, then the physical adhesion between substrate and copper is improved, but the transmission loss of circuit substrate increases
Solution Approach 1:
The patent replaces mechanical/chemical roughening methods with plasma surface treatment that modifies surface chemistry without creating physical roughness. By using plasma to introduce hydroxyl groups and activate the surface, strong adhesion is achieved through chemical bonding rather than mechanical interlocking, thereby avoiding the transmission loss associated with surface roughness while maintaining excellent copper adhesion.
3Strength
If copper is attached to the surface of base member using an adhesive, then the adhesion between base member and copper is improved, but the adhesive layer itself causes transmission loss
Solution Approach 1:
The patent extracts and eliminates the adhesive layer from the structure by directly bonding copper to the PTFE surface through plasma treatment. The plasma-activated surface provides sufficient adhesion strength without requiring any intermediate adhesive material, thereby removing the source of transmission loss associated with adhesive layers while maintaining strong copper attachment.
4Strength
If the surface of PTFE base member is modified by atmospheric plasma, then adhesion is improved, but the manufacturing time is extended (modification time is about 24 hours)
Solution Approach 1:
The patent implements continuous plasma treatment that simultaneously achieves surface activation, hydroxyl group introduction, and hydrophilicity maintenance in a single uninterrupted process. This eliminates the need for separate treatment steps and extended waiting periods, reducing the total manufacturing time while ensuring strong adhesion and long-lasting hydrophilicity are achieved together.
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 achieves long-lasting hydrophilicity, enabling stable metal film formation and strong adhesion between resin and metal, reducing transmission loss and peeling in circuit substrates.
Implementation Method 1
a desorption step of desorbing at least a part of atoms constituting resin from a hydrophobic surface of the resin by irradiating the surface with plasma
Implementation Method 2
an introduction step of introducing a hydroxyl group on the surface of the resin subjected to the desorption step by irradiating the surface of the resin with hydroxyl radicals
Data Source
AI summary
A plasma processing device may include first and second processing devices. The first processing device may include a first chamber, a first exhaust pump which provides, into the first chamber, a first pressure equal to or higher than 0.1 Pa and equal to or lower than 0.3 Pa while depressurizing the first chamber, a first holding unit which holds resin, a first gas introduction unit which introduces, into the first chamber, first gas for desorbing at least a part of atoms constituting the resin from a surface of the resin when turned into plasma, and a first plasma generation unit which turns the first gas into plasma at the first pressure. The second processing device may include a grounded second chamber, a second exhaust pump which provides, into the second chamber, a second pressure equal to or higher than 30% and equal to or lower than 50% of the first pressure at which the desorption step has been performed while depressurizing the second chamber, a second holding unit which holds the resin processed in the first chamber and to which a first DC voltage may be applied, a second gas introduction unit which introduces, into the second chamber, second gas to generate hydroxyl radicals by being turned into plasma, and a second plasma generation unit which turns the second gas into plasma at the second pressure and to which a second DC voltage higher than the first DC voltage may be applied.