Surface-Treated Copper Foil Layers for High-Temperature Adhesion
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Solution Overview
Problem
Existing copper foils used in high-frequency signal transmission experience adhesion loss and increased insertion loss when exposed to high temperatures due to oxidation and deformation of roughening particles, despite efforts to reduce surface roughness and magnetic metal deposition.
Innovation Solution
A surface-treated copper foil with a roughening treatment layer of 0.5 μm to 0.9 μm copper particles, a heat-resistant layer containing cobalt and molybdenum, and a chromate treatment layer with a gloss of 60 to 80, enhancing adhesion and heat resistance on low-dielectric resin substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If copper foil undergoes fine roughening treatment with small primary particle size to reduce insertion loss, then insertion loss decreases, but adhesion strength deteriorates due to oxidation and particle deformation at high temperature
Solution Approach 1:
The surface treatment is divided into multiple distinct layers: a roughening treatment layer with copper particles for adhesion, a heat-resistant treatment layer containing cobalt and molybdenum for oxidation protection, and a chromate treatment layer for additional corrosion resistance. This segmentation allows each layer to perform its specific function without interfering with others, resolving the contradiction between maintaining adhesion and preventing high-temperature degradation.
Solution Approach 2:
The invention uses a composite surface structure combining copper particles (for adhesion), cobalt-molybdenum alloy (for heat resistance and oxidation protection), and chromium (for corrosion resistance). This composite approach allows the surface to simultaneously achieve low insertion loss through controlled roughness while maintaining adhesion strength through the protective heat-resistant layer that prevents copper particle oxidation and deformation at forming temperatures of 300°C or higher.
2Loss of energy
If copper foil surface roughness is reduced to lower insertion loss at high frequency, then signal transmission quality improves, but adhesion to insulating resin substrate deteriorates
Solution Approach 1:
The surface treatment is divided into multiple distinct layers: a roughening treatment layer with copper particles for adhesion, a heat-resistant treatment layer containing cobalt and molybdenum for oxidation protection, and a chromate treatment layer for additional corrosion resistance. This segmentation allows each layer to perform its specific function without interfering with others, resolving the contradiction between maintaining adhesion and preventing high-temperature degradation.
Solution Approach 2:
The invention optimizes the primary particle size of copper particles in the roughening treatment layer to 0.5 μm to 0.9 μm, which provides sufficient adhesion while controlling surface roughness. Additionally, the heat-resistant treatment layer containing cobalt and molybdenum in specific proportions (Co: 0.01-5 μm, Mo: 0.01-5 μm) protects the copper particles from oxidation and deformation, maintaining adhesion strength even when surface roughness is controlled for low insertion loss.
3Ease of manufacture
If copper foil is exposed to high temperature (300°C or higher) for forming low-dielectric resin substrate, then substrate forming is achieved, but copper surface oxidizes and particles deform causing adhesion loss
Solution Approach 1:
The heat-resistant treatment layer containing cobalt and molybdenum is formed on the copper foil surface before the high-temperature substrate forming process. This preliminary protective layer prevents oxidation and particle deformation during the subsequent 300°C or higher forming process, allowing the substrate to be formed successfully while maintaining adhesion strength. The chromate treatment layer is also applied in advance for additional corrosion resistance during the high-temperature process.
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 copper foil maintains high adhesion and low insertion loss even at temperatures above 300°C, suitable for high-frequency signal transmission with improved durability and performance.
Implementation Method 1
a roughening treatment layer formed of copper particles having a primary particle size of 0.5 μm to 0.9 μm and therefore has a superior anchor effect on an insulating resin substrate
Implementation Method 2
the surface of the roughening treatment layer is less susceptible to oxidation, and the copper particles are also less susceptible to deformation
Implementation Method 3
a chromate treatment layer containing chromium on the heat-resistant treatment layer
Data Source
AI summary
A surface-treated copper foil includes a roughening treatment layer on at least one surface of an untreated copper foil, a heat-resistant treatment layer on the roughening treatment layer, and a chromate treatment layer on the heat-resistant treatment layer. The roughening treatment layer is formed of copper particles having a primary particle size of 0.5 μm or more and 0.9 μm or less. The heat-resistant treatment layer is a heat-resistant treatment layer containing cobalt and molybdenum. The chromate treatment layer has a treatment surface with a gloss Gs (85°) of 60 or more and 80 or less.