Copper-Tin Alloy Layer Bondability and Removal
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Solution Overview
Problem
Existing electroconductive layers face issues with bondability to resin layers, particularly under severe conditions, and difficulty in removing tin layers or copper-tin alloy layers, which can lead to defects like hallowing and power loss in transmission lines.
Innovation Solution
A copper layer with a copper-tin alloy layer of specific thickness (0.001 to 0.020 μm) is formed, where the copper-tin alloy layer is created through tin plating and subsequent stripping, ensuring strong bondability and easy removal, while preventing diffusion and thickness increase over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a tin layer is formed on the copper layer surface to improve bondability to resin layer, then bondability is improved, but the tin layer becomes difficult to remove in subsequent steps and may hinder plating treatment
Solution Approach 1:
The patent changes the thickness parameter of the tin layer from conventional thick layers (1 μm or more) to a thin layer (0.01 to 0.5 μm). This parameter change allows the tin layer to maintain sufficient bondability to the resin layer while enabling easy removal in subsequent plating steps without requiring excessive etching that would damage wiring patterns.
2Strength
If the copper layer surface is made rough by etching to express anchor effect, then bondability is improved, but irregularities increase power loss in transmission lines
Solution Approach 1:
The patent applies local quality by forming a tin layer only on specific regions of the copper layer surface where bondability is needed, rather than making the entire surface rough through etching. The tin layer provides the necessary anchoring effect locally at the interface with the resin layer, while maintaining a smooth overall surface that minimizes power loss in transmission lines.
3Strength
If a thick tin layer is used to ensure bondability, then bondability is improved, but diffusion between tin and copper advances with time and removal becomes difficult
Solution Approach 1:
The patent changes the thickness parameter of the tin layer to a thin configuration (0.01 to 0.5 μm), which reduces the total amount of tin present. This reduces the extent of diffusion between tin and copper over time, preventing the formation of a thick copper-tin alloy layer that would be difficult to remove. The thin tin layer maintains sufficient bondability while minimizing long-term diffusion issues.
4Strength
If black oxide or brown oxide is formed on copper layer to improve bondability, then bondability is improved, but the oxide is dissolved by acidic solution in plating step causing hallowing defect
Solution Approach 1:
The patent uses a thin tin layer as a temporary bonding enhancement that serves its purpose during the resin lamination process and then can be easily removed in subsequent steps. Unlike black oxide or brown oxide that cause hallowing defects when exposed to acidic plating solutions, the thin tin layer provides the necessary bondability improvement without compromising the reliability of subsequent plating operations.
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 maintains bondability between the electroconductive and resin layers, facilitates easy removal of the copper-tin alloy layer, and prevents thickness increase, thus addressing defects and power loss issues.
Implementation Method 1
a copper layer and a copper-tin alloy layer laminated over the copper layer
Implementation Method 2
diffusion between tin in the layer and copper in an underlying layer thereof advances with the passage of time
Data Source
AI summary
The object of the present invention is to provide an electroconductive layer that retains bondability to a resin layer certainly and is further a layer from which a copper-tin alloy layer is easily removed in a subsequent step, a laminate using this layer, and producing processes thereof. The electroconductive layer of the present invention is an electroconductive layer which is to be bonded to a resin layer, and which contains a copper layer and a copper-tin alloy layer laminated over the copper layer, wherein the copper-tin alloy layer has a thickness of 0.001 to 0.020 μm.