Hard Rolled-Copper Foil Crystal Orientation Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hard rolled-copper foils with high final reduction ratios exhibit increased surface roughness and softening temperatures, leading to degraded high-speed transmission characteristics and room temperature softening, which affects the efficiency and yield of flexible printed wiring boards.
Innovation Solution
A hard rolled-copper foil with a crystal orientation density of 10 or more in the copper orientation and 20 or more in the brass orientation, manufactured using a process involving final heat treatment at a recovery temperature range and subsequent cold rolling at a reduction ratio between 70% and 90%, maintaining low surface roughness and preventing room temperature softening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the final reduction ratio is increased to improve bending-resistance characteristics, then the bending-resistance characteristics are improved, but the surface roughness increases and high-speed transmission characteristics are degraded
Solution Approach 1:
The patent changes the crystal orientation parameters by controlling the final reduction ratio within a specific range (70-90%) and applying heat treatment at specific temperatures to develop copper orientation and brass orientation. This parameter optimization achieves the required bending-resistance characteristics while preventing excessive surface roughness that would degrade high-speed transmission characteristics.
2Strength
If the final reduction ratio is increased to improve bending-resistance characteristics, then the bending-resistance characteristics are improved, but the softening temperature decreases causing room temperature softening
Solution Approach 1:
The patent optimizes the final reduction ratio to within 70-90% and applies heat treatment at controlled temperatures to develop specific crystal orientations (copper orientation and brass orientation). This parameter control achieves improved bending-resistance characteristics while maintaining the softening temperature above room temperature, preventing room temperature softening that would affect operation efficiency and foil passing property.
3Ease of manufacture
If heat treatment is performed to soften the rolled copper for easy working, then the rolled copper becomes soft and easily worked, but the bending-resistance characteristics are reduced
Solution Approach 1:
The patent performs heat treatment at a stage before the final cold rolling to develop copper orientation and brass orientation in advance. This preliminary heat treatment creates a crystal structure that will provide excellent bending-resistance characteristics after the final cold rolling, rather than softening the copper after all rolling is complete. This timing of the heat treatment allows the copper to be easily worked during final rolling while ensuring high bending-resistance in the finished product.
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 provides excellent bending-resistance and high-speed transmission characteristics while preventing room temperature softening, ensuring high product yield and efficient operation of flexible printed wiring boards.
Implementation Method 1
Since the rolled copper is subjected to work hardening during the cold rolling process
Implementation Method 2
the heat treatment is performed in order to again create a state in which the rolled copper is soft and easily worked
Implementation Method 3
This heat treatment is also referred to as annealing and is typically performed by holding the rolled copper at 200° C. for one hour in an inert atmosphere or under vacuum
Implementation Method 4
a rolled copper is softened in sequence in accordance with the degree of progress of heat treatment through a process called 'recovery'
Implementation Method 5
a rolled copper is softened in sequence in accordance with the degree of progress of heat treatment through a process called 'recovery'+'recrystallization'
Implementation Method 6
a rolled copper is softened in sequence in accordance with the degree of progress of heat treatment through a process called 'recovery'+'recrystallization'+'grain growth'
Data Source
AI summary
A hard rolled-copper foil which, when heated and laminated on an insulating resin base material, can exhibit excellent bend-resistance characteristics without increasing a final reduction ratio, which, being not prone to develop rolling marks, can maintain a low surface coarseness and can therefore be preferably used in a flexible printed wiring board having excellent high-speed transmission characteristics, which is not prone to softening at room temperature, and which provides excellent operation efficiency and foil passing property when being processed into a flexible printed wiring board after having been stored. A hard rolled-copper foil in which a crystal orientation density in a copper orientation is not less than 10, and a crystal orientation density in a brass orientation is not less than 20.