Carrier-Attached Copper Foil Light Absorbance Circuit Precision
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Solution Overview
Problem
The challenge in manufacturing printed wiring boards is the difficulty in forming precise fine pitch circuits due to the defective geometry of the plating resist, which leads to inaccurate circuit formation on ultra-thin copper layers, caused by light transmission and reflection issues during the curing process.
Innovation Solution
A carrier-attached copper foil with a surface ultra-thin copper layer having a light absorbance of 85% or more at 400 nm wavelength is used, combined with a roughened layer and a resin layer, to control light absorption and improve circuit formability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the copper foil thickness is made thinner to achieve finer pitch circuits, then the circuit precision is improved, but the handling property deteriorates
Solution Approach 1:
The ultra-thin copper layer (5 μm or less) is nested on the thick metal foil carrier (10-50 μm), creating a composite structure where the thin copper layer provides fine pitch circuit precision while the thick carrier provides easy handling properties during manufacturing processes
2Productivity
If a light-transmissive plating resist is used for curing, then the resin penetration is improved, but the circuit geometry precision deteriorates due to light reflection
Solution Approach 1:
The light reflection from the ultra-thin copper layer surface, which was previously harmful causing over-curing and geometry defects, is converted into a beneficial effect by controlling the reflectance to enhance light penetration into the resin layer while maintaining precise circuit geometry through optimized absorbance characteristics
Solution Approach 2:
The optical parameters of the ultra-thin copper layer are changed by controlling its absorbance of light at 400 nm wavelength to be 85% or more, which optimizes the balance between light absorption for precise resist curing and light reflection for enhanced resin penetration
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
This solution enables precise control of the curing process, allowing for the formation of circuits with improved geometry and precision on the surface of ultra-thin copper layers, enhancing the overall circuit formability and accuracy in printed wiring boards.
Implementation Method 1
a surface of the ultra-thin copper layer has an absorbance of light at a wavelength of 400 nm of 85% or more
Data Source
AI summary
A carrier-attached copper foil having satisfactory circuit formability on the ultra-thin copper layer surface is provided. The carrier-attached copper foil has a carrier, an intermediate layer and an ultra-thin copper layer in this order. The ultra-thin copper layer surface has an absorbance of light at a wavelength of 400 nm is 85% or more.