Antireflective Layer for Coreless PCB Wiring Visibility
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Solution Overview
Problem
In the manufacturing of multilayer printed wiring boards, the existing coreless build-up process faces challenges in achieving high visibility of the wiring layer during image inspection due to insufficient visual contrast after copper flash etching, and the antireflective layers used are often etched away by the copper flash etching solution, compromising chemical resistance and visibility.
Innovation Solution
A copper foil with a carrier is developed, featuring a release layer, an antireflective layer composed of metals like Cr, W, Ta, Ti, Ni, and Mo with a surface aggregate of metal particles, and an extremely-thin copper layer. The antireflective layer is formed using magnetron sputtering and provides high chemical resistance and visibility during image inspection by remaining intact after copper flash etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an antireflective layer is provided between the release layer and the extremely-thin copper layer to improve visibility during image inspection, then the visual contrast is improved, but the antireflective layer is etched away by the copper flash etching solution, compromising chemical resistance
Solution Approach 1:
The patent applies composite materials by creating a multilayer structure consisting of a release layer, an antireflective layer, and an extremely-thin copper layer. Each layer is carefully selected to provide specific functions: the release layer enables separation, the antireflective layer (made from materials like chromium, tungsten, tantalum, titanium, nickel, or molybdenum) provides high visual contrast for image inspection while maintaining chemical resistance, and the copper layer provides electrical conductivity. This composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The patent applies local quality by optimizing the properties of each layer for its specific function. The antireflective layer is designed with specific material composition and thickness (1 nm to 300 nm) to provide high visual contrast while maintaining sufficient chemical resistance. The surface of the antireflective layer is engineered to have aggregate metal particles that enhance light scattering and visibility during image inspection, while the bulk material maintains chemical stability against the copper flash etching solution.
2Length of moving object
If the thickness of the extremely-thin copper layer is reduced to miniaturize the embedded circuit, then the circuit size is reduced, but the visibility during image inspection deteriorates due to insufficient visual contrast
Solution Approach 1:
The patent introduces an intermediary antireflective layer between the release layer and the extremely-thin copper layer to solve the visibility problem. This intermediary layer serves as a mediator that enhances the visual contrast during image inspection without requiring the copper layer to be thicker. The antireflective layer, with its aggregate metal particles on the surface, scatters light effectively to provide high contrast, allowing the extremely-thin copper layer (1 nm to 300 nm) to maintain both miniaturization and visibility.
3Reliability
If magnetron sputtering is used to form the antireflective layer with aggregate metal particles on the surface, then the visual contrast and chemical resistance are improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent replaces conventional deposition methods with magnetron sputtering technology to form the antireflective layer. This substitution enables precise control over the material deposition process, creating a layer with aggregate metal particles on the surface that provide both high visual contrast and chemical resistance. The magnetron sputtering process allows for better material utilization, more uniform thickness control (1 nm to 300 nm), and enhanced surface morphology control compared to traditional deposition methods, justifying the increased process complexity through superior product performance.
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 enhances the visibility of the wiring layer during image inspection and maintains chemical resistance against the copper flash etching solution, reducing erosion of the wiring layer and ensuring accurate image inspection, thus improving the manufacturing efficiency of printed wiring boards.
Implementation Method 1
The antireflective layer is formed using magnetron sputtering
Implementation Method 2
at least the surface adjacent to the extremely-thin copper layer of the antireflective layer comprises an aggregate of metal particles
Data Source
AI summary
There is provided a copper foil provided with a carrier providing excellent chemical resistance against the copper flash etching solution during the formation of the wiring layer on the surface of the coreless support and excellent visibility of the wiring layer due to high contrast to the antireflective layer in image inspection after copper flash etching. The copper foil provided with a carrier comprises a carrier; a release layer provided on the carrier; an antireflective layer provided on the release layer and composed of at least one metal selected from the group consisting of Cr, W, Ta, Ti, Ni and Mo; and an extremely-thin copper layer provided on the antireflective layer; wherein at least the surface adjacent to the extremely-thin copper layer of the antireflective layer comprises an aggregate of metal particles.