PCB Surface Roughness for Adhesion and Roll Mark Control
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Solution Overview
Problem
Conventional surface treatment methods for printed circuit boards (PCBs) fail to achieve high interlayer adhesion and are prone to roll marks during the horizontal roll process, especially when using high reliability materials like BT resin with low dielectric constant and high glass transition temperature, leading to insufficient peel strength and surface defects.
Innovation Solution
A two-stage surface roughness treatment process involving an anchor structure formed by etching and a needle or granular black oxide layer formed through black-oxide treatment, with optional post-dipping using reducing or dissolving agents to enhance acid resistance and reduce black oxide layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional surface treatment methods (brown oxide or black oxide) are used, then the PCB can be manufactured with standard processes, but the interlayer adhesion is insufficient and roll marks occur during horizontal roll process
Solution Approach 1:
The patent changes the chemical composition parameters of the black oxide treatment solution by adding specific additives (such as hydroquinone, ascorbic acid, or EDTA) to control the oxidation process. This parameter modification enables the formation of a thinner black oxide layer (50-200 nm) that provides sufficient adhesion without causing roll marks during horizontal rolling
Solution Approach 2:
The patent creates a localized surface structure by forming black oxide specifically on the copper pattern surfaces while maintaining different properties in different areas. The black oxide layer is formed selectively on the metal patterns to provide adhesion where needed, while the overall surface maintains smoothness to prevent roll marks
2Strength
If black oxide layer thickness is increased to improve adhesion, then interlayer bonding strength increases, but roll marks are generated during horizontal roll process
Solution Approach 1:
The patent optimizes the black oxide layer thickness parameter to a specific range (50-200 nm) through controlled treatment time and solution composition. This optimized thickness provides adequate adhesion strength (peel strength >0.4 kgf/cm) while being thin enough to prevent roll mark formation during horizontal rolling
Solution Approach 2:
The patent applies black oxide treatment selectively only on the copper pattern surfaces rather than the entire substrate surface. This partial action provides adhesion where it is most needed for interlayer bonding while minimizing the total oxide layer area that could cause roll marks
3Reliability
If etching process is applied to form anchor structure, then interlayer adhesion is improved, but surface roughness increases which may affect subsequent processing
Solution Approach 1:
The patent modifies the etching process parameters including solution composition (using ammonium persulfate, ferric chloride, or cupric chloride), temperature (60-80°C), and treatment time to create an anchor structure with controlled roughness. The etching forms microscopic anchors that provide adhesion while maintaining overall surface smoothness
Solution Approach 2:
The patent creates a segmented surface structure with anchor points distributed across the copper surface. The etching process forms discrete anchor structures (micrometer-scale protrusions) that provide adhesion without creating continuous surface roughness that would affect subsequent processing
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 method significantly improves interlayer adhesion with prepregs having specific properties, reduces roll marks, and maintains acid resistance, achieving peel strengths above 0.4 kgf/cm and efficient production by controlling the black oxide layer thickness between 0.05 to 1.0 mg/cm2.
Implementation Method 1
treating a metal surface for a circuit with an etching solution for forming an anchor structure to form a first surface roughness in an anchor structure
Implementation Method 2
subjecting the metal surface into a black-oxide treatment to form a second surface roughness having a black oxide layer in a needle structure
Implementation Method 3
a post-dipping process using a reducing agent and an alkali material is carried out to enable reduction of a surface of the black oxide layer
Data Source
AI summary
Disclosed herein are a printed circuit board and a method for manufacturing the same. The printed circuit board includes: a base substrate having a metal pattern for a circuit; and a surface roughness provided on the metal pattern, wherein the surface roughness has a first surface roughness in an anchor structure and a second surface roughness having a black oxide layer in a needle structure formed on the first surface roughness.