Semi-Additive PCB Micro Wiring Adhesion and Resist Stripping
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Solution Overview
Problem
Conventional methods for producing micro wiring on printed-wiring boards face challenges with adhesion between the copper seed layer and dry film resist, leading to defects like disconnection and insufficient resist stripping, especially when forming patterns narrower than 10 μm.
Innovation Solution
A semi-additive process involving a specific etching solution with hydrogen peroxide, sulfuric acid, halogen ion, and tetrazoles for copper surface roughening, followed by a resist stripping liquid with monoethanolamine, quaternary ammonium hydroxide, ethylene glycols, and azoles to improve adhesion and resist stripping without residue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the insulation layer surface is coarsely roughened to ensure adhesion of chemical copper plating, then adhesion between insulation layer and seed layer is improved, but surface roughness increases (Ra: 0.4 to 1 μm) causing light scattering that prevents formation of fine patterns with wiring width less than 10 μm
Solution Approach 1:
The invention changes the surface roughness parameter of the seed layer from coarse (Ra: 0.4-1 μm) to fine level (Ra: 0.05-0.3 μm) through controlled etching treatment, enabling both adequate adhesion and light penetration for fine pattern formation with wiring width less than 10 μm
Solution Approach 2:
The invention introduces an intermediary etching treatment step between the insulation layer roughening and the final plating process. This intermediary step modifies the seed layer surface to have fine roughness that mediates between the need for adhesion and the need for optical clarity in photolithography
2Shape
If a smooth copper surface (chemical copper plating or sputtered copper) is used as seed layer, then surface flatness is improved, but adhesion to dry film resist material becomes insufficient making pattern formation impossible
Solution Approach 1:
The invention changes the surface morphology parameter of the copper seed layer from perfectly smooth to fine roughness (Ra: 0.05-0.3 μm) through etching treatment, creating sufficient surface area and anchoring points for dry film resist adhesion while maintaining overall flatness for pattern formation
3Ease of operation
If conventional resist stripping liquid containing sodium hydroxide is used, then dry film resist can swell and strip adequately, but when resist pattern width is less than 10 μm, the space between adjacent patterns is narrow preventing sufficient swelling and stripping
Solution Approach 1:
The invention changes the chemical composition parameters of the resist stripping liquid by replacing or supplementing sodium hydroxide with alternative stripping agents that have different swelling mechanisms, enabling effective stripping of sub-10 μm patterns without requiring extensive swelling space
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 enhances adhesion between the copper seed layer and dry film resist, reduces defects, and allows for reliable formation of micro wiring with improved resist stripping properties, addressing the limitations of conventional processes.
Implementation Method 1
subjecting the obtained copper surface to a roughening treatment using an etching solution containing 0.1 to 3% by mass of hydrogen peroxide, 0.3 to 5% by mass of sulfuric acid, 0.1 to 3 ppm of halogen ion and 0.003 to 0.3% by mass of tetrazoles
Implementation Method 2
subjecting the remaining dry film resist to a stripping treatment using a resist stripping liquid containing 0.5 to 20% by mass of monoethanolamine, 0.2 to 10% by mass of quaternary ammonium hydroxide, 0.01 to 10% by mass of ethylene glycols and 0.01 to 0.5% by mass of azoles
Data Source
AI summary
The present invention provides a method for producing a printed-wiring board in a semi-additive process, comprising the steps of: providing a chemical copper plating 4 on an insulation layer 3 or forming a copper thin film on the insulation layer 3 using a sputtering method; subjecting the obtained copper surface 4 to a roughening treatment using an etching solution containing 0.1 to 3% by mass of hydrogen peroxide, 0.3 to 5% by mass of sulfuric acid, 0.1 to 3 ppm of halogen ion and 0.003 to 0.3% by mass of tetrazoles; attaching a dry film resist 5 to the copper surface 4 after the roughening treatment to perform exposure and development and providing an electrolytic copper plating 7 to an opening 6 after the exposure; and subjecting the remaining dry film resist to a stripping treatment using a resist stripping liquid containing 0.5 to 20% by mass of monoethanolamine, 0.2 to 10% by mass of quaternary ammonium hydroxide, 0.01 to 10% by mass of ethylene glycols and 0.01 to 0.5% by mass of azoles.