Anisotropic Etching Additives for PCB Conductor Tracks
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Solution Overview
Problem
Conventional copper etching processes face challenges in achieving anisotropic etching for fine structures on printed circuit boards, leading to poor adhesion and inability to form regular shapes due to isotropic etching, which results in undercuts and defects.
Innovation Solution
An etching composition comprising an etchant, a polymer compound with surface-active properties, and a polyhydric compound is used to promote anisotropic etching by adsorbing on side walls and adjusting viscosity, preventing lateral etching and enhancing vertical etching, thereby forming conductor tracks with regular shapes and improved quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If isotropic etching is used, then the etching process is simple and easy to implement, but undercuts are formed beneath the mask resulting in poor adhesion and irregular shapes
Solution Approach 1:
A polymer compound is introduced as an intermediary substance that selectively adsorbs to the lateral etching surfaces, acting as a protective barrier that prevents etchant from attacking the sidewalls. This mediator enables anisotropic etching by blocking lateral etching while allowing vertical etching to proceed, thereby forming vertical sidewalls and regular shapes without undercuts
Solution Approach 2:
The etching composition's chemical parameters are modified by adding specific polymers and polyhydric compounds that change the etching behavior from isotropic to anisotropic. The polymer concentration, molecular weight, and chemical composition are optimized to achieve selective adsorption on lateral surfaces, transforming the etching profile from undercut-prone to vertical-sided
2Manufacturing precision
If anisotropic etching is used to form fine structures, then regular shapes with vertical side walls are achieved, but the etching process becomes more complex and requires specific additives
Solution Approach 1:
The polymer compound serves multiple functions simultaneously: it acts as a sidewall protective layer, a viscosity modifier, and a process control agent. This multi-functional additive simplifies the overall process by combining several roles into one substance, reducing the need for multiple separate process steps or additives
Solution Approach 2:
The etching composition is formulated as a composite system combining etchant, polymer compound, and polyhydric compound. This composite approach leverages the synergistic effects of different components where the polymer provides structural protection and the polyhydric compound adjusts rheological properties, achieving complex anisotropic etching through a coordinated material system
3Productivity
If conventional etching is used, then the process is fast and efficient, but it cannot form very fine etching structures and is blocked by fine mask structures
Solution Approach 1:
The etching composition exhibits spatially varying etching rates through selective polymer adsorption. The polymer concentrates on lateral surfaces where it provides protective effects, while the bottom of the etched feature remains more accessible to the etchant. This local differentiation in etching behavior enables fine structure formation while maintaining overall etching efficiency
4Manufacturing precision
If anisotropic etching additives are used, then lateral etching is suppressed and vertical etching is enhanced, but the etching composition may become hazardous to health and environment
Solution Approach 1:
The chemical parameters of the etching system are optimized by selecting biocompatible polymers and polyhydric compounds with specific molecular weights and functional groups. These parameter optimizations maintain the anisotropic etching effect while ensuring the additives are non-toxic and environmentally friendly, replacing hazardous conventional etching chemicals
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 effectively reduces defects and improves etching distribution, achieving higher etching factors and finer line widths, while being non-toxic and environmentally friendly.
Implementation Method 1
the etching additive and/or the organic substance, in particular the polymer compound comprised, may adsorb at (adhere to) the surface of the side walls of a recess (cavity) formed in the electrically conductive layer structure during etching
Implementation Method 2
the polymer compound and/or the polyhydric compound contained in the etching composition may provide for a shear thinning/pseudoplastic behavior and/or a viscosity-optimizing effect
Data Source
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AI summary
An etching composition for etching an electrically conductive layer structure for forming a conductor track is provided which comprises an etchant, an etching additive comprising a polymer compound, an organic substance comprising a polyhydric compound and optionally a solvent. In addition, a method of etching an electrically conductive layer structure, a conductor track, and a component carrier are provided.