Tapered Etching Mask Opening for Wiring Path Void Prevention
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Solution Overview
Problem
Conventional multilayer circuit board manufacturing methods are prone to increased electrical resistance and disconnection issues due to arrangement errors in the etching mask, leading to voids in the wiring paths when the seed layer is removed over the conductive portion.
Innovation Solution
A method involving a tapered outline for the opening in the etching mask, which reduces the width dimension perpendicular to the wiring path's extending direction, ensuring that even if the mask shifts, the seed layer removal does not expose the insulating film over the entire width, thus preventing large voids and maintaining connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a rectangular opening is formed in the etching mask to remove the seed layer, then the wiring path can be formed, but arrangement errors cause the opening to shift and expose the insulating film, creating voids that increase electrical resistance and cause disconnection
Solution Approach 1:
The patent applies asymmetry by changing the opening shape from a symmetric rectangle to an asymmetric tapered shape with two long sides and two short sides. The long sides are positioned such that even when the opening shifts during arrangement, the seed layer removal is limited to the short side regions, preventing exposure of the insulating film over the conductive portion and avoiding void formation that would cause disconnection or increased resistance.
Solution Approach 2:
The patent applies local quality by making different sides of the opening have different lengths, with the long sides extending further than the short sides. This creates localized protection zones along the long sides where the seed layer remains intact, ensuring that even with arrangement errors, the critical areas near the conductive portion are protected from exposure, while allowing selective removal in the short side regions.
2Ease of manufacture
If the etching mask opening is positioned with tolerance to accommodate arrangement errors, then manufacturing is easier, but the opening may cover the entire width of the conductive portion, removing the seed layer completely and causing wiring path disconnection
Solution Approach 1:
The asymmetric tapered opening shape with long and short sides allows for relaxed arrangement tolerances. The long sides extend sufficiently to ensure that even when the opening shifts within the tolerance range, the seed layer is not completely removed from the conductive portion area, maintaining wiring path continuity while accommodating manufacturing variations.
Solution Approach 2:
The patent applies beforehand cushioning by designing the opening shape and positioning the long sides such that they provide a buffer zone. This cushioning effect ensures that even with arrangement errors within the tolerance range, the seed layer removal is limited to specific regions and does not completely expose the insulating film over the conductive portion, preventing wiring path disconnection.
3Manufacturing precision
If the seed layer is completely removed over the conductive portion to form the wiring path opening, then the wiring path can be formed, but any shift in mask position causes complete exposure of the insulating film, creating large voids that significantly increase electrical resistance
Solution Approach 1:
The asymmetric opening shape with long and short sides creates a positioning error buffer. The long sides are positioned to ensure that even when the opening shifts, the seed layer removal is limited to the short side regions, preventing complete exposure of the insulating film over the conductive portion. This maintains stable electrical resistance by avoiding large void formations.
Solution Approach 2:
The patent applies local quality by creating localized seed layer removal zones at the short sides of the opening, while the long sides maintain seed layer coverage over the conductive portion. This ensures that even with positioning variations, the critical areas for electrical conduction are protected, maintaining stable electrical resistance.
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 approach prevents significant increases in electrical resistance and disconnection by minimizing voids in the wiring paths, ensuring reliable coupling between conductive and upper wiring paths, even with etching mask arrangement errors.
Implementation Method 1
removing a part of the seed layer corresponding to an opening portion of the etching mask by an etching process
Implementation Method 2
depositing on the end surface of the conductive portion and the seed layer a conductive material for a wiring path
Data Source
AI summary
In a method for manufacturing a circuit board, as a photomask adapted to form an etching mask for selective removal of a seed layer covering a conductive portion exposed on an insulating film, a photomask whose opening area has an outline having two sides along two straight lines approaching to each other as the two straight lines extend from a center portion of the opening area in an extending direction of a wiring path is used.