PCB Through Hole Plating for Micro Wiring
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Solution Overview
Problem
Conventional methods for manufacturing printed circuit boards struggle to achieve high density wiring with conductors narrower than 50 μm and spaced less than 60 μm due to the thickness of the plated conductor required to fill through holes, limiting the miniaturization of printed circuit board designs.
Innovation Solution
A method involving the formation of tapered through holes in an insulating layer, where a first plated conductor is deposited and then partially removed, leaving a mid-portion within the hole, and a second plated conductor is added to fill the outer portion, allowing for the formation of thin wiring conductors on the surface with widths of 30 μm or less and spatial intervals of 30 μm or less using a semi-additive process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the plated conductor thickness is increased to fill through holes, then the reliability of through hole filling is improved, but the wiring conductor width and spatial interval cannot be reduced below approximately 50 μm and 60 μm
Solution Approach 1:
The plated conductor formation process is segmented into two distinct stages: first forming a thick plated conductor to reliably fill the through hole, then selectively removing portions and adding a second plated conductor to form the final wiring conductor. This segmentation allows the through hole filling and wiring conductor formation to be optimized independently, resolving the contradiction between reliability and manufacturing precision.
Solution Approach 2:
The invention extracts the through hole filling function from the wiring conductor formation process. By using a first plated conductor specifically for filling the through hole and then removing excess portions, the thick plated conductor needed for reliability is separated from the final wiring conductor dimensions, enabling narrow wiring conductors with precise spatial intervals.
2Manufacturing precision
If the plated conductor thickness is reduced to enable narrow wiring conductors, then the wiring conductor width can be reduced to 30 μm or less, but the through holes cannot be properly filled
Solution Approach 1:
The invention segments the plated conductor into two functional parts: a first plated conductor that fills the through hole with sufficient thickness for reliability, and a second plated conductor that forms the narrow wiring conductor on the surface. This segmentation allows each part to have the appropriate thickness for its specific function, resolving the contradiction between narrow wiring width and proper through hole filling.
Solution Approach 2:
The first plated conductor is formed in advance to fill the through hole with the necessary thickness for reliability. After this preliminary action, excess portions are removed and the second plated conductor is added to form the final narrow wiring conductor. This preliminary action ensures through hole filling reliability is established before finalizing the wiring conductor dimensions.
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 enables the creation of thin type printed circuit boards with high density wiring by reducing the thickness of the surface conductors to 20 μm or less, facilitating the formation of micro wiring conductors with narrower widths and closer spacing, thereby overcoming the limitations of conventional manufacturing techniques.
Implementation Method 1
forming a first plated conductor at least in the through hole and on the upper and lower surfaces around the through hole
Implementation Method 2
removing the first plated conductor overlying and underlying a periphery of the through hole by etching the first plated conductor
Implementation Method 3
forming by semi-additive method a second plated conductor that fills an outer portion than the first plated conductor in the through hole, and forms a wiring conductor on the upper and lower surfaces
Data Source
AI summary
A method of manufacturing a printed circuit board includes forming a through hole 2 in an insulating layer 1 having upper and lower faces so as to penetrate between the upper and lower surfaces; allowing a first plated conductor 4 to be deposited at least in the through hole 2 and on the upper and lower surfaces around the through hole; removing the first plated conductor overlying and underlying a periphery of the through hole by etching the first plated conductor 4, while leaving at least the first plated conductor 4 in a mid-portion in a vertical direction within the through hole 2; and forming by semi-additive method a second plated conductor 6 that fills an outer portion than the first plated conductor 4 in the through hole 2, and forms a wiring conductor on the upper and lower surfaces.