Asymmetric Via Geometry for Void-Free Plating
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Solution Overview
Problem
Existing printed wiring boards with hourglass-shaped through-hole conductors face challenges in filling plating evenly, leading to voids in the second opening portion, which can cause line disconnection and malfunctions, especially when the volume of the second opening portion is greater than the first, making it difficult to form fine conductive circuits and increasing the risk of warping.
Innovation Solution
A method involving laser irradiation to form a penetrating hole with a first opening portion and a second opening portion of varying depths and volumes, where the second opening portion has a greater volume and includes a void, allowing for the formation of a through-hole conductor with an electrolytic plated material that connects the conductive layers, while inhibiting plating solution circulation to reduce void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the second opening portion has a greater volume than the first opening portion, then the through-hole conductor can accommodate larger conductive structures, but plating solution circulation causes void formation leading to line disconnection and malfunctions
Solution Approach 1:
The penetrating hole is divided into two distinct opening portions: a first opening portion on the first surface and a second opening portion on the second surface. This segmentation allows independent control of plating in each region, enabling the larger second opening portion to be filled without causing circulation-induced voids that would compromise conductor reliability.
Solution Approach 2:
Different regions of the penetrating hole are given different properties: the first opening portion has a smaller volume optimized for complete plating filling, while the second opening portion has a larger volume for accommodating conductive structures. This local differentiation resolves the contradiction by ensuring reliable plating in the first portion while maintaining the required volume in the second portion.
2Quantity of substance
If the second opening portion has a greater depth and volume, then more electrolytic plated material can be deposited, but plating solution circulation creates voids that cause malfunctions
Solution Approach 1:
The plating process is segmented into two zones: the first opening portion where complete material deposition occurs without circulation voids, and the second opening portion where larger volume is accommodated. This segmentation enables sufficient plated material quantity while preventing void formation that would cause malfunctions.
Solution Approach 2:
The first opening portion is designed to be filled with plated material first, establishing a reliable conductive base before the plating process extends to the second opening portion. This preliminary action ensures that the critical connection region is void-free while still allowing sufficient material deposition in the larger second portion.
3Manufacturing precision
If the penetrating hole has asymmetric opening portions with different volumes, then fine conductive circuits can be formed, but warping risk increases
Solution Approach 1:
The asymmetric design is applied locally to the opening portions rather than the entire structure. The first opening portion maintains a controlled, smaller volume for precise circuit formation, while the second opening portion accommodates larger conductive structures. This localized asymmetry enables fine circuit precision while the overall symmetric hourglass shape maintains structural stability against warping.
Solution Approach 2:
The penetrating hole employs asymmetric opening portions with different volumes and depths to enable fine conductive circuit formation. The first opening portion has smaller volume for precision, while the second has larger volume for conductive structure accommodation. This controlled asymmetry achieves manufacturing precision for fine circuits while the hourglass shape maintains overall structural balance.
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 approach enhances the reliability of through-hole conductors by minimizing the impact of voids, reducing warping, and ensuring stable connections, even when the through-hole conductor in the second opening portion includes a void, thus preventing line disconnection and malfunctions, and allowing for the formation of fine conductive circuits.
Implementation Method 1
irradiating laser on a first surface of an insulative substrate such that a first opening portion is formed on a first-surface side of the insulative substrate, irradiating laser on a second surface of an insulative substrate such that a second opening portion connected to the first opening portion is formed
Implementation Method 2
filling an electrolytic plated material into a space formed by the seed layer in the penetrating hole of the insulative substrate such that a through-hole conductor including the electrolytic plated material is formed
Data Source
AI summary
A printed wiring board includes an insulative substrate having a penetrating hole, a first conductive layer formed on a first surface of the insulative substrate, a second conductive layer formed on a second surface of the insulative substrate, and a through-hole conductor formed in the penetrating hole through the insulative substrate such that the through-hole conductor is connecting the first conductive layer and second conductive layer. The penetrating hole has a first opening portion formed on a first-surface side of the insulative substrate and a second opening portion formed on a second-surface side of the insulative substrate such that the second opening portion has a depth which is greater than a depth of the first opening portion and the second opening portion has a volume which is greater than a volume of the first opening portion, and the through-hole conductor formed in the second opening portion includes a void portion.