Multilayer Wiring Board Void-Free Interlayer Connection
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Solution Overview
Problem
In multilayer wiring boards, the overhang of metal foil at the opening of holes for interlayer connection causes plating voids due to the electrolytic filling plating layer blocking the opening before filling the inside, especially with increasing miniaturization and thinner insulating layers, existing methods fail to completely eliminate voids.
Innovation Solution
A multilayer wiring board design where the hole for interlayer connection is filled with at least two layers of electrolytic filling plating, with the lower space between the overhang and the hole's inner wall filled by an inner layer except for the outermost layer, ensuring the maximum diameter inside is equal to or larger than the opening's minimum diameter, and using a two-stage electrolytic filling process to manage current density and prevent voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electrolytic filling plating is used to fill holes for interlayer connection, then the hole can be filled with conductive material, but plating voids occur when the overhang of metal foil blocks the opening before the inside is filled
Solution Approach 1:
The electrolytic filling plating process is divided into multiple stages with different current densities. The first stage uses a first electric current density to initially fill the hole, and the second stage uses a second electric current density (higher than the first) to complete the filling and eliminate voids. This segmentation of the plating process allows controlled filling that prevents void formation caused by the overhang blocking effect.
Solution Approach 2:
The electric current density parameter is changed between two stages of the electrolytic filling plating process. By adjusting the current density from a lower first value to a higher second value, the plating rate and filling behavior are optimized to ensure complete filling of the hole interior without void formation, overcoming the blocking effect of the metal foil overhang.
2Volume of moving object
If the diameter of the hole for interlayer connection is reduced for miniaturization, then the wiring board can be more compact, but the overhang becomes relatively larger and plating voids occur more easily
Solution Approach 1:
By changing the electric current density parameter between two plating stages, the invention enables reliable filling of smaller diameter holes where the overhang blocking effect is more pronounced. The adjusted current density parameters compensate for the relative increase in overhang size, maintaining filling effectiveness despite miniaturization.
Solution Approach 2:
The electrolytic filling plating process is made dynamic by adjusting the electric current density during the plating operation. This dynamic control allows the process to adapt to the specific geometry of miniaturized holes with prominent overhangs, ensuring complete filling without voids even as hole dimensions are reduced for compact wiring boards.
3Ease of manufacture
If conventional electrolytic filling plating methods are used, then the process is simple, but voids cannot be completely eliminated even with controlled current density
Solution Approach 1:
The electrolytic filling plating process is segmented into two distinct stages with different current density parameters. This segmentation, while adding a process step, provides precise control over the filling behavior to eliminate voids, achieving better manufacturing precision that justifies the additional process complexity.
Solution Approach 2:
The electrolytic filling plating is performed in periodic stages with alternating current density levels. The first stage uses a lower current density for initial filling, and the second stage uses a higher current density to eliminate voids. This periodic variation in operating conditions ensures complete and void-free filling while maintaining reasonable process simplicity.
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 effectively suppresses plating voids even in holes with diameters nearly equal to the insulating layer thickness, enhancing the reliability and durability of the multilayer wiring board under various conditions.
Implementation Method 1
filling in the hole for interlayer connection with an electrolytic plating layer formed by using an electrolytic filling plating solution
Implementation Method 2
creating a hole for interlayer connection by laser
Data Source
AI summary
The present invention is a multilayer wiring board and a method for manufacturing the same, the multilayer wiring board having a hole for interlayer connection penetrating a metal foil and an insulating layer; an overhang of the metal foil formed at an opening of the hole; lower space formed between the overhang and an inside wall of the hole; and interlayer connection in which the hole is filled with electrolytic filling plating layers, wherein the electrolytic filling plating layers are formed as at least two or more layers, the lower space is filled with any electrolytic filling plating layer except for an outermost layer of the two or more layers of electrolytic filling plating layers, and a diameter in the inside of the interlayer connection formed by any electrolytic filling plating layer except for an outermost layer is equal to or larger than a diameter of the opening.