Wiring Substrate Plating Conductor Void Prevention
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Solution Overview
Problem
Existing multilayer wiring substrates face challenges in achieving reliable connections between conductor layers due to limited contact areas and potential voids in the plating conductors, especially in the expansion parts of through holes.
Innovation Solution
A wiring substrate design that includes a first conductor pattern, a second conductor pattern facing it, an insulating layer with a through hole having an expansion part, and a plating conductor that fills the through hole and has a first plating film directly formed on the inner wall and a second plating film formed on top, ensuring a minimum thickness of the first plating film in the expansion part is between 55% to 95% of its thickness in other parts of the through hole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the through hole has an expansion part to increase contact area, then the adhesion strength between plating conductor and conductor pattern is improved, but the plating conductor may form voids in the expansion part
Solution Approach 1:
The patent applies parameter changes by controlling the thickness of the first plating film in the expansion part to be within 55% to 95% of the minimum thickness in other parts. This parameter control prevents excessive thickness variation that would cause voids, while still providing sufficient contact area for adhesion. The specific thickness ratio range resolves the contradiction by ensuring both adequate contact area for strength and proper material distribution to avoid voids.
Solution Approach 2:
The patent applies local quality by creating an expansion part with specific geometric characteristics (larger opening width) while controlling the plating film thickness in that same region. The expansion part has different geometric properties from the rest of the through hole, but the plating film thickness is carefully controlled to maintain quality consistency. This local geometric modification increases contact area without compromising plating integrity.
2Area of stationary object
If the first plating film thickness is increased in the expansion part to improve adhesion, then the contact area is increased, but the plating conductor may become uneven and create voids
Solution Approach 1:
The patent uses parameter changes to control the first plating film thickness ratio between the expansion part and other parts within 55% to 95%. This parameter control allows the expansion part to have sufficient contact area while preventing excessive thickness that would cause unevenness and voids. The specific ratio range balances contact area increase with manufacturing precision.
Solution Approach 2:
The patent applies partial action by providing the expansion part with a controlled amount of additional contact area rather than excessive expansion. The thickness ratio of 55-95% provides sufficient (but not excessive) contact area to improve adhesion while avoiding over-plating that would cause voids and unevenness. This partial enhancement resolves the contradiction between contact area and uniformity.
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 design enhances the adhesion strength and connection reliability between the plating conductors and the conductor patterns by increasing the contact area and minimizing the likelihood of voids, thereby improving the overall performance of the wiring substrate.
Implementation Method 1
a first plating film directly formed on an inner wall of the through hole
Implementation Method 2
a second plating film formed on the first plating film
Data Source
AI summary
A wiring substrate includes a first conductor pattern, a second conductor pattern, an insulating layer interposed between the first and second patterns and having a through hole, and a plating conductor integrally formed with the second pattern and filling the through hole in the insulating layer such that the plating conductor is in contact with the first pattern. The through hole has an expansion part such that an opening width of the through hole on the first pattern side is widened, and the plating conductor includes a first plating film directly formed on inner wall of the through hole and a second plating film formed on the first plating film such that the minimum thickness of the first plating film in the expansion part is in the range of 55% to 95% of the minimum thickness of the first plating film in the through hole other than the expansion part.