Wiring Substrate Via Recess Structure for Peel-Resistant Alignment
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Solution Overview
Problem
Existing multilayer wiring substrates face issues with via conductor peeling and misalignment due to the lack of a stable connection between conductor layers and via conductors, leading to potential open failures and increased electrical resistance.
Innovation Solution
The wiring substrate design includes a conductor layer with a recess that tapers conically towards the via conductor, offset from the through hole opening, and via conductors are formed to extend into these recesses, enhancing adhesion and reducing rotational movement, thereby improving connection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional through hole structure is used without a recess, then the manufacturing process is simpler, but the via conductor peels easily and connection reliability deteriorates
Solution Approach 1:
A recess is formed in the conductor layer before the via conductor is inserted into the through hole. This preliminary structural preparation creates a tapered configuration that guides the via conductor into proper alignment and provides a mechanical interlock feature, preventing peeling and improving connection reliability before the actual connection is made.
Solution Approach 2:
The recess has a tapered shape that narrows toward the bottom of the through hole, creating a curved or conical interface between the conductor layer and the via conductor. This tapered geometry provides a mechanical interlock effect, where the via conductor is physically retained by the recess structure, preventing peeling and enhancing connection stability.
2Manufacturing precision
If the via conductor is directly inserted into a cylindrical through hole, then the manufacturing is easier, but rotational movement occurs causing misalignment
Solution Approach 1:
The recess introduces an asymmetric, tapered geometry into the otherwise symmetric cylindrical through hole structure. This asymmetric tapering creates a unique fit between the via conductor and the conductor layer interface, preventing rotational movement and ensuring precise alignment while maintaining relatively simple manufacturing processes.
3Strength
If the conductor layer surface is flat, then the manufacturing process is simpler, but the via conductor connection is unstable and prone to peeling
Solution Approach 1:
The flat surface of the conductor layer is replaced with a tapered recess structure. This curved or conical surface geometry creates a mechanical interlock with the via conductor, where the tapered walls provide friction and physical retention, significantly enhancing adhesion strength and preventing peeling compared to a flat surface interface.
Data Source
AI summary
A wiring substrate includes a conductor layer, an insulating layer formed on the conductor layer such that the insulating layer is covering the conductor layer, and a via conductor formed in a through hole penetrating through the insulating layer such that the through hole has a first opening on the opposite side with respect to the conductor layer and a second opening facing the conductor layer and that the via conductor is connecting to the conductor layer. The conductor layer has a surface facing the via conductor and having a recess communicating with the through hole such that the recess is smaller than the second opening and has a conical shape tapering toward the opposite side with respect to the via conductor and the recess has the center on the surface of the conductor layer that is offset from the center of the first opening of the through hole.