Wiring Substrate Via Hole Voids via Segmented Insulation
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Solution Overview
Problem
In build-up wiring substrates, the projection of reinforcement material from via hole walls can lead to voids and reduced connection reliability due to differences in processing properties between the reinforcement material and the insulative resin, causing variations in via hole diameter and hindering metal plating and adhesion.
Innovation Solution
A wiring substrate design where a first insulation layer with a reinforcement material is covered by a second insulation layer without reinforcement material, ensuring the reinforcement material is fully covered, and via holes are formed with decreasing diameters to minimize voids and enhance adhesion and connection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a reinforcement material is used in the first insulation layer, then the mechanical strength and stability of the substrate are improved, but the reinforcement material projects from the via hole walls causing voids and reducing connection reliability
Solution Approach 1:
The patent divides the insulation structure into two segments: a first insulation layer containing reinforcement material for mechanical strength, and a second reinforcement-free insulation layer for reliable via hole formation. This segmentation allows each layer to fulfill its specific function without the drawbacks of the other.
Solution Approach 2:
The patent extracts the reinforcement material only from the region where via holes are formed (the second insulation layer), while retaining it in the first insulation layer. This extraction eliminates the projection problem in via holes while preserving the mechanical strength benefits where reinforcement is needed.
2Productivity
If laser beams are used to form via holes in the insulation layer with reinforcement material, then via holes can be formed efficiently, but the reinforcement material projects from the via hole walls due to different processing properties
Solution Approach 1:
The patent segments the insulation layers such that laser via hole formation is performed only in the second reinforcement-free layer, avoiding the processing conflicts between laser ablation and reinforcement material while maintaining efficient via hole formation.
Solution Approach 2:
The first insulation layer with reinforcement material acts as an intermediary layer between the substrate and the second reinforcement-free insulation layer. It provides mechanical support while allowing the second layer to be processed without reinforcement interference.
3Reliability
If the via hole diameter varies due to reinforcement material projection, then metal plating and adhesion are hindered, but removing the reinforcement material compromises substrate stability
Solution Approach 1:
The patent segments the reinforcement material distribution so that it is present in the first insulation layer for substrate stability but absent from the second insulation layer where via holes are formed, ensuring both stability and adhesion reliability.
Solution Approach 2:
The patent applies local quality by having different material compositions in different regions: the first insulation layer has reinforcement material for structural stability, while the second insulation layer is reinforcement-free to ensure uniform via hole formation and metal adhesion.
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 reduces void formation, increases connection reliability by ensuring uniform metal filling and adhesion, and minimizes stress on the substrate, while maintaining a balanced resin thickness for stability.
Implementation Method 1
irradiating the first insulation layer with a laser beam to form a first opening that extends through the reinforcement material and exposes a partial region of an upper surface of the first wiring layer
Implementation Method 2
irradiating the second insulation layer with a laser beam to form a second opening, in which the second opening extends through the second insulation layer located in the first opening and exposes a part of the partial region of the upper surface of the first wiring layer
Data Source
AI summary
A wiring substrate includes a first wiring layer; a first insulation layer including a reinforcement material and a first opening extending through the reinforcement material and exposing a partial region of an upper surface of the first wiring layer, in which an end of the reinforcement material projects in the first opening; a second insulation layer not including a reinforcement material, covering an upper surface of the first insulation layer, a wall surface of the first opening, and a first part of the partial region and an entire surface of the reinforcement material projecting in the first opening, and including a second opening exposing a second part of the partial region; and a second wiring layer including a wiring portion formed on an upper surface of the second insulation layer and a via portion formed in the second opening and connecting the wiring portion to the first wiring layer.