Wiring Substrate Smooth Surface Protection for Void Reduction
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Solution Overview
Problem
The existing wiring substrates face issues with void formation at the boundary surfaces of rough surfaces and via wirings, which can lower the connection reliability due to the irregularities in the surfaces of the high-density wiring layers and insulation layers formed from different materials.
Innovation Solution
A wiring substrate design with a first wiring structure and a second wiring structure, where the second structure has a higher density and includes a protective film with higher migration resistance, covering smooth surfaces and exposing rough surfaces, and is stacked on an insulation layer that covers both the wiring layer and the protective film, reducing void formation and enhancing adhesiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rough surfaces are formed on wiring layers to increase adhesiveness with insulation layers, then adhesiveness is improved, but voids are formed at boundary surfaces with via wirings which lowers connection reliability
Solution Approach 1:
The patent applies different surface qualities to different regions of the wiring layer. Smooth surfaces are formed in regions where via wirings are to be connected to prevent void formation and ensure reliable connections. Rough surfaces are formed in other regions to maintain high adhesiveness with insulation layers. This local differentiation resolves the contradiction by optimizing each region for its specific function.
Solution Approach 2:
The wiring layer surface is segmented into distinct smooth regions and rough regions. The smooth surfaces are specifically positioned at via wiring connection points, while rough surfaces cover other areas. This segmentation allows the structure to simultaneously achieve both high adhesiveness (through rough surfaces) and high connection reliability (through smooth surfaces at critical interfaces).
2Productivity
If high-density wiring layers are stacked on low-density wiring layers to increase wiring density, then wiring density is improved, but voids are formed at boundary surfaces between layers with different materials which lowers connection reliability
Solution Approach 1:
The patent introduces smooth surface regions specifically at the interfaces where via wirings connect to wiring layers in the high-density stack. This local quality control ensures that critical connection interfaces remain void-free even when stacking multiple insulation layers with different materials, thereby maintaining connection reliability while achieving high wiring density.
Data Source
AI summary
A wiring substrate includes a first wiring structure and a second wiring structure having a higher wiring density. The second wiring structure includes a wiring layer formed on a first insulation layer of the first wiring structure. The wiring layer includes a first wiring pattern, the upper surface of which includes smooth and rough surfaces. A protective film, formed from a conductive material having a higher migration resistance than the wiring layer, covers only the smooth surface and includes a smooth upper surface. A second insulation layer stacked on the first insulation layer covers the wiring layer and the protective film. The smooth surface is continuous with and downwardly recessed from the smooth surface to expose a peripheral portion of the protective film. The second insulation layer covers upper, lower, and side surfaces of the peripheral portion.