Wiring Substrate With Roughened Depression Surfaces
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Solution Overview
Problem
There is a challenge in maintaining insulation reliability as wiring density increases in wiring substrates due to ion migration issues, which existing measures have not adequately addressed.
Innovation Solution
A wiring substrate design featuring an insulating layer with projections and depressions where the inner wall and bottom surfaces of the depressions are roughened, and the width of the projection's end face differs from the widths of the metal layers, enhancing adhesion and reducing dendrite formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wiring density is increased to reduce the interval between wiring patterns, then productivity and wiring capacity are improved, but insulation reliability deteriorates due to ion migration
Solution Approach 1:
The patent applies local quality by creating a depression with roughened surfaces specifically at the interface between adjacent wiring patterns, while maintaining smooth surfaces elsewhere. The roughened surface is localized to the depression region where ion migration occurs, providing targeted adhesion enhancement without affecting the overall wiring structure. This localized treatment prevents ion migration at critical interfaces while preserving high wiring density elsewhere.
Solution Approach 2:
The depression is formed in advance during the substrate preparation process, before the wiring patterns are fully assembled. By pre-forming the depression and roughening its surfaces beforehand, the structure is prepared to prevent ion migration before the high-density wiring is in place, addressing the insulation reliability issue proactively rather than reactively.
2Reliability
If etching is used to remove metal residues between wiring patterns, then insulation reliability is improved by preventing ion migration, but device complexity increases due to additional processing steps
Solution Approach 1:
The depression is formed in advance during the substrate preparation process, before the wiring patterns are fully assembled. By pre-forming the depression and roughening its surfaces beforehand, the structure is prepared to prevent ion migration before the high-density wiring is in place, addressing the insulation reliability issue proactively rather than reactively.
Solution Approach 2:
The roughened surface is localized specifically to the depression region at the interface between adjacent wiring patterns, while maintaining smooth surfaces elsewhere. This targeted treatment enhances adhesion precisely where ion migration occurs, providing effective ion migration prevention without requiring extensive additional processing across the entire substrate.
3Reliability
If the width of the projection end face is made different from the metal layer widths, then adhesion is improved and dendrite formation is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs asymmetry by designing the projection end face width to be different from the metal layer widths. This asymmetric configuration creates a stepped structure where the projection end face has one dimension and the metal layers have different dimensions, establishing a geometric relationship that inherently enhances adhesion and prevents dendrite formation through the width difference itself.
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 effectively increases wiring density without compromising insulation reliability, as demonstrated by maintaining high resistance values during accelerated temperature and humidity stress tests, and reduces ion migration by preventing metal deposition at the interface.
Implementation Method 1
An inner wall surface and a bottom surface of a depression around the projection are roughened surfaces
Data Source
AI summary
A wiring substrate includes an insulating layer including a projection and a wiring layer on the projection. The wiring layer includes a first metal layer on an end face of the projection and a second metal layer on the first metal layer. The width of the end face of the projection is different from at least one of the width of the first metal layer and the width of the second metal layer. An inner wall surface and a bottom surface of a depression around the projection are roughened surfaces.