Wiring Substrate Ion Migration Prevention via Intermediary Metal Layer
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Solution Overview
Problem
Increasing wiring density in wiring substrates leads to a decrease in insulation reliability due to ion migration, which existing measures have not adequately addressed.
Innovation Solution
A wiring substrate design featuring a first metal layer on an insulating layer projection with a second metal layer wider than the end face and a third metal layer that covers the side surfaces and peripheral portions of both, using materials that differ to prevent ion migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If wiring density is increased to reduce the interval between wiring patterns, then wiring density is improved, but insulation reliability deteriorates due to ion migration
Solution Approach 1:
A third metal layer is introduced as an intermediary barrier between adjacent wiring patterns. This intermediate layer prevents direct ion migration between wiring patterns by blocking the migration path, thereby maintaining insulation reliability even when wiring density is increased and intervals between patterns are reduced.
Solution Approach 2:
The third metal layer is formed in advance to cover and protect the side surfaces of the first and second metal layers before ion migration can occur. This preliminary protective action prevents ion migration by creating a barrier that blocks the migration path before ions can traverse between adjacent wiring patterns.
2Reliability
If the third metal layer is formed to cover side surfaces and fill gaps, then insulation reliability is improved by preventing ion migration, but device complexity increases
Solution Approach 1:
The third metal layer extends into the vertical dimension by covering the side surfaces of the first and second metal layers and filling the gap between adjacent wiring patterns. This three-dimensional configuration provides comprehensive ion migration prevention by blocking lateral and vertical migration paths, achieving reliable insulation without requiring excessive lateral space.
Data Source
AI summary
A wiring substrate includes a wiring layer on a projection of an insulating layer. The wiring layer includes a first metal layer on an end face of the projection with a peripheral portion of the end face exposed, a second metal layer that is on the first metal layer and wider than the end face, and a third metal layer. The second metal layer includes first and second opposite surfaces with the second surface on the first metal layer with a peripheral portion thereof exposed. The third metal layer covers side surfaces of the first metal layer, and the first surface, the peripheral portion of the second surface, and side surfaces of the second metal layer, and fills in a region where the end face and the peripheral portion of the second surface face each other. The materials of the second and third metal layers are different.