Wiring Substrate Via Layout for Crack-Resistant Under-Bump Pads
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Solution Overview
Problem
Existing semiconductor packages face challenges in achieving structural stability, reliability, and improved electrical characteristics due to issues with under-bump pads and connections, particularly when subjected to varying pressure distributions from substrate protection layers.
Innovation Solution
The proposed wiring substrate design includes multiple interconnection layers with via portions and wiring patterns that bypass potential cracks in under-bump pads, ensuring stable electrical connections through redundant pathways and reduced pressure-sensitive areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a substrate protection layer is applied to protect under-bump pads, then reliability is improved, but pressure distribution becomes uneven causing cracks
Solution Approach 1:
The under-bump pad is divided into multiple segments (first under-bump pad and second under-bump pad) with wiring patterns connecting them. This segmentation allows the structure to accommodate differential pressure and thermal expansion, preventing crack propagation while maintaining electrical connectivity through multiple pathways.
Solution Approach 2:
The solution extends the connection path from a single-layer vertical connection to a multi-layer three-dimensional structure with via portions connecting different interconnection layers. This dimensional expansion provides redundant connection paths that bypass crack-prone areas, maintaining reliability under pressure variations.
2Reliability
If via portions are positioned to overlap openings in substrate protection layer, then electrical connection is achieved, but structural stability deteriorates due to pressure concentration
Solution Approach 1:
Different regions of the under-bump pad structure are assigned different functions: some areas serve as primary electrical connection points (overlapping openings), while other areas serve as structural support regions (laterally spaced via portions). This local differentiation optimizes both electrical connectivity and mechanical stability without compromising either.
Solution Approach 2:
The wiring pattern and via portion arrangement are designed in advance to provide redundant connection pathways that can compensate for potential failures. The laterally spaced via portions act as cushioning elements that maintain connection stability even when pressure concentrates on the opening-overlapping via portions.
3Reliability
If multiple interconnection layers with via portions are used to bypass cracks, then electrical characteristics are improved, but device complexity increases
Solution Approach 1:
The wiring patterns and via portions serve multiple functions simultaneously: they provide electrical connection, act as structural support, and create redundant pathways for signal transmission. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in device complexity while achieving improved electrical characteristics.
Data Source
AI summary
A wiring substrate may include a first interconnection layer, a second interconnection layer thereon, and a substrate protection layer on a bottom surface of the first interconnection layer. The first interconnection layer may include a first under-bump pad, and a first wiring pattern that is connected to and extends from the first under-bump pad in a first direction. The second interconnection layer may include first and second via portions that are coupled to top surfaces of the first under-bump pad and the first wiring pattern, respectively, and a second wiring pattern that is on and is electrically connected to the first and second via portions. The substrate protection layer may have a first opening exposing a bottom surface of the first under-bump pad. The first via portion may vertically overlap with the first opening, and the second via portion may be horizontally spaced apart from the first opening.