Wiring Substrate Reinforcement Vias for Thermal Stress Management
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Solution Overview
Problem
Buildup wiring substrates face issues with cracking and delamination due to thermal stress and external impacts, primarily at the interfaces between reinforcement patterns and insulation layers, which have different coefficients of thermal expansion, leading to reduced rigidity and increased warping.
Innovation Solution
The wiring substrate design incorporates reinforcement vias that extend through insulation layers, connecting reinforcement patterns and providing a more complex stress absorption route, increasing adhesion and reducing cracking by dispersing thermal stress and external impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If reinforcement patterns and reinforcement posts are used to increase rigidity, then warping is reduced, but thermal stress causes cracking and delamination at the interfaces between reinforcement patterns and insulation layers
Solution Approach 1:
The invention transitions from a two-dimensional planar reinforcement structure to a three-dimensional hierarchical structure by having reinforcement via holes extend vertically through multiple insulation layers and connect reinforcement patterns at different levels. This vertical dimensionality addition creates a more complex stress absorption route that disperses thermal stress and external impacts, preventing cracking and delamination while maintaining rigidity enhancement
Solution Approach 2:
The reinforcement via holes are formed to partially extend into the first insulation layer, creating a nested structure where the via holes are embedded within the insulation layers. This nesting allows the reinforcement structure to be integrated within the substrate layers, providing stress absorption and crack prevention while maintaining the overall substrate integrity
2Strength
If reinforcement patterns are continuously extended along each side to connect reinforcement posts, then rigidity increases, but the interface between reinforcement patterns and insulation layers becomes more susceptible to cracking under thermal stress
Solution Approach 1:
The continuous reinforcement pattern is segmented into discrete reinforcement patterns at different levels, connected by reinforcement via holes. This segmentation creates multiple independent reinforcement elements rather than one continuous structure, which disperses the thermal stress concentration that would occur along a continuous interface, thereby reducing cracking susceptibility while maintaining overall rigidity
Solution Approach 2:
The reinforcement structure extends from a two-dimensional continuous pattern into the third vertical dimension through reinforcement via holes that connect patterns at different levels. This dimensional transition creates a distributed three-dimensional reinforcement network that absorbs thermal stress more effectively than a continuous two-dimensional pattern, reducing the harmful effects of thermal expansion differences
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 enhances the substrate's resistance to thermal expansion differences, limits cracking and delamination, and increases the substrate's rigidity and strength, reducing warping and wire breakage.
Implementation Method 1
The reinforcement patterns 203, 206, and 209 (e.g., copper) have a coefficient of thermal expansion that differs from that of the insulation layers 201, 204, and 207 (resin). Stress resulting from the difference in the coefficient of thermal expansion (thermal stress)
Data Source
AI summary
A wiring substrate includes a first reinforcement pattern stacked on a lower surface of a first insulation layer at a peripheral region located at an outer side of a wiring formation region. A first reinforcement via extends through a second insulation layer in the thickness-wise direction and contacts the first reinforcement pattern. A second reinforcement pattern is stacked on a lower surface of the second insulation layer and connected to the first reinforcement pattern by the first reinforcement via. The first reinforcement via includes a top that partially extends into the first insulation layer.