Dummy Metal Cap Segmentation for Redistribution Line Routing
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Solution Overview
Problem
As semiconductor dies become smaller and more functions are integrated, packaging becomes increasingly difficult due to limited I/O pad density and the risk of solder bridges, especially in fan-in packages, where I/O pads are restricted to the die surface, limiting the number of solder balls that can be packed.
Innovation Solution
The formation of fan-out packages with redistribution lines and dummy metal caps, where dummy through-vias provide anchoring force and stress shielding, allowing for increased I/O pad density by separating dummy metal caps to route redistribution lines through gaps, thereby reducing warpage and improving packaging efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fan-in packaging is used to keep dies small and integrated, then manufacturing cost is reduced and throughput is increased, but the number of I/O pads is limited due to restricted area on die surface
Solution Approach 1:
The patent transitions from fan-in packaging (I/O pads confined to die surface) to fan-out packaging (I/O pads redistributed to larger area on packaging substrate), effectively changing the spatial dimension from 2D die surface to 3D package volume, thereby increasing the number of I/O pads while maintaining small die size
2Quantity of substance
If I/O pad pitch is decreased to increase pad density, then more I/O pads can be packed, but solder bridges may occur
Solution Approach 1:
The patent introduces dummy metal caps that segment and separate adjacent solder balls, physically preventing solder bridges from forming between neighboring pads while allowing the pads themselves to remain closely spaced for high density
Solution Approach 2:
The dummy metal caps act as intermediary structures between adjacent solder balls, providing physical separation and preventing direct contact between solder materials while allowing the underlying I/O pads to maintain high density
3Strength
If dummy metal caps are formed continuously without separation, then stress shielding is provided, but routing of redistribution lines becomes difficult
Solution Approach 1:
The dummy metal cap is segmented into multiple portions with gaps between them, allowing redistribution lines to be routed through these gaps while the remaining portions continue to provide stress shielding to the underlying structure
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 approach enhances packaging efficiency by increasing I/O pad density, reducing warpage, and minimizing stress on redistribution layers, while maintaining the integrity of the package structure.
Implementation Method 1
dummy through-vias provide anchoring force and stress shielding
Implementation Method 2
dummy through-vias provide anchoring force and stress shielding
Data Source
AI summary
A package includes a first dielectric layer, a device die over and attached to the first dielectric layer, an active through-via and a dummy through-via, and an encapsulating material encapsulating the device die, the active through-via, and the dummy through-via. The package further includes a second dielectric layer over and contacting the device die, the active through-via, and the dummy through-via. An active metal cap is over and contacting the second dielectric layer and electrically coupling to the active through-via. The active metal cap overlaps the active through-via. A dummy metal cap is over and contacting the second dielectric layer. The dummy metal cap overlaps the dummy through-via. The dummy metal cap is separated into a first portion and a second portion by a gap. A redistribution line passes through the gap between the first portion and the second portion of the dummy metal cap.