Package Substrate Dummy Via Layout for Underfill Crack Suppression

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Solution Overview

Problem

Interfaces between a fan-out wafer level package (FOWLP) and an underfill material portion experience mechanical stress during handling and use, leading to cracks in the underfill material and other package components, which can induce further damage.

Innovation Solution

Incorporation of dummy vias on the package substrate, particularly on the BGA side of the dielectric layer, aligned with the edge of a stiffener ring, to mitigate crack formation by enhancing the substrate's structural integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a stiffener ring is formed on the package substrate to provide rigidity, then the mechanical strength and crack resistance are improved, but the device complexity and manufacturing steps increase

Engineering Contradiction:

Improvemechanical strengthVSAvoiddevice complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

Dummy vias are formed in advance during the substrate fabrication process before the stiffener ring is attached. This preliminary action prepares the substrate to distribute mechanical stresses before the actual mechanical loading occurs, allowing the stiffener ring to be simpler in design while still achieving crack suppression at critical interfaces.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The dummy vias act as intermediary stress-distributing elements between the stiffener ring and the underlying substrate structure. They mediate the mechanical stress transfer, preventing stress concentration at the stiffener ring edges that would otherwise cause cracks in the underfill material and semiconductor die.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If dummy vias are added to the package substrate to inhibit crack formation, then the reliability is improved, but the manufacturing precision requirements increase

Engineering Contradiction:

ImprovereliabilityVSAvoidmanufacturing precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

Dummy vias are strategically placed only at specific high-stress locations such as near the edges of the stiffener ring and at corners, rather than uniformly across the entire substrate. This localized approach provides crack suppression where most needed while minimizing additional manufacturing complexity and precision requirements in low-stress areas.

Inventive Principle:

Principle #3Local quality

3Strength

If the substrate rigidity is increased to prevent cracks, then the mechanical robustness is improved, but the stress distribution capability deteriorates

Engineering Contradiction:

Improvemechanical robustnessVSAvoidstress distribution

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The substrate is segmented into regions with different mechanical properties through the strategic placement of dummy vias. The areas with dummy vias have enhanced stress distribution capability, while other areas maintain the base substrate rigidity. This segmentation allows the substrate to simultaneously provide overall mechanical robustness and localized stress relief at critical interfaces.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS20250279374A1Semiconductor package including package substrate with dummy via and method of forming the same

Publication Date: 2025.09.04 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A semiconductor package may include a package substrate including a dummy via on a first side of the package substrate, an interposer module on a second side of the package substrate opposite the first side of the package substrate, and a stiffener ring on the second side of the package substrate and including an edge that is substantially aligned with the dummy via.