Dummy Bonding Pads for Uniform Underfill in Fan-Out Packaging

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Solution Overview

Problem

Interfaces between fan-out wafer level packages (FOWLP) and underfill material portions are subjected to mechanical and thermal stresses, leading to crack formation in the underfill material and potentially inducing additional cracks in semiconductor dies and other package components.

Innovation Solution

The use of dummy metal bonding structures and dummy solder material portions enhances the capillary force during underfill material application, ensuring uniform distribution and reducing void formation in the underfill material, thereby mitigating stress-induced cracks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional underfill application methods are used without dummy structures, then the manufacturing process is simpler, but the underfill material distribution is non-uniform and voids form

Engineering Contradiction:

Improveuniformity of underfill material distributionVSAvoidcomplexity of bonding structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Dummy metal bonding structures are created as copies of actual bonding structures, positioned in regions where no semiconductor die is present. These dummy structures replicate the geometric and material properties of real bonding pads, providing consistent capillary action for underfill material flow without requiring complex process modifications.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The bonding structure is made non-uniform by adding dummy metal bonding structures only in specific regions where semiconductor dies are absent. This local modification ensures uniform underfill distribution at critical interfaces while maintaining simplicity in other areas, applying complexity only where needed to solve the specific problem.

Inventive Principle:

Principle #3Local quality

2Reliability

If traditional underfill application methods are used without dummy structures, then the manufacturing process is simpler, but cracks form in the underfill material due to stress concentration

Engineering Contradiction:

Improvecrack resistance of underfill materialVSAvoidcomplexity of bonding structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Dummy metal bonding structures replicate the stress-distributing geometry of actual bonding structures in regions where semiconductor dies are absent. This copying approach ensures that stress is evenly distributed across the underfill material during thermal cycling and mechanical loading, preventing crack formation without requiring fundamental changes to the bonding architecture.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

Dummy metal bonding structures are positioned in advance in regions where semiconductor dies will not be placed. These structures serve as preemptive stress-distribution elements that prevent future crack formation in the underfill material, cushioning against thermal and mechanical stresses before they can cause damage.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Manufacturing precision

If traditional underfill application methods are used without dummy structures, then fewer materials are used, but voids form in the underfill material reducing package quality

Engineering Contradiction:

Improvevoid formation control in underfill materialVSAvoidamount of metal bonding material

Core Design Contradiction:

Manufacturing precisionVSQuantity of substance

Solution Approach 1:

Dummy metal bonding structures are created as simplified copies in non-die regions, using the same metal layers and geometric patterns as actual bonding structures. This copying ensures consistent underfill flow and void prevention without requiring excessive material, as the dummy structures are limited to specific regions where dies are absent.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

Metal bonding material is added locally only in regions where semiconductor dies are not present. This localized addition of material ensures uniform underfill distribution and prevents voids at critical interfaces, while minimizing the total quantity of metal material used by avoiding unnecessary structures in die regions.

Inventive Principle:

Principle #3Local quality

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 improves the uniformity of underfill material distribution, reduces void formation, and enhances the reliability of semiconductor die packaging by minimizing stress-induced cracks in the underfill material and associated package components.

Implementation Method 1

Methodology Applied

Scientific EffectCapillary force: Capillary Action

Data Source

PatentUS12232307B2Dummy metal bonding pads for underfill application in semiconductor die packaging and methods of forming the same

Publication Date: 2025.02.18 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A fan-out package includes a redistribution structure having redistribution-side bonding structures, a plurality of semiconductor dies including a respective set of die-side bonding structures that is attached to a respective subset of the redistribution-side bonding structures through a respective set of solder material portions, and an underfill material portion laterally surrounding the redistribution-side bonding structures and the die-side bonding structures of the plurality of semiconductor dies. A subset of the redistribution-side bonding structures is not bonded to any of the die-side bonding structures of the plurality of semiconductor dies and is laterally surrounded by the underfill material portion, and is used to provide uniform distribution of the underfill material during formation of the underfill material portion.