Semiconductor Package Underfill Fillets to Prevent Mold Compound Cracking

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The transfer of stresses and strains from the underfill material, IC die, and/or interposer to the mold compound can cause cracking, reducing the reliability and quality of semiconductor packages.

Innovation Solution

Incorporating shaped fillets of underfill material below the plane of the IC die bottom surface to absorb and distribute stresses and strains, thereby reducing the likelihood of damage to the mold compound.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If underfill material is used to fill gaps between IC die and interposer, then electrical connectivity and mechanical support are improved, but stresses and strains are transferred to mold compound causing cracking

Engineering Contradiction:

Improveelectrical connectivityVSAvoidstress transfer to mold compound

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The underfill material is applied beforehand to create a cushioning layer between the IC die and interposer. This cushioning effect absorbs and distributes thermal expansion stresses and mechanical strains before they can be transferred to the mold compound, preventing cracking while maintaining electrical connectivity through the connection structures.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent modifies the physical and chemical parameters of the underfill material, including its viscosity, curing characteristics, and mechanical properties. By optimizing these parameters, the underfill material achieves the right balance between providing mechanical support for electrical connectivity and absorbing stresses to protect the mold compound from damage.

Inventive Principle:

Principle #35Parameter changes

2Strength

If underfill material surrounds connection structures, then mechanical support is improved, but stresses are transferred to mold compound reducing quality

Engineering Contradiction:

Improvemechanical supportVSAvoidquality of semiconductor package

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The underfill material is selectively applied in specific locations and configurations. It surrounds the connection structures to provide localized mechanical support where needed, while its shaped fillets are positioned to absorb stresses in critical areas. This localized application maintains mechanical strength without unnecessarily transferring stresses to the mold compound in other regions.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent converts the potentially harmful stress transfer into a beneficial stress absorption mechanism. The underfill material is designed to intentionally absorb and distribute stresses that would otherwise damage the mold compound. By embracing this stress absorption capability, the design protects the overall package quality while maintaining necessary mechanical support.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If shaped fillets of underfill material are used, then stress distribution is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvestress distributionVSAvoidcomplexity of underfill structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The underfill material is formed with shaped fillets that have curved, rounded profiles rather than sharp angles. These curved shapes naturally distribute stresses more evenly throughout the underfill material and into the surrounding structures. The smooth transitions in the fillet geometry prevent stress concentration points while maintaining manufacturability through standard dispensing and curing processes.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 quality and reliability of semiconductor packages, increasing yield and expediting qualification, thus reducing costs and improving market share.

Implementation Method 1

The underfill material includes shaped fillets of underfill material that are below a plane corresponding to a bottom surface of the IC die. The shaped fillets of underfill material may reduce a likelihood of stresses and/or strains that damage a mold compound from transferring to the mold compound.

Methodology Applied

Scientific EffectViscoelasticity: Viscoelasticity

Data Source

PatentUS20250364467A1Semiconductor package and method of manufacturing

Publication Date: 2025.11.27 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Some implementations described herein provide a semiconductor package including an integrated circuit die mounted to an interposer using connection structures. An underfill material between the integrated circuit die and the interposer includes shaped fillets that are below a plane corresponding to a bottom surface of the integrated circuit die. The underfill material including the shaped fillets reduces a likelihood of stresses and/or strains that damage a mold compound from transferring to the mold compound from the underfill material, the integrated circuit die, and/or the interposer. In this way, a quality and reliability of the semiconductor package including the underfill material with the shaped fillets is reduced. By improving the quality and reliability of the semiconductor package, a yield of the semiconductor package may increase to decrease a cost of the semiconductor package.