Multi-Underfill Package Assembly for Warpage and Void Reduction

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Solution Overview

Problem

Integrated circuit packages experience warpage due to differences in material properties of package components, which worsens with increasing package size, making it difficult to fill gaps without voids and exacerbating warpage during the curing process of underfills.

Innovation Solution

Employing a combination of Non-Conductive Film (NCF), capillary underfill, and molding underfill with varying properties to fill gaps and reduce warpage, where NCF is applied pre-bonding, capillary underfill fills small gaps, and molding underfill fills larger gaps, with each underfill having distinct thermal expansion coefficients and viscosities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single type of underfill is used to fill gaps in large packages, then the manufacturing process is simple, but warpage increases and void formation occurs

Engineering Contradiction:

Improveunderfill application processVSAvoidgap filling quality

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The underfill application process is segmented into multiple stages using different underfill types. A first underfill (lower viscosity) is applied initially to fill gaps in specific regions, followed by a second underfill (higher viscosity) to fill remaining gaps and provide structural support. This segmentation allows each underfill type to perform its optimal function, preventing voids and reducing warpage while maintaining process manageability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the package receive different underfill types based on their specific requirements. The first underfill is applied to regions requiring gap filling with lower viscosity, while the second underfill is applied to regions requiring higher viscosity for structural stability. This local differentiation of underfill properties ensures optimal filling quality throughout the entire package structure.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If package size increases to provide more functionality, then functionality increases, but warpage becomes more severe

Engineering Contradiction:

Improvepackage functionalityVSAvoidpackage warpage

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The invention changes the physical parameters of the underfill material by using two different viscosity levels. The first underfill has lower viscosity to facilitate flow into gaps in large packages, while the second underfill has higher viscosity to provide structural rigidity. This parameter variation allows the package to maintain stability and reduce warpage even as package size and functionality increase.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The package structure uses a composite underfill system combining two different underfill materials with distinct properties. The first underfill (lower viscosity) and second underfill (higher viscosity) work together in a composite manner, where each material contributes its specific properties to the overall package structure, enabling large packages to maintain dimensional stability while providing enhanced functionality.

Inventive Principle:

Principle #40Composite materials

3Stability of the object's composition

If underfill viscosity is high to reduce warpage, then warpage control improves, but gap filling capability decreases

Engineering Contradiction:

Improvewarpage controlVSAvoidgap filling process

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The lower viscosity first underfill is applied in advance to fill gaps and reach difficult-to-access regions before the higher viscosity second underfill is applied. This preliminary action ensures that gaps are properly filled with the flowable material before the stiffer material is introduced, combining the advantages of both viscosity levels in a sequential manufacturing process.

Inventive Principle:

Principle #10Preliminary action

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

Reduces warpage and void formation in large packages by utilizing underfills with tailored properties to manage stress and fill gaps effectively, ensuring complete filling and minimizing structural deformations.

Implementation Method 1

a first type of underfill and a second type of underfill, which are different from each other, are dispensed underlying a first one and a second one of the plurality of package components

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 2

the curing process of underfills

Methodology Applied

Scientific EffectCuring: Phase Change

Data Source

PatentUS20250357427A1Packages with multiple types of underfill and method forming the same

Publication Date: 2025.11.20 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method includes bonding a first package component over a second package component, dispensing a first underfill between the first package component and the second package component, and bonding a third package component over the second package component. A second underfill is between the third package component and the second package component. The first underfill and the second underfill are different types of underfills.