Dual-Ring Package Structure for CTE Stress and Warpage Control

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Solution Overview

Problem

The existing package structures face challenges with corner/peripheral high co-planarity and high die-to-die underfill stress due to coefficient of thermal expansion mismatches, leading to warpage and delamination issues during thermal cycling, which affect the reliability of semiconductor packages.

Innovation Solution

The implementation of an alongside heat sink structure with a copper ring and an iron-nickel alloy inner ring, attached to the package substrate using adhesives with varying Young's modulus, to manage warpage and stress between the package substrate's corner edge and chip-on-wafer area, enhancing thermal performance and structural integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a single rigid stiffener ring is used to provide mechanical support, then structural integrity is improved, but stress concentration and warpage occur due to CTE mismatch

Engineering Contradiction:

Improvestructural integrityVSAvoidstress concentration

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The single stiffener ring is divided into multiple segmented rings with different material compositions and mechanical properties. Each segment can independently accommodate thermal expansion differences, distributing stress throughout the structure rather than concentrating it at single points, thereby maintaining structural integrity while reducing stress concentration.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The stiffener structure employs composite materials with different coefficients of thermal expansion arranged in specific configurations. These composite rings are designed to match the CTE characteristics of adjacent package components, reducing thermal mismatch stress while providing the necessary mechanical support and structural strength.

Inventive Principle:

Principle #40Composite materials

2Strength

If adhesive with high Young's modulus is used to attach rings, then bonding strength is improved, but warpage control deteriorates due to rigid constraint

Engineering Contradiction:

Improvebonding strengthVSAvoidwarpage

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

Adhesives with different Young's modulus values are selectively applied to different ring segments based on their specific functional requirements. Areas requiring strong bonding use high-modulus adhesives, while areas needing warpage compliance use lower-modulus adhesives, creating a gradient of mechanical properties that simultaneously achieves bonding strength and warpage control.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The Young's modulus of the adhesive layer is varied as a controllable parameter across different locations in the package structure. By adjusting this mechanical parameter, the adhesive can transition between rigid constraint (for bonding strength) and flexible compliance (for warpage management), optimizing both bonding performance and dimensional stability.

Inventive Principle:

Principle #35Parameter changes

3Stress or pressure

If multiple rings with different materials are used to manage CTE mismatch, then stress distribution is improved, but device complexity increases

Engineering Contradiction:

Improvestress distributionVSAvoidstructure complexity

Core Design Contradiction:

Stress or pressureVSDevice complexity

Solution Approach 1:

Multiple rings with different material properties are nested concentrically around the package substrate, with each ring serving a specific stress-management function. This nested configuration allows complex multi-material stress distribution while maintaining a compact, organized structure that is easier to manufacture and assemble compared to distributed multi-component arrangements.

Inventive Principle:

Principle #7Nested doll (Nesting)

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 solution effectively mitigates warpage and stress-related issues, improving the reliability and thermal performance of semiconductor packages by providing collaborative warpage control and CTE mismatch stress management.

Implementation Method 1

coefficient of thermal expansion mismatches, leading to warpage and delamination issues during thermal cycling

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

coefficient of thermal expansion mismatches, leading to warpage and delamination issues

Methodology Applied

Scientific EffectCTE mismatch stress: Thermal Expansion

Implementation Method 3

attached to the package substrate using adhesives with varying Young's modulus

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS20250006572A1Package structure including ring structure and methods of forming the same

Publication Date: 2025.01.02 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A package structure includes a package substrate, a semiconductor die module on the package substrate, a first adhesive and a second adhesive on the package structure, wherein the second adhesive is between the first adhesive and the semiconductor die module, and a ring structure on the package substrate around the semiconductor die module, wherein the ring structure includes an outer ring attached to the package substrate by the first adhesive, and an inner ring between the semiconductor die module and the outer ring and attached to the package substrate by the second adhesive.