Composite Package Stiffener Structure for IC Package Warpage

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Solution Overview

Problem

The semiconductor industry faces challenges in reducing warpage of integrated circuit packages due to mismatched coefficients of thermal expansion between package stiffeners and substrates, which can lead to reliability issues and increased manufacturing costs.

Innovation Solution

A package stiffener design incorporating a main body and pillars made of different materials, where the pillars are deformed to secure them within the main body without adhesives, reducing the equivalent coefficient of thermal expansion mismatch and enhancing structural stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a package stiffener is attached to the package substrate, then structural stability is improved, but warpage increases due to mismatched coefficients of thermal expansion

Engineering Contradiction:

Improvestructural stabilityVSAvoidwarpage

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

The package stiffener is constructed as a composite structure with a main body made of a first material and pillars made of a second material with a different coefficient of thermal expansion. This composite design allows the stiffener to maintain structural stability while reducing warpage by distributing thermal stress across materials with complementary expansion properties.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Different regions of the package stiffener are made from different materials - the main body uses a first material while the pillars use a second material. This local differentiation of material properties enables the stiffener to simultaneously provide structural support and compensate for thermal expansion mismatches between the substrate and stiffener.

Inventive Principle:

Principle #3Local quality

2Strength

If adhesives are used to secure pillars in the main body, then structural integrity is improved, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvestructural integrityVSAvoidmanufacturing process complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The pillars are designed to be self-securing through plastic deformation. When inserted into the main body, the pillars deform plastically to lock themselves in place without requiring adhesives or additional fastening steps. This self-service mechanism simplifies manufacturing while maintaining structural integrity.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The chemical bonding mechanism of adhesives is replaced with a mechanical interlocking mechanism based on plastic deformation of the pillars. This substitution eliminates the need for adhesive application processes while achieving equivalent or superior structural integrity through purely mechanical means.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Shape

If more pillars are added to the main body, then warpage reduction is improved, but manufacturing time and cost increase

Engineering Contradiction:

Improvewarpage controlVSAvoidmanufacturing efficiency

Core Design Contradiction:

ShapeVSProductivity

Solution Approach 1:

Rather than filling the entire main body with pillars, the design uses a selective, partial distribution of pillars at strategic locations where they provide maximum warpage compensation. This partial action approach achieves effective warpage control while minimizing the number of pillars and associated manufacturing steps.

Inventive Principle:

Principle #16Partial or excessive 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

This design effectively reduces warpage and improves the reliability of integrated circuit packages by matching thermal expansion coefficients, thereby decreasing the risk of underfill cracking and lowering manufacturing costs by eliminating the need for adhesives.

Implementation Method 1

the pillars are deformed to secure them within the main body without adhesives

Methodology Applied

Scientific EffectPlastic deformation: Plasticity

Implementation Method 2

mismatched coefficients of thermal expansion between package stiffeners and substrates

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

reducing the equivalent coefficient of thermal expansion mismatch

Methodology Applied

Scientific EffectCoefficient of thermal expansion matching: Thermal Expansion

Data Source

PatentUS20240071950A1Integrated Circuit Packages and Methods of Forming the Same

Publication Date: 2024.02.29 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Integrated circuit packages and methods of forming the same are discussed. In an embodiment, a device includes: a package substrate; a semiconductor device attached to the package substrate; an underfill between the semiconductor device and the package substrate; and a package stiffener attached to the package substrate, the package stiffener includes: a main body extending around the semiconductor device and the underfill in a top-down view, the main body having a first coefficient of thermal expansion; and pillars in the main body, each of the pillars extending from a top surface of the main body to a bottom surface of the main body, each of the pillars physically contacting the main body, the pillars having a second coefficient of thermal expansion, the second coefficient of thermal expansion being less than the first coefficient of thermal expansion.