Package-on-Package Structure with Thermal Interface Material

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Solution Overview

Problem

The semiconductor industry faces challenges in achieving smaller form factors, higher performance, and lower power consumption as demand increases for miniaturization, higher speed, and greater bandwidth, which existing packaging techniques struggle to address effectively.

Innovation Solution

A package-on-package (PoP) structure is implemented, where two semiconductor device packages are bonded together using a thermal interfacing material (TIM) and a heat spreader to enhance thermal performance and reduce warpage, with the TIM dissipating heat from the bottom package to the top package and the heat spreader improving stiffness and thermal dissipation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If conventional packaging techniques are used, then manufacturing simplicity is maintained, but thermal performance and structural rigidity deteriorate

Engineering Contradiction:

Improvethermal performanceVSAvoidpackaging structure complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The patent implements a package-on-package structure where a first device package is embedded within a second device package. The first package is formed in a cavity of the second package, creating a nested configuration that improves thermal performance and structural rigidity while maintaining compact form factor. This nesting approach allows heat dissipation pathways to be integrated within the package structure itself.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent employs composite material structures including molding compound layers, substrate materials, and thermal interface materials combined in a multi-layer configuration. The second package includes a first molding compound, substrate, and second molding compound, creating a composite structure that optimizes both thermal management and mechanical stability without requiring overly complex packaging techniques.

Inventive Principle:

Principle #40Composite materials

2Volume of moving object

If device size is reduced for miniaturization, then form factor is improved, but heat dissipation capability deteriorates

Engineering Contradiction:

Improvedevice form factorVSAvoidheat dissipation capability

Core Design Contradiction:

Volume of moving objectVSTemperature

Solution Approach 1:

The patent transitions from planar heat dissipation to three-dimensional heat management by stacking packages vertically. The first device package is positioned within a cavity of the second package, creating vertical heat dissipation pathways. This dimensional change allows efficient heat management in a compact footprint, addressing miniaturization requirements while maintaining thermal performance.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

By nesting the first package within the second package's cavity, the design achieves compact volume utilization. The nested configuration allows heat to dissipate through multiple pathways including through the substrate and molding compounds, maintaining effective heat dissipation capability despite the reduced overall device form factor.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Productivity

If multiple semiconductor wafers are stacked to reduce form factor, then integration density is improved, but warpage and reliability issues worsen

Engineering Contradiction:

Improveintegration densityVSAvoidwarpage resistance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies local quality by creating a cavity in the second package specifically designed to accommodate the first package. This localized structural modification provides mechanical support and constraint at the critical interface between stacked packages, reducing warpage while maintaining high integration density. The cavity configuration allows for controlled thermal and mechanical properties at the bonding interface.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of bonding packages together and then managing warpage, the patent inverts the approach by pre-forming a cavity in the second package before stacking. This inversion allows the first package to be received in a pre-prepared recess, providing inherent mechanical support that prevents warpage from developing during and after the bonding process, thereby improving reliability.

Inventive Principle:

Principle #13The other way round (Inversion)

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 results in improved thermal performance, reliability, and reduced warpage, enabling more efficient heat dissipation and increased structural rigidity, thus addressing the limitations of existing packaging techniques.

Implementation Method 1

the TIM dissipating heat from the bottom package to the top package

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

the heat spreader improving stiffness and thermal dissipation

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS9881908B2Integrated fan-out package on package structure and methods of forming same

Publication Date: 2018.01.30 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

An embodiment package includes a first package; a thermal interface material (TIM) contacting a top surface of the first package, and a second package bonded to the first package. The second package includes a first semiconductor die, and the TIM contacts a bottom surface of the first semiconductor die. The package further includes a heat spreader disposed on an opposing surface of the second package as the first package.