Insulating Thermal Sheet Structure for Interconnect Heat Dissipation

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Solution Overview

Problem

Electronic devices face issues with thermal management due to the low thermal conductivity of printed circuit boards and underfill films, which can lead to overheating and mechanical stress from coefficient of thermal expansion differences, and existing thermally conductive sheets are electrically conductive rather than insulating.

Innovation Solution

An electrically-insulating and highly thermal conductive sheet is introduced at the interconnect level, comprising a perforated stack of a thermal conductive material-containing layer sandwiched between ceramic layers, with openings filled with solder or conductive metals, providing a thermally conductive path while maintaining electrical insulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an underfill film is used between the electrical component and the printed circuit board to relax stresses from CTE differences, then the reliability of the electrical connection is improved, but the thermal conductivity between the component and the printed circuit board deteriorates

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidthermal conductivity

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The underfill film is formulated as a composite material containing thermally conductive particles (such as aluminum oxide, aluminum nitride, or boron nitride) dispersed in a resin matrix. This composite structure provides both the mechanical stress relief function of traditional underfill films and enhanced thermal conductivity to enable effective heat dissipation from the electrical component to the printed circuit board.

Inventive Principle:

Principle #40Composite materials

2Device complexity

If the printed circuit board is used as a heat sink to dissipate heat, then the device complexity is reduced, but the thermal conductivity is insufficient compared to dedicated heat sinks

Engineering Contradiction:

Improveheat dissipation structure complexityVSAvoidthermal conductivity

Core Design Contradiction:

Device complexityVSTemperature

Solution Approach 1:

The thermal conductivity parameter of the printed circuit board is enhanced by incorporating thermally conductive materials into the underfill film and optimizing the thermal pathways through the board structure. This allows the PCB to function as an effective heat sink without requiring additional dedicated heat dissipation components, thereby maintaining low device complexity while achieving sufficient thermal management.

Inventive Principle:

Principle #35Parameter changes

3Temperature

If solder bumps are added to the underside of the printed circuit board to dissipate heat, then the thermal conductivity is improved, but the manufacturing complexity increases

Engineering Contradiction:

Improvethermal conductivityVSAvoidmanufacturing complexity

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The solder bumps serve dual functions: providing electrical connections between components and the printed circuit board, and acting as thermal pathways to conduct heat from the component to the board. This multi-functionality eliminates the need for separate thermal management structures, thereby improving thermal conductivity without significantly increasing manufacturing complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 reduces the temperature of electronic devices by up to 4° C without causing excess stress, enhancing performance and reliability by managing heat and stress through the use of materials with matched thermal expansion coefficients.

Implementation Method 1

an electrically-insulating and highly thermal conductive sheet... providing a thermally conductive path while maintaining electrical insulation

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

electrically-insulating and highly thermal conductive sheet... sandwiched between a first ceramic layer and a second ceramic layer

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Implementation Method 3

highly thermal conductive sheet... providing a thermally conductive path

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 4

openings filled with solder or conductive metals, providing a thermally conductive path

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 5

managing heat and stress through the use of materials with matched thermal expansion coefficients

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS20240332121A1Electrically-insulating and highly thermal conductive sheet for electronic devices

Publication Date: 2024.10.03 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

An electronic device in which an electrically-insulating and highly thermal conductive sheet is located at the interconnect level is provided. The presence of the electrically-insulating and highly thermal conductive sheet at the interconnect level provides a significant reduction in the temperature of the electronic device, without causing excess stress in the electronic device. This results in electronic devices that have improved performance and reliability.