Heat Conductive Insulating Sheet Curing for Power Modules

Solution Overview

Problem

The existing heat conductive insulating sheets with secondary aggregated boron nitride particles, used in power semiconductor modules, suffer from defects like voids due to insufficient curing during transfer molding, leading to degraded thermal conductivity and electric insulation.

Innovation Solution

Advanced curing of the heat conductive insulating sheet during transfer molding, ensuring a curing degree change of at least 30%, by adjusting the composition and processing conditions, to prevent void formation and enhance thermal and electric insulation properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If secondary aggregated boron nitride particles are used to increase thermal conductivity, then thermal conductivity in the thickness direction is improved, but voids are easily generated during transfer molding leading to degraded thermal conductivity and electric insulation

Engineering Contradiction:

Improvethermal conductivityVSAvoiddefect-free quality

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent applies preliminary action by pre-heating the thermosetting resin to a specific temperature range (80°C to 150°C) before transfer molding. This preliminary heating activates the curing reaction in advance, ensuring that the resin achieves sufficient curing degree during the brief molding process, thereby preventing void formation while maintaining the thermal conductivity benefits of secondary aggregated boron nitride particles

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the temperature parameter of the thermosetting resin from ambient temperature to a pre-heated state (80°C to 150°C). This parameter change accelerates the curing reaction kinetics, allowing the resin to cure adequately during the short molding cycle, thus resolving the contradiction between using porous secondary aggregated particles and preventing void defects

Inventive Principle:

Principle #35Parameter changes

2Temperature

If thermosetting resin is filled with secondary aggregated particles, then thermal conductivity is improved, but the resin does not flow properly during transfer molding causing defects

Engineering Contradiction:

Improvethermal conductivityVSAvoidmolding processability

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by pre-heating the thermosetting resin to a specific temperature range (80°C to 150°C) before transfer molding. This preliminary heating activates the curing reaction in advance, ensuring that the resin achieves sufficient curing degree during the brief molding process, thereby preventing void formation while maintaining the thermal conductivity benefits of secondary aggregated boron nitride particles

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the temperature parameter of the thermosetting resin from ambient temperature to a pre-heated state (80°C to 150°C). This parameter change accelerates the curing reaction kinetics, allowing the resin to cure adequately during the short molding cycle, thus resolving the contradiction between using porous secondary aggregated particles and preventing void defects

Inventive Principle:

Principle #35Parameter changes

3Productivity

If molding pressure is applied for a short period, then productivity is improved, but the resin does not cure sufficiently leading to void formation

Engineering Contradiction:

Improvemolding cycle timeVSAvoidcuring completeness

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies preliminary action by pre-heating the thermosetting resin to a specific temperature range (80°C to 150°C) before transfer molding. This preliminary heating activates the curing reaction in advance, ensuring that the resin achieves sufficient curing degree during the brief molding process, thereby preventing void formation while maintaining the thermal conductivity benefits of secondary aggregated boron nitride particles

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the temperature parameter of the thermosetting resin from ambient temperature to a pre-heated state (80°C to 150°C). This parameter change accelerates the curing reaction kinetics, allowing the resin to cure adequately during the short molding cycle, thus resolving the contradiction between using porous secondary aggregated particles and preventing void defects

Inventive Principle:

Principle #35Parameter changes

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

The method ensures a power module with improved thermal conductivity and electric insulation, minimizing defects and maintaining high performance.

Implementation Method 1

curing of an uncured or semi-cured heat conductive insulating sheet during transfer molding is advanced such that the ratio of change of the curing degree of the heat conductive insulating sheet

Methodology Applied

Scientific EffectCuring: Chemical Bonding

Implementation Method 2

curing of an uncured or semi-cured heat conductive insulating sheet during transfer molding is advanced

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 3

a heat conductive insulating sheet which is manufactured by using a resin composition in which a boron nitride powder that has excellent thermal conductivity and electric insulation ability is contained in a matrix resin

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 4

a boron nitride powder that has excellent thermal conductivity and electric insulation ability

Methodology Applied

Scientific EffectElectrical insulation: Electrical Resistance

Data Source

PatentUS10177068B2Heat conductive insulating sheet, power module, and manufacturing method thereof

Publication Date: 2019.01.08 MITSUBISHI ELECTRIC CORP

AI summary

A method for manufacturing, by a transfer mold method, a power module equipped with a heat conductive insulating sheet in which an inorganic filler including secondary aggregated particles formed by aggregation of primary particles of scaly boron nitride is dispersed in a thermosetting resin, where curing of an uncured or semi-cured heat conductive insulating sheet during transfer molding is advanced under specific conditions. The method for manufacturing a power module equipped with a heat conductive insulating sheet has excellent thermal conductivity and electric insulation ability.