Multilayer Substrate for Power Semiconductor Modules

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Solution Overview

Problem

Conventional power semiconductor modules face challenges in uniform heat transfer due to the bending of ceramic substrates away from heat sinks, leading to non-uniform heat conductive paste thickness and increased electric field concentrations at edges and corners, which affects high voltage isolation and heat dissipation.

Innovation Solution

A multilayer substrate configuration with alternating metal and ceramic layers, where the ceramic layers extend beyond the metal layers, and vias are used to connect metal layers, allowing for even pressure distribution and improved heat dissipation, while also optimizing the electric field distribution across the substrate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single ceramic substrate is used with metallization, then the structure is simple, but the substrate bends away from the heat sink causing non-uniform heat conductive paste thickness

Engineering Contradiction:

Improvesubstrate structureVSAvoidheat conductive paste thickness uniformity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The single ceramic substrate is divided into multiple ceramic layers (first ceramic layer, second ceramic layer) separated by metal layers. This segmentation prevents bending of the entire substrate and allows each layer to maintain uniform contact with the heat sink, ensuring uniform heat conductive paste thickness while reducing overall structural complexity.

Inventive Principle:

Principle #1Segmentation

2Stress or pressure

If mechanical structures are added to distribute downforce uniformly, then pressure distribution improves, but device complexity increases due to limited options from semiconductor chips and bonding wires

Engineering Contradiction:

Improvedownforce distribution uniformityVSAvoidmechanical structure

Core Design Contradiction:

Stress or pressureVSDevice complexity

Solution Approach 1:

The solution moves from adding mechanical structures in the horizontal plane to creating a vertical multilayer structure. The alternating ceramic and metal layers provide inherent pressure distribution through their layered architecture, eliminating the need for additional mechanical components while maintaining uniform downforce distribution across the substrate.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If a thicker ceramic layer is used to increase electrical isolation, then isolation voltage improves, but the sharp rectangular edge geometry still causes electric field concentration

Engineering Contradiction:

Improveelectrical isolationVSAvoidelectric field concentration

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The single thick ceramic layer is segmented into multiple thinner ceramic layers separated by metal layers. This segmentation maintains the total electrical isolation distance while distributing the electric field across multiple interfaces. The metal layers act as field-shielding elements that prevent electric field concentration at edges and corners, thus improving reliability without creating harmful field concentrations.

Inventive Principle:

Principle #1Segmentation

4Loss of energy

If heat conductive paste layer is made very thin to reduce heat transmission resistance, then thermal conductivity improves, but the layer becomes non-uniform due to substrate bending

Engineering Contradiction:

Improveheat transmission resistanceVSAvoidheat conductive paste thickness uniformity

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The heat conduction path is segmented into multiple thin ceramic layers with metal layers in between, eliminating the need for a single thin heat conductive paste layer. Each ceramic layer maintains uniform thickness and direct contact with the heat sink, ensuring consistent thermal conductivity while avoiding the bending-induced non-uniformity that plagues single-layer designs.

Inventive Principle:

Principle #1Segmentation

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 configuration enhances heat transfer efficiency by ensuring uniform pressure and reduces electric field concentrations, enabling better high voltage isolation and heat dissipation in power semiconductor modules.

Implementation Method 1

To improve cooling, the base plate may be pressed against a heat sink... the multilayer substrate includes a first metal layer and a first ceramic layer over the first metal layer... An edge of the first ceramic layer extends beyond an edge of the first metal layer

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

To reduce the heat transmission resistance between the substrate and the heat sink, a layer of heat conductive paste is required

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS8018047B2Power semiconductor module including a multilayer substrate

Publication Date: 2011.09.13 INFINEON TECHNOLOGIES AG

AI summary

A semiconductor module includes a multilayer substrate. The multilayer substrate includes a first metal layer and a first ceramic layer over the first metal layer. An edge of the first ceramic layer extends beyond an edge of the first metal layer. The multilayer substrate includes a second metal layer over the first ceramic layer and a second ceramic layer over the second metal layer. An edge of the second ceramic layer extends beyond an edge of the second metal layer. The multilayer substrate includes a third metal layer over the second ceramic layer.