Power-Module Substrate Unit with Solid Diffusion Bonding

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Solution Overview

Problem

Existing power-module substrates face challenges in maintaining accurate positioning of multiple circuit layers due to low rigidity of lead frames and molding die restrictions, leading to difficulties in high integration and radiation performance, especially with temperature fluctuations causing warp deformations.

Innovation Solution

A power-module substrate unit with a ceramic substrate layer, a circuit layer formed by small circuit layers joined via solid diffusion bonding with aluminum and copper layers, and a copper or copper alloy radiation plate, where the thickness, bonding area, and yield stress ratios of the copper layer and radiation plate are optimized to create a symmetrical structure, minimizing internal stresses and preventing warp deformations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple circuit layers are arrayed on an insulated substrate to achieve high integration, then the power module can be downsized with high power density, but temperature fluctuation causes warp deformation that deteriorates mounting yield and radiation performance

Engineering Contradiction:

Improveintegration levelVSAvoidsubstrate warp

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The patent applies asymmetry by configuring the circuit layers and radiation plates in an asymmetric arrangement relative to the insulated substrate. Specifically, multiple circuit layers are arrayed on one surface while radiation plates are positioned on the opposite surface, creating an asymmetric structure that balances thermal expansion stresses and prevents warp deformation during temperature fluctuations.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent employs parameter changes by carefully controlling the thickness, material composition, and bonding strength of the circuit layers and radiation plates. By adjusting these parameters to satisfy specific relational expressions, the substrate maintains dimensional stability under thermal stress while supporting high integration of multiple circuit layers.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If lead frames are used to join and position insulated substrates, then the substrates can be connected, but the low rigidity of lead frames results in poor positioning accuracy

Engineering Contradiction:

Improvesubstrate connectionVSAvoidpositioning accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent extracts the positioning function from the lead frames by using rigid insulated substrates with precisely formed circuit patterns to define component positions. The lead frames are removed from the positioning role, allowing the substrate structure itself to provide accurate positioning through its rigid geometry and patterned circuit layout.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical positioning system based on lead frames with a precision-machined substrate positioning system. The insulated substrates incorporate precise mechanical features such as registration marks, recesses, and circuit pattern geometries that provide accurate positioning without relying on the flexibility of lead frames.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If wiring members with low rigidity are used to determine substrate position, then assembly is simplified, but positioning accuracy deteriorates making high integration difficult

Engineering Contradiction:

Improveassembly complexityVSAvoidposition accuracy

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent applies segmentation by dividing the positioning function into multiple independent features: substrate geometry, circuit pattern layout, and radiation plate positioning. Each segment contributes to the overall positioning accuracy, allowing complex multi-layer assemblies to be precisely positioned through the cumulative effect of multiple segmented positioning features rather than relying on a single rigid component.

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 the reliability of the substrate by preventing deformation, improving radiation performance, and enabling accurate positioning for high integration of circuit layers, while maintaining stability under temperature fluctuations.

Implementation Method 1

a first copper layer joined on the first aluminum layer by solid diffusion bonding

Methodology Applied

Scientific EffectSolid diffusion bonding: Diffusion Welding

Implementation Method 2

the radiation plate is made from copper or copper alloy and joined on the metal layer by solid diffusion bonding

Methodology Applied

Scientific EffectSolid diffusion bonding: Diffusion Welding

Data Source

PatentUS9837363B2Power-module substrate unit and power module

Publication Date: 2017.12.05 MITSUBISHI MATERIALS CORP

AI summary

In a power-module substrate unit, a circuit layer is structured by a plurality of small circuit layers; a ceramic substrate layer is structured by at least one plate; the small circuit layers are formed to have a layered structure having a first aluminum layer bonded on one surface of the ceramic substrate layer and a first copper layer bonded on the first aluminum layer by solid diffusion; a radiation plate is made of copper or copper alloy; the metal layer and the radiation plate are bonded by solid diffusion.