Spring Electrode Tubular Design for Short-Circuit Protection

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Solution Overview

Problem

Press-pack IGBT modules are prone to damage during short circuits due to the concentration of high radio-frequency short-circuit currents at the edge of pressure pads, leading to arcing and potential explosions, which limits miniaturization and increases costs.

Innovation Solution

A spring electrode with a tubular main body that varies in diameter longitudinally, eliminating edge portions to distribute short-circuit currents uniformly across its surface, preventing local concentration and potential dissolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a spring electrode with edge portions is used, then the current carrying capacity is increased, but the short-circuit current concentrates at the edge portions causing dissolution and breakage

Engineering Contradiction:

Improvecurrent carrying capacityVSAvoidresistance to short-circuit current

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The spring electrode is designed with a tubular main body having a curved surface instead of flat surfaces with edges. This curvature eliminates the edge portions where radio-frequency current would concentrate due to the skin effect, thereby preventing local heating and dissolution while maintaining current carrying capacity through the distributed tubular structure

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Reliability

If rugged explosion-proof structures are added, then the safety against short circuit damage is improved, but the device complexity and cost increase

Engineering Contradiction:

Improveexplosion-proof capabilityVSAvoidstructural complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The spring electrode is designed in advance with a tubular main body that inherently prevents short-circuit current concentration through its curved geometry. This preliminary design eliminates the need for additional explosion-proof structures by preventing the root cause of the problem (current concentration at edges) before it can lead to dissolution, arcing, or explosion

Inventive Principle:

Principle #10Preliminary action

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 solution effectively prevents the spring electrode from being dissolved or broken during short circuits, eliminating the need for rugged structures and enabling miniaturization and cost reduction of semiconductor modules.

Implementation Method 1

the Joule heating caused by the short-circuit current dissolves the pressure pad, and breaks the electrical path

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

the short-circuit current is a radio-frequency current, it is feared that the short-circuit current concentrates on an edge portion of the pressure pad due to the skin effect

Methodology Applied

Scientific EffectSkin effect: Skin Effect

Data Source

PatentUS11228128B2Spring electrode

Publication Date: 2022.01.18 MITSUBISHI ELECTRIC CORP

AI summary

The object is to provide a technology that can prevent a spring electrode from being dissolved and broken upon a short circuit in a semiconductor chip. A spring electrode includes a main body. The main body is a tubular conductor, and varies in diameter in a longitudinal direction so that a side surface has bellows. Since the main body of the spring electrode does not include an edge portion, the local concentration of a short-circuit current that flows through the spring electrode upon a short circuit in a semiconductor chip can be reduced. This can prevent the spring electrode from being dissolved and broken.