IGBT Wafer Test Current Ratio Measurement via Emitter Resistor

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Solution Overview

Problem

The existing wafer test method for the current ratio of a power switch cannot accurately measure the current ratio between the main current and detected current due to the positional relationship between the main IGBT and current detecting IGBT on the semiconductor substrate, and it requires a costly dedicated tester to account for the voltage difference caused by the sense resistor.

Innovation Solution

A resistor is connected between the main IGBT emitter terminal and the current detecting IGBT emitter terminal on the probe card, allowing the main IGBT and current detecting IGBT to be turned on simultaneously, enabling the measurement of the current ratio under actual operating conditions using a simple method.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the main IGBT and current detecting IGBT are energized separately for measurement, then the measurement setup is simple, but the measured current ratio does not reflect actual operating conditions due to positional relationship effects on the semiconductor substrate

Engineering Contradiction:

Improvemeasurement setup simplicityVSAvoidcurrent ratio accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent applies preliminary action by pre-connecting a resistor between the emitter terminals of the main IGBT and current detecting IGBT before the wafer test. This preliminary setup ensures that when both IGBTs are energized simultaneously during measurement, the voltage difference caused by sense resistor positioning is already compensated, allowing accurate current ratio measurement under actual operating conditions without requiring complex dedicated testers

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If a dedicated tester is used to account for voltage differences caused by sense resistors, then measurement accuracy is improved, but the cost and device complexity increase significantly

Engineering Contradiction:

Improvecurrent ratio accuracyVSAvoidtester complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent introduces an intermediary element - a resistor connected between the emitter terminals of the main IGBT and current detecting IGBT. This intermediary resistor compensates for the voltage difference caused by the positional relationship of sense resistors on the semiconductor substrate. By using this simple intermediary component instead of a complex dedicated tester, the patent achieves accurate current ratio measurement while keeping the measurement device simple and cost-effective

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If both IGBTs are energized simultaneously, then the current ratio measurement reflects actual operating conditions, but voltage differences due to sense resistor positioning cause measurement errors

Engineering Contradiction:

Improvecurrent ratio accuracy under operating conditionsVSAvoidvoltage difference error

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of voltage differences caused by sense resistor positioning into a beneficial compensation mechanism. By connecting a resistor between the emitter terminals, the voltage difference that would normally cause measurement error is transformed into a compensating voltage drop that cancels out the positioning error. This allows simultaneous energization of both IGBTs to accurately reflect actual operating conditions without measurement errors

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach allows for accurate measurement of the current ratio in a condition similar to actual operation, reducing the need for expensive testers and accounting for the voltage difference, thereby simplifying and cost-effectively measuring the current ratio.

Implementation Method 1

there is provided resistance means that causes an emitter current of the current detecting IGBT to flow through an emitter terminal of the main IGBT

Methodology Applied

Scientific EffectElectrical Resistance: Electrical Resistance

Data Source

PatentUS9541599B2Power switch wafer test method

Publication Date: 2017.01.10 FUJI ELECTRIC CO LTD

AI summary

A wafer test method of a power switch wherein a main IGBT and a current detecting IGBT that detects a current value of the main IGBT are integrally formed on the same semiconductor substrate is such that there is provided resistance means that causes an emitter current of the current detecting IGBT to flow through an emitter terminal of the main IGBT, the main IGBT and current detecting IGBT are energized simultaneously, thereby applying a constant current to a common collector terminal of the main IGBT and current detecting IGBT, and a current ratio (main current/detected current) between a main current of the main IGBT and a detected current of the current detecting IGBT is calculated from the current flowing through the current detecting IGBT, obtained from the voltage across the resistance means, and the constant current.