Degradation Index for Power Semiconductor Interconnections
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Solution Overview
Problem
Power semiconductor devices face challenges in monitoring the degradation of interconnections and wire-bonds due to thermo-mechanical stress, making it difficult to distinguish between operational condition effects and degradation effects on voltage drops, especially in inaccessible locations like sealed casings, and existing methods require offline testing which disrupts device operations.
Innovation Solution
A method involving measuring voltage drop values under different current and temperature conditions, with calibration data collected at the beginning of the device's life and operational data collected later, to calculate a numerical health index independent of operating temperatures, using a single voltage sensor and without offline calibration, suitable for devices like IGBTs and MOSFETs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage drop is measured to monitor degradation of interconnections, then degradation detection capability is improved, but the measurement becomes strongly dependent on operational conditions (temperature, current) making it difficult to distinguish degradation effects from operational condition effects
Solution Approach 1:
The patent applies parameter changes by measuring voltage drop at multiple different current levels (at least two distinct current values) and using the relationship between these measurements to calculate degradation. By changing the current parameter and observing how voltage drop responds, the system can separate degradation effects from operational condition effects, as the degradation signature appears consistently across different current levels while operational effects vary.
Solution Approach 2:
The system implements feedback by continuously monitoring voltage drop and using it to calculate a degradation index that feeds back into the monitoring system. This allows the system to track degradation progression over time and adjust measurements or interpretations based on accumulated data, improving the ability to distinguish genuine degradation from temporary operational variations.
2Measurement precision
If physical inspection of each device is performed to assess interconnection state, then measurement accuracy is improved, but the method becomes economically unreasonable for large numbers of devices in service
Solution Approach 1:
The patent implements self-service by enabling the power semiconductor device to monitor its own interconnection degradation through built-in voltage sensing capabilities. The device uses its own operational current and voltage measurements to calculate degradation, eliminating the need for external physical inspection equipment or technician intervention. This allows fleet-wide monitoring without the economic burden of physical inspections.
Solution Approach 2:
The system replaces mechanical physical inspection with electrical measurement-based degradation assessment. Instead of physically accessing and inspecting interconnections (which would require device disassembly and direct visual/examination methods), the patent uses electrical voltage and current measurements taken during normal operation to infer degradation state, substituting a non-intrusive electrical method for a mechanical inspection process.
3Reliability
If offline testing methods are used to assess device health, then measurement reliability is improved, but device operations must be interrupted which reduces productivity
Solution Approach 1:
The patent ensures continuity of useful action by enabling degradation monitoring during normal device operation. The voltage drop measurements and degradation calculations are performed using data collected while the device is actively running, without requiring shutdown or interruption of service. This maintains continuous productivity while providing reliable health assessment.
Solution Approach 2:
The system performs preliminary degradation detection and assessment during normal operation, identifying potential issues before they lead to failure. By continuously monitoring voltage drop and calculating degradation indices during service, the system can predict remaining useful life and schedule maintenance proactively, rather than requiring interruptive offline testing to assess device state.
4Measurement precision
If multiple sensors are used to measure voltage drop under different conditions, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies universality by using a single voltage sensor to perform multiple measurement functions. The same sensor measures voltage drop at different current levels and at different times to gather all necessary data for degradation calculation. This multi-functional use of a single sensor achieves the measurement accuracy equivalent to multiple sensors while avoiding the complexity and cost of implementing multiple separate sensing elements.
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
Enables continuous monitoring of the health evolution and quick detection of abnormal situations, providing accurate health and remaining life estimation of power semiconductor devices, even in difficult-to-access locations, without the need for offline calibration or interruption of operations.
Implementation Method 1
wire-bonds and other interconnections (such as metallization and solders) are subject to thermo-mechanical stress, including high thermic changes and vibrations
Implementation Method 2
The degradation of interconnections, wire-bonds and/or metallization manifests in the increase of the electrical resistance (ΔR) in the current path
Implementation Method 3
The electrical resistance is measurable as a growing of voltage drop. The said voltage drops can be gradual and/or abrupt in case of wire-bond failure
Data Source
AI summary
A method to establish a degradation state of electrical connections in a power semiconductor device comprising:measuring at least two voltage drop values under two respective current values for the same temperature value. The two current values are strictly different or the measurements are made under two distinct gate levels of a transistor;saving the measured values as calibration data;monitoring operational conditions of said power semiconductor device;measuring at least two voltage drop values under respective same current values as preceding, and at two respective moments during which the monitored operational conditions corresponding to two respective predefined sets of criteria related to states of operation and to a common temperature;saving the at least two values as operational data;calculating a numerical index in a manner to estimate a degradation state of said power semiconductor device.