Reliability & Robustness

Simulation, design, implementation and measurement of temperature and degradation phenomena as well as thermal behaviour and EMI of power modules

Open student thesis

Motivation

Real-time monitoring of electrical parameters of power electronic voltage converters allows to increase reliability and to delay the End-of-Life (EoL) of the power semiconductors used. By monitoring the parameters, intervention can be made in the control system to avoid operating points with high load. To achieve this goal, a control infrastructure based on multiple microcontrollers has been built in previous work.

Goals

Microcontrollers from STMicroelectronics (STM32) and dSPACE (MicroLabBox) are used for communication. For the connection of the microcontroller within the existing rapid prototyping environment, an interface for the data exchange from the microcontroller and receiving has to be developed.

Your Tasks
  • Programming and debugging of a custom communication interface in C
  • Implementation of a flash based storage system (micro SD card)
  • Provision of example data (RNG) for data exchange
  • Validation
  • Documentation and creation of user manual
Others

Form, scope and reimbursement of the student assistant position will be arranged in consultation with the supervisors.

Start: immediately

Kontakt: Kevin Muñoz Barón

Conventional power modules consist of a multilayer structure joined together by solder material and use bond wires to connect to the top metallization of the chip (Fig. 1).

Solder joints and bond wires are the weakest links in conventional power modules and limit their reliability. Due to a mismatch of their coefficients of thermal expansion of the components of the module, a temperature induced stress develops, which under cyclic load produces fatigue of these components and ultimately failure of the power module

The goal of this study thesis is to study through simulation the effect of selected parameters on the thermomechanical response of a power module.

Main points (can be weighted on an individual basis)

  • Thermo-Mechanical Analysis
  • Finite Element Simulation

Prerequisites (depending on the actual topic)

  • Experience with Ansys Mechanical (or the willingness to learn it before the study thesis)

PDF

Example of an implemented acquisition circuit

With further advances in electric vehicles, more stringent requirements are being placed on the power electronics. Not only should they be efficient, but also reliable.

Temperature is an important aspect as changes in it directly influence the End-of-Life (EoL) of the device. Measurement is possible through temperature sensitive electrical parameters (TSEPs), but throughout the lifetime of a power device, these parameters can change their value and can affect the temperature acquisition.

In the frame of this work, temperature acquisition through TSEPs with the focus on stability throughout the lifetime of the power device will be investigated. The existing testbench will be the basis for the investigations.

Tasks & Goals

  • Familiarization & literature search (10 %)
  • Design and Simulation (25 %)
    • Implementation of temperature measurement
  • Setup and Measurements (50 %)
    • Setup of the existing test bench
    • Evaluation of the accuracy of the temperature acquisition (thermal imaging camera)
  • Written thesis & presentation (15 %)

Previous knowledge

  • Knowledge of OpAmp based circuits helpful
  • Knowledge of printed circuit board development helpful

Start: immediately

Kontakt: Kevin Muñoz Barón

PDF

Real-time monitoring of electrical parameters of power electronic voltage converters enables an increase of reliability and a delay of the End-of-Life (EoL) of the used power semiconductors. By monitoring the parameters, it is possible to influence the control system in order to avoid operating points with high stress.In order to get closer to the goal of robust power electronics, a sensor hub will be developed and implemented within the scope of this work, which enables data exchange with existing sensor nodes. For this purpose, the necessary hardware and software will be designed based on a capable microcontroller.

Tasks & Goals

  • Familiarization & literature search (10 %)
  • Design and Simulation (35 %)
    • Design of a sensor node based on a STM32 microcontroller
  • Setup and Measurements (40 %)
    • Choice of: Data exchange & storage programming
    • Choice of: Measurement & validation of performance by means of eye diagrams or similar.
  • Written thesis & presentation (15 %)

Previous knowledge

  • Microcontroller knowledge beneficial
  • Knowledge of printed circuit board development helpful

Start: immediately

Kontakt: Kevin Muñoz Barón

PDF

Task

As in many technological areas, the aim in power electronics is to make components smaller, lighter and at the same time more powerful. 3-dimensional circuit carriers such as MID's (Molded Interconnect Devices) have many advantages in this respect. On the one hand they have the potential for further system miniaturization and function integration. On the other hand, the variety of parts in a system can be reduced and heat dissipation can be individually optimized. In addition to thermoplastic-based MIDs, thermoset and ceramic substrate materials have recently been developed and are of interest for power electronics. With smaller power modules and higher power density, however, the demands on packaging and interconnection technology (AVT) are also increasing. Thermal performance is an important criterion for material selection and AVT. The calculation of the transient temperature behavior of the semiconductors for a given power loss profile can be determined e.g. by Zth-curves.

In the context of this work, WBG power semiconductors on novel three-dimensional substrates are to be measured transiently thermally. A part of the work is the conception, design, construction and assembly of test samples with modern AVT-technologies like soldering, silver-sintering or semi-sintering.

The student work is supervised in cooperation between Hahn-Schickard and the ILH.

Individual activities

  • Structure of test specimens
  • Implementation of Zth-examinations
  • Evaluation and summary of the results
  • Documentation of the work

Start: immediately

Contact ILH: Dominik Koch

Contact Hahn-Schickard: Kai Werum

PDF

In power electronics the temperature plays a major role. For example the junction-temperature is a crucial parameter and mandatory for a safe operation. In addition a boundary value for example the heating sink temperature has to be taken into account. To measure these temperatures different measurement methods are used, which all have different advantages and disadvantages.

In this work different sensors should be compared qualitative regarding accuracy, dynamic and complexity. In addition the different sensors should be controlled and read out by a SPI interface and compared at different operations. For this an adapter PCB should be designed, where different sensors can be connected and read out centrally.

Timetable:

  • Familiarization & literature search(10 %)
  • Design and simulation of adapter PCB (20 %)
  • Programming of SPI-interface (20 %)
  • Messung und Evaluierung der einzelnen Sensoren (30 %)
  • Written thesis & presentation (20 %)

Previous knowledge:

  • Circuit/layout design in Altium
  • Experience in practical lab work
  • Ability to work on your own

 

Contact: Kevin Muñoz Barón

Contact: Dominik Koch

PDF

Conventional power modules consist of a multilayer structure joined together by solder material and use bond wires to connect to the top metallization of the chip (Fig. 1).

Solder joints and bond wires are the weakest links in conventional power modules and limit their reliability. Due to a mismatch of their coefficients of thermal expansion of the components of the module, a temperature induced stress develops, which under cyclic load produces fatigue of these components and ultimately failure of the power module

The goal of this study thesis is to study through simulation the effect of selected parameters on the thermomechanical response of a power module.

Main points (can be weighted on an individual basis)

  • Thermo-Mechanical Analysis
  • Finite Element Simulation
  • Experimental Verification

Prerequisites (depending on the actual topic)

  • Experience with Ansys Mechanical (or the willingness to learn it before the study thesis)
  • Experience with microcontrollers (for experimental part)

Kontakt: Kevin Muñoz Barón

PDF

For the operation of power electronic circuits the knowledge of the temperature of the components is an important parameter to control the performance of the cooling system, to detect asymmetric load cases and to detect failures with different time constants.

In many conventional power modules, diodes or resistive temperature sensors are positioned as discrete components next to the power transistor, so that the reaction time of the sensor to a temperature change in the power semiconductor is relatively large (ms…s).

The lateral structure of GaN transistors allows the monolithic integration of sensor and logic circuit parts directly next to the power transistor, which has already led to a significant reduction of the reaction time for temperature measurements in first experiments.

In this thesis a measurement circuit has to be developed, which further reduces the reaction time of the monolithic integrated temperature sensor and thus improves the general failure detection for the power electronic components.

Topics:

  • Temperature protection circuits:
    • Types of protection circuits
    • Simulation possibilities of temperature measurement
    • Possibilities of measured value processing
  • Circuit design of an evaluation circuit
  • Validation of the developed concept

Contact: Jan Hückelheim

PDF

This image shows Benjamin Schoch
M.Sc.

Benjamin Schoch

Research Assistant

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