“Power Module and Power Device” Evaluation Services

"Power Module and Power Device" Evaluation Services

In recent years, as vehicles have become more electrified, the share of electric vehicles (EVs) and hybrid electric vehicles (HEVs) has also increased. Power devices and power modules play a major role in the evolution of EVs and HEVs.

Power devices and modules for vehicles have features of high withstand voltage, fast switching speed and low power loss.

To increase the energy efficiency in EVs and HEVs, wide bandgap semiconductors such as SiC (silicon carbide) and GaN (gallium nitride), which have higher withstand voltage, lower loss, and faster switching than conventional Si (silicon), become used more often.

Ga2O3 (gallium oxide), which is called the third widebandgap semiconductor for power devices, is also attracting attention because of its greater cost advantages and lower theoretical loss than SiC.

WTI offers a variety of evaluation services for the static and switching characteristics of various power devices (Si, SiC, GaN, Ga2O3) and power modules, including diodes, MOSFETs and IGBTs.

In particular, wide bandgap semiconductors (SiC, GaN, Ga2O3) can operate at higher voltages and higher switching speeds than Si semiconductors, so noise problems are more likely to become apparent. Therefore, to make accurate measurements and obtain correct waveforms, it is necessary to understand the material properties of the device and its operating characteristics based on its structure.

Also, front-loading designs such as model-based development are becoming popular as a product development design method, and the power electronics field is not an exception.

WTI is also providing simulation models in collaboration with our partner company MoDeCH Inc.

To determine various parameters for simulation models, accurate measurements of such as internal inductances and switching waveforms of a module are necessary, and performing accurate measurement requires expertise and experiences.

However, only a few companies have the know-how to measure accurately these characteristics even in Japan.

Now the demand for power device and power module evaluation is increasing:

  • Power device and power module evaluation needed for a development on a customer
  • Power device and power module evaluation throughout from characteristics evaluation to reliability evaluation
  • Acquisition of switching waveforms and parameters needed for creating simulation models

WTI can provide solutions to your challenges regarding various power devices and power modules, by collaboration with our partners if necessary.

 

Static characteristics evaluation

  • Evaluation range is up to 2000 V, 400 A.
  • Acquisition of static characteristics of such as power devices (MOSFET, IGBT, SiC, etc.) and power modules are made by using a curve tracer.
Curve tracer Static characteristics of power module (example)
Curve tracer Static characteristics of power module (example)

 

VCE-IC Curve VGE-IC Curve VF-IF Curve
VCE-IC Curve VGE-IC Curve VF-IF Curve
  • Conventionally, low current region measurement and high current region measurement have been performed separately with two curve tracers.
  • Now it is possible to measure automatically at once.

Static characteristics evaluation

Static characteristics evaluation

 

Capacitance measurement between terminals

  • Obtain capacitance values between terminals of such as power devices (MOSFET, IGBT, SiC, etc.) and power modules.
  • Evaluation range is up to 50 V.

Capacitance measurement between terminals

Capacitance between IGBT terminals (example)
Capacitance between IGBT terminals (example)

 

Switching characteristics evaluation

  • Applicable for a product specification up to 1200 V (MOSFET, IGBT, SiC, etc.)
  • We have an experience for power module evaluation up to 650 V, 450 A.
  • Main evaluation items for switching characteristics
    Turn on characteristics (tr, td(on) etc.)
    Turn off characteristics (tf, td(off) etc.)
    Recovery characteristics (trr, Qrr etc.)
  • Acquisition of switching waveforms and parameters needed for simulation model creation, evaluation of inductance inside a product and wirings.
[Auxiliary devices required for power device evaluation]
  Description
Capacitor C The capacitance and withstanding voltage of the Capacitor C are determined by conditions of current and voltage. (cf. 900 V, 1800 μF)
Loading inductance L We have some kinds of inductors from 1 μH to 1 mH.
The appropriate inductance is determined by current.
Wiring between
capacitor and product
Wiring inductance should be minimized because it affects measurement result. In an evaluation of power module, parallel copper bus bars are used for the part of wirings.
Current monitor Current transformer or Rogowski coil is used for a current monitor.
Hot plate Hot plate is used for measurement in high temperature.
It can be used for up to 200 ℃.
Gate driver We basically ask customers to provide them, but you can also use our own drivers.

 

Circuit diagram for switching evaluation 
for a power module (example) Arrangement for switching evaluation 
for a power module (example)
Circuit diagram for switching evaluation
for a power module (example)
Arrangement for switching evaluation
for a power module (example)

 

[Switching evaluation method]
  • Switching evaluation means measuring the switching time, power loss, etc. as specified in the data sheet and so on, while observing the waveform with an oscilloscope.
  • In the measurement of the turn-on and turn-off characteristics of the power module, required input items like pulse width, number of applied pulses, and the L-load value are determined from the voltage and current conditions.
  • If VCE = 300 [V] IC = 100 [A] VGE = ±15 [V] , the required constants are obtained as L load = 200 [μH], pulse width = 13.4 [μs], and number of pulses = 6, using the following equation: Voltage = L load X Current ÷ Pulse width X Pulse number.
    Switching evaluation method
     
  • Reading the value of items provided in a data sheet such as switching time from the waveforms.
    Switching evaluation method
    Definition of turn on, turn off, and switching time

 

Short circuit capability test

The short circuit capability test is conducted until the sample breaks down to check the breaking limit. When destroyed, sparks are generated with a loud noise and pieces of the sample may be scattered around. Therefore, a safe testing environment is required.

We have the environment and the technology to measure the short circuit capability test safely.
Also, to make it safer, we are considering cutting off the power at the moment of destruction to limit the damage of destruction (loud noises, sparks, sample spatters) as much as possible.

[Short circuit capability test method]
  • Measurement conditions
    Evaluation range is up to 850 V.
  • High side
    Apply a gate-to-emitter voltage VGE.
  • Low side
    • Apply a predetermined voltage for the collector-emitter voltage VCE.
    • The test is carried out by increasing the pulse width for each input pulse until the device breaks down.
    • From the waveform before destruction, checking the pulse width and so on as the breakdown limit.

Short circuit capability test

 

Reliability test, structural analysis

  • Various reliability tests, such as high temperature storage, temperature cycle tests, and power cycle tests are performed by us and/or our partners.
  • Structural analysis of products, such as X-ray observation, evaluation environment construction and tool preparation are also available.
Power cycle test environment X ray image of a product structure
(example)
Power cycle test environment X ray image of a product structure
(example)

 

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