Failure Analysis

In order to constantly advance the state of the art, it is necessary to know the weak points of current and older generations of power devices. Which fault patterns, are caused by which abnormal operating conditions and which wear marks occur under certain operating conditions? These and other questions require a comprehensive examination of the device, the package and the application.

The object of the failure analysis is a comprehensive description of the current state of a power device and the traceability of failures or deteriorated operating conditions to the application. In addition to a visual inspection for mechanical damage, the investigations include an electrical function validation and finally a section-by-section analysis of the individual device layers.

Ultrasonic examination of a test piece with intact solder layer

Delamination of the solder layer after a certain number of load pulses

Failure states and critically changed operating conditions of components can be attributed to various causes:

Different thermal expansion coefficients within the power device and between the different layers of a power module
Insufficient quality of the packaging process
Unfavourably selected load profiles
Critical switching and overload events
ESD incidents and improper handling of power electronic assemblies
Disregard of component critical environmental conditions

Detection of a bond wire detaching as a result of a power cycling test

Ultimately, failure analysis, i.e. the assessment of the fault pattern and its cause, requires extensive examination of the device and the application on a mechanical, electrical and thermodynamic level. The analysis is supported by various methods:

Optical and ultrasonic microscopy
Bond wire pulling and shear tests
Packaging and semiconductor simulation
Power cycling and dynamic switching and overload tests
Chemical preparation and removal of device layers