Failure Analysis:
In On-Board Electronics Using 
X-Ray CT by Renault Group

With the development of electric vehicles in particular, the technical advancement anticipated in the automotive industry in the upcoming years is significant and highly challenging. 

With its Guyancourt Technocentre, one of the largest automotive research and development centers in Europe, Renault Group has made innovation one of the secrets to its success.

Vehicles are integrating a multitude of new functionalities, so much so that we now speak of "intelligent vehicles". These new features, such as gesture recognition, virtual assistance, eye-tracking, or attention control, will add to the current progress in accident prevention. These functionalities are made possible by the development of electronics and the integration of numerous sensors in modern vehicles.

Thus, understanding failure mechanisms will ensure quality levels consistent with large-scale manufacturing and distribution.

How Does Renault Group Use X-Ray Micro-Tomography

Comparable to how mechanical components are analyzed, electronic parts analysis follows a similar format. In other words, level 1 analysis—which involves non-destructive methods—is always the first step.

The two main technologies utilized while examining electronic components are radiography and micro-focus X-ray computed tomography. In a non-destructive manner, this enables us to view the interior characteristics of parts and components in order to identify flaws and better comprehend the failure causes. This enables, when permitted, more intrusive studies that target the samples very specifically in order to prevent the destruction of the flaws and the failures of the signatures.

The challenge is to visualize ever-tinier flaws as electronics become more integrated, therefore having technologies with extremely high resolutions is necessary.

4 Challenges Encountered

The EasyTom 160 nano-tomography device, created by RX Solutions for optimum flexibility, was used to conduct the following analyses. 

Here is one of the difficulties with a water sensor that has diodes that are cracked (the other three challenges are listed in the application note at the conclusion of this article).
"The glass cracks could be clearly seen on the high-resolution CT scans. 

Mechanical cutting wouldn't have yielded desired results because the brittle glass could have been cracked as a result of the cuts. 

The cracks are a few microns in size."

Case 1: Water Sensor - Cracked Diodes

It has been proven effective to analyze the microstructure of materials in Li-ion cells with Silicon electrodes using a laboratory microtomograph, both for ex situ analyses on an inert sample and for in situ experiments. Thus, the three-dimensional distribution of silicon in the electrode can be measured using the EasyTom 160, and various degradation phenomena can be seen as they occur.

With this innovation, laboratories and research facilities can significantly speed up their work while continuing to rely on synchrotron sources when the capabilities of the laboratory apparatus are exhausted.
The sensor is comprised of a card that has been covered in dark resin. The component is examined in its entirety, measuring 100x80x60mm.
Failure: Inoperative sensor.

Analysis Challenge: To identify cracks in a very small glass material within a large part.

Root cause: The diode glass cracked mechanically as a result of mechanical stress.

Hypothesis: Due to the PCB's design, the mechanical pressures brought on by the resin (during, for example, its polymerization) may have caused a minor bending of the PCB, which led to the shattering of the two diodes situated in the region most prone to this bending.
Sensor placement within the tomography system.
Despite the branch's 10 cm length, a limited angle capture allowed for a significant magnification to be obtained.

RESULTS on Cracked Diodes

The water detector's incriminated diodes' location
EasyTom 160 -Voxel size: 2µm
Whole part acquisition 100x80x60 mm
Cracking of the diode glass
CT is a cutting-edge technology that has a wide range of uses, including dimensional measurements, assembly inspection, and material analysis.

High-resolution tomography enables internal component inspection in the context of failure analysis for embedded electronics without running the risk of further harm to the problematic component (which could result in damage or loss of elements crucial to the conclusion).
Despite the large size of the part to be analyzed, CT systems like the EasyTom from RX Solutions allow for easy work at multiple scales, going from a global observation of the component to a very high resolution targeted analysis. This makes it a tool of choice for failure analysis in on-board electronics.
Application Note
Failure analysis

X-ray Computed Tomography for failure analysis in on-board electronics Technocentre Renault, Guyancourt, France.

Case 1: Water Sensor - Cracked Diodes
Case 2: Electronic Board - Ball Cracking in BGA
Case 3: Micro-Switch - Contact Pollution
Case 4: Pressure Sensor - Ion Migration
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