Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE credits
Schlumberger drilling tools are exposed to very hard loading conditions (shocks, vibrations,
thermal cycling) while performing a job. As these tools are full of electronics, issues can quickly come
from electronics failure. Mechanisms of failure occurring in electronics are very complex but can be
predicted in some cases.
The first part of the thesis describes in which context mechanical engineering applied to
electronics is used in Schlumberger. The different kinds of failure which will be investigated in the
report are presented in this part.
The second part deals with fatigue models used in electronics. From classical methods used in
mechanical engineering to calculate a material fatigue life, fatigue models are adapted and
formulated for special applications.
The third part investigates the issue of capacitor flex-cracking which occurs when boards do not
remain flat during loadings (shocks or thermal cycling). Root causes of this mechanism of failure are
investigated in this part to find key points where improvements have to be made to avoid failure.
The fourth part presents a common failure which deals with Plated Through Holes (PTHs) issues.
A simple model of investigations is established.
The fifth part deals with fatigue life of leadless components (resistors) under thermal cycling.
Even if the failure is revealed during shock tests, the damage is mostly created during the thermal
cycles applied on the board prior to shock. The effect of the size of the component is discussed in this
The last part deals with modal analysis on a given board in order to be able to reduce the impact
and the damage of shocks applied on this board. Simulation and experimental modal analysis are
compared in order to see the influence of certain parameters on the natural frequencies of the
2012. , 31 p.