Schlumberger-Private

PhDProject

Subject: Electronic solder joints microstructure evolution (characterization and modeling) whensubjectedtoharshenvironments.

Nowadays electronic assemblies of oilfield industries are used in harsher and harsher conditionswithusage temperature usually in-between 150°C and 200°C. The main reliability limiting factor of theelectronics is such environment is the solder interconnect system (see left figure). During downholeconditions,theseelectronicsaresubjectedtothermo-mechanicalstressescombiningthermalcyclingatelevated temperature (around 0.90 homologous), high level of shock and the excitation of a broadspectrumofvibrationfrequency.Cyclicfatigueinvolvesthemicrostructuraldamageandfailureofsolderjoints(seerightfigure).

Figure:sectionofapartofaBallGridArray(BGA),atypeofsolderinterconnectsystem.Thediameterofsuch

SnAgCuballs(ontheright)isonlyafewhundredmicrometers(sources:WikipediaandSchlumberger).

This thesis aims to develop statistical damage model(s) based on constitutive relations integratingmicrostructureevolutiontoassesssoldercreepresponseanddamageevolutionofSAC305solderjointssubjected to harsh environment conditions: thermal aging, thermal cycling and shock & vibration. Inaddition,theresultsshouldbeusedtoprovideguidanceonprocessparameteradjustments.

Thethesiswillconsistoftwomainparts:

1. Characterizethegrainstructuresofsolderjointsandanalyzetheeffectofthemicrostructureevolution (recrystallization, grain orientation, size and shape) when subjected to variousthermalcyclingupto185°C(lowcyclefatigue/lowstrainrate)andshock&vibration loading(high cycle fatigue/high strain rate) conditions.Differentmanufacturingprocesses (solderingthermalprofiling)shouldalsobestudied.

2. Develop a microstructure-based constitutive models using statistical approach to predictdamageexperiencedbyelectroniccomponentsolderjoint.

Ideal candidates should have an excellent scientific background, be highly motivated and enjoyexperimentalwork aswell as theory,modeling andprogramming. Theprojectwill enfold its activitiesbetweenthetwopartners:SchlumbergerandEcolePolytechniqueinFrance.

Schlumberger-Private

FINANCEMENT:ThèseCIFREhttp://www.anrt.asso.fr/fr/cifre-7843CONTACTS:Prof.EricCharkalukLaboratoiredeMécaniquedesSolides-CNRS-EcolePolytechnique,91128PalaiseaucedexFranceeric.charkaluk@polytechnique.eduProf.AndreiConstantinescuLaboratoiredeMécaniquedesSolides-CNRS-EcolePolytechnique,91128PalaiseaucedexFranceandrei.constantinescu@polytechnique.eduDr.MaximeVilmayMicroelectronicTechnologyGroupSchlumbergerRiboudProductCenter,92142Clamart–FranceMVilmay@slb.comCleversonSouzaChavesMicroelectronicTechnologyGroupSchlumbergerRiboudProductCenter,92142Clamart–FranceCChaves@slb.com