As technology progresses towards smaller electronic packages, thermo-mechanical considerations pose a challenge to package designers. One area of difficulty is the ability to predict the fatigue life of the solder connections. To do this one must be able to accurately model the thermo-mechanical performance of the electronic package. As the solder ball size decreases, it becomes difficult to determine the performance of the package with traditional methods such as the use of strain gages. This is due to the fact that strain gages become limited in size and resolution and lack the ability to measure discreet strain fields as the solder ball size decreases. A solution to the limitations exhibited in strain gages is the use of Moiré interferometry. Moiré interferometry utilizes optical interferometry to measure small, in-plane relative displacements and strains with high sensitivity. Moiré interferometry is a full field technique over the application area, whereas a strain gage gives an average strain for the area encompassed by the gage. This ability to measure full field strains is useful in the analysis of electronic package interconnections; especially when used to measure strains in the solder ball corners, where failure is known to originate. While the improved resolution of the data yielded by the method of Moiré interferometry results in the ability to develop more accurate models, that is not to say the process is simple and without difficulties of it's own. Moiré interferometry is inherently susceptible to error due to experimental and environmental effects; therefore, it is vital to generate a reliable experimental procedure that provides repeatable results. This was achieved in this study by emulating and modifying established procedures to meet our specific application. The developed procedure includes the preparation of the specimen, the replication and transfer of the grids, the use of the PEMI, interpretation of results, and validation of data by finite element analysis using ANSYS software. The data obtained maintained uniformity to the extent required by the scope of this study, and potential sources of error have been identified and should be the subject of further research.

Lors du fonctionnement des packages électroniques, ceux ci sont exposés à diverses sollicitations d'ordres thermiques et mécaniques. De même, la combinaison de ces sources de contraintes constitue l'origine de la quasi majorité des défaillances des packages électroniques. Pour s'assurer de la bonne résistance des packages électroniques, les fabricants pratiquent des tests de fiabilité et des analyses de défaillance avant toute commercialisation. Toutefois, les essais expérimentaux, lors de la phase de conception et de l'élaboration des prototypes, s'avèrent contraignants en termes de temps et de ressources matérielles. En revanche, la simulation numérique à l'aide de la méthode des éléments finis constitue une option alternative en termes de temps et de ressources. Les objectifs dévolus aux travaux de recherche visent à élaborer quatre modèles éléments finis en 3D, validés/calibrés par des essais expérimentaux, intégrant les recommandations JEDEC (1) en vue de : - Procéder à la caractérisation thermique et thermomécanique des packages électroniques ; - Et prédire la durée de vie en fatigue thermique des joints de brasures et ce, en lieu et place de la caractérisation expérimentale normalisée. Or, la mise en œuvre des modèles éléments finis présente certains inconvénients liés aux incertitudes au niveau de la géométrie, des propriétés matériaux, les conditions aux limites ou les charges. Ceux ci ont une influence sur le comportement thermique et thermomécanique des systèmes électroniques. D'où la nécessité de formuler le problème en termes probabilistes et ce, dans le but de mener une étude de fiabilité et d’optimisation des packages électroniques. Pour remédier au temps de calcul énorme généré par les méthodes d’analyse de fiabilité classiques, nous avons développé des méthodologies spécifiques à cette problématique, via des méthodes d’approximation basées sur le krigeage avancé,qui nous ont permis de bâtir un modèle de substitution, qui rallie efficacité et précision. Par conséquent, une analyse de fiabilité a été menée avec exactitude et dans un temps extrêmement court, via les méthodes de simulation Monte Carlo et FORM/SORM, couplées avec le modèle de krigeage avancé. Ensuite, l’analyse de fiabilité a été associée dans le processus d’optimisation, en vue d’améliorer la performance et la fiabilité de la conception structurelle des packages électroniques. A la fin, nous avons procédé à l’applicabilité des dites méthodologies d’analyse de fiabilité aux quatre modèles éléments finis ainsi développés. Il résulte que les analyses de fiabilité menées se sont avérées très utiles pour prédire les effets des incertitudes liées aux propriétés matériaux. De même, l’analyse d’optimisation de fiabilité ainsi réalisée nous a permis d’améliorer la performance et la fiabilité de la conception structurelle des packages électroniques. (1) JEDEC (Joint Electron Device Engineering Council) est un organisme de normalisation des semi-conducteurs. / During operation, electronic packages are exposed to various thermal and mechanical solicitations. These solicitations combined are the source for most of electronic package failures. To ensure electronic packages robustness, manufacturers perform reliability testing and failure analysis prior to any commercialization. However, experimental tests, during design phase and prototypes development, are known to be constraining in terms of time and material resources. This research aims to develop four finite element models in 3D, validated/calibrated by experimental tests, integrating JEDEC recommendations to : - Perform electronic packages thermal and thermomechanical characterization ; - Predict the thermal fatigue life of solder joints in place of the standardized experimental characterization.However, implementation of the finite element model has some disadvantages related to uncertainties at the geometry, material properties, boundary conditions or loads. These uncertainties influence thermal and electronic systems thermomechanical behavior. Hence the need to formulate the problem in probabilistic terms, in order to conduct a reliability study and a electronic packages reliability based design optimization.To remedy the enormous computation time generated by classical reliability analysis methods, we developed methodologies specific to this problem, using approximation methods based on advanced kriging, which allowed us to build a substitution model, combining efficiency and precision. Therefore reliability analysis can be performed accurately and in a very short time with Monte Carlo simulation (MCS) and FORM / SORM methods coupled with the advanced model of kriging. Reliability analysis was associated in the optimization process, to improve the performance and electronic packages structural design reliability. In the end, we applied the reliability analysis methodologies to the four finite element models developed. As a result, reliability analysis proved to be very useful in predicting uncertainties effects related to material properties. Similarly, reliability optimization analysis performed out has enabled us to improve the electronic packages structural design performance and reliability. In the end, we applied the reliability analysis methodologies to the four finite element models developed. As a result, reliability analysis proved to be very useful in predicting uncertainties effects related to material properties. Similarly, reliability optimization analysis performed out has enabled us to improve the electronic packages structural design performance and reliability.

Title from PDF of title page. / Document formatted into pages; contains 87 pages. / Thesis (M.S.M.E.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: As technology progresses towards smaller electronic packages, thermo-mechanical considerations pose a challenge to package designers. One area of difficulty is the ability to predict the fatigue life of the solder connections. To do this one must be able to accurately model the thermo-mechanical performance of the electronic package. As the solder ball size decreases, it becomes difficult to determine the performance of the package with traditional methods such as the use of strain gages. This is due to the fact that strain gages become limited in size and resolution and lack the ability to measure discreet strain fields as the solder ball size decreases. A solution to the limitations exhibited in strain gages is the use of Moiré interferometry. Moiré interferometry utilizes optical interferometry to measure small, in-plane relative displacements and strains with high sensitivity. / ABSTRACT: Moiré interferometry is a full field technique over the application area, whereas a strain gage gives an average strain for the area encompassed by the gage. This ability to measure full field strains is useful in the analysis of electronic package interconnections; especially when used to measure strains in the solder ball corners, where failure is known to originate. While the improved resolution of the data yielded by the method of Moiré interferometry results in the ability to develop more accurate models, that is not to say the process is simple and without difficulties of it's own. Moiré interferometry is inherently susceptible to error due to experimental and environmental effects; therefore, it is vital to generate a reliable experimental procedure that provides repeatable results. This was achieved in this study by emulating and modifying established procedures to meet our specific application. / ABSTRACT: The developed procedure includes the preparation of the specimen, the replication and transfer of the grids, the use of the PEMI, interpretation of results, and validation of data by finite element analysis using ANSYS software. The data obtained maintained uniformity to the extent required by the scope of this study, and potential sources of error have been identified and should be the subject of further research. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.