Ces travaux s’inscrivent dans le cadre du projet GENOME (GEstioN OptiMisée de l’Energie). Ce projet s’intéresse aux solutions de packaging haute-température pour des modules de puissance 40 kW embarqués en aéronautique. Ils s’intègrent dans l’étude de fiabilité des modules de puissance, notamment, les solutions alternatives aux alliages de brasure. De par leurs propriétés physiques, l’argent et l’or-étain ont été sélectionnés comme techniques d’assemblage afin d’étudier et d’évaluer leur fiabilité. Pour ce faire, une méthodologie d’étude de fiabilité des modules de puissance a été définie dans le but de garantir l’exploitabilité des résultats. Ensuite, des analyses destructives et non-destructives ont été réalisées sur des véhicules de tests. Ceux-ci ont été vieillis en cyclages thermiques suivant différents profils afin de comparer leurs influences sur la fiabilité des VTs. L’étude du comportement thermomécanique des assemblages de puissance a été réalisée à l’aide de modélisations par éléments finis. Une méthodologie d’évaluation de la fiabilité des assemblages, basée sur l’étude de la contrainte thermomécanique accumulée dans les couches de joints métalliques, au cours de vieillissements accélérés, est développée. Un deuxième axe devrait permettre de comprendre les modes de défaillance, afin de mettre en lumière les limitations des vieillissements accélérés sévères. / This work is part of “GENOME” project which focuses on high-temperature packaging solutions for electronic power modules. Its mission is to study the reliability of power modules, in particular, the die attach layer. Due to the physical properties of silver and gold-tin, they were selected as die bonds to assess the evolution of their reliability during ageing. In order to achieve this, an appropriate methodology of the power modules reliability has been defined in order to guarantee the results exploitability. Destructive and non-destructive analyzes were carried out on samples aged by different profiles of thermal cycling. These analyzes allowed us to compare the influence of each cycling profile on the reliability of samples. A study of the thermomechanical behavior of power assemblies was carried out using finite element modeling (FEM). A methodology for evaluating the reliability of assemblies during accelerated ageing is developed. A second axis allows us a better understanding of the failure modes and their effects. It also highlights the limitations of severe accelerated ageing. Consequently, the choice of temperature profile is questioned and a limitation of the temperature profile severity must be considered, in order to avoid producing degradations that are not actually found in mission profile.

Abstract Electronic devices are subjected to various usage environments, wherein stresses are induced to components and their interconnections. The level of stress affects the interval of failure occurrences. When the stress level and aging characteristics of sub-material parts are known, the failure occurrence can be predicted. However, the predictions are based on uncertainties and a practical method to help to assess the component interconnection reliability is needed. In this thesis a novel method to utilize the accelerated stress test data for the hazard rate estimates is introduced. The hazard rate expectations of the interconnection elements are presented as interconnection failures in time (i-FIT) figures that can be used as a part of the conventional product reliability estimates. The method utilizes second level reliability test results for a packaging type specific failure occurrence estimates. Furthermore, the results can be used as such in the component packaging reliability estimates. Moreover, a novel method to estimate the interconnection failures in terms of costs is presented. In this novel method the interconnection elements are dealt as cost elements. It is also shown that the costs of the interconnection failures could be very high, if the stress-strength characteristics of the interconnection system are wrongly chosen. The lead-free manufacturing has emphasized the thermal compatibility of the materials of the component, the solder and the Printed Wiring Board. Improper materials for Area Array components will result as excessive component warping during the reflow, as is shown in this thesis. A novel method for estimating the amount of component warping during the lead-free reflow is introduced. In this thesis, a method to predict the second level interconnection hazard rate is introduced. The method utilizes the second level reliability test data in the life time predictions of the component solder joints. The resulted hazard rates can be used as a part of product field performance estimates. Also, the effect of the process variation and the material properties on the lead-free solder joint reliability is introduced. / Tiivistelmä Elektronisen laitteen materiaalien yhteensopivuus ja käyttöympäristö määrittävät sen kokemat rasitukset. Laitteen komponentteihin tai niiden liitoksiin kohdistuvat rasitukset aiheuttavat lopulta laitteen vikaantumisen. Vikaantumisten taajuuteen vaikuttavat paitsi rasituksen taso ja tyyppi, myös laitteen materiaalien ominaisuudet. Todellinen vikaantumistaajuus perustuu kuitenkin muihinkin parametreihin, mistä johtuen vikaantumisennusteet voivat olla epätarkkoja. Tästä syystä käytännölliselle liitosten vikaantumisen arviointimenetelmälle on tarve. Tässä väitöskirjassa esitellään uusi komponenttien juotosliitosten arviointimenetelmä, jonka avulla voidaan muuntaa kiihdytetyn rasitustestauksen tulos vikaantumistaajuusarvioksi laitteen todellisessa käyttöympäristössä. Menelmässä hyödynnetään levytason rasitustestauksen tuloksia komponenttien kotelotyyppikohtaisiin vikaantumisennusteisiin. Menetelmää voidaan käyttää sellaisenaan arvioitaessa komponenttikoteloiden luotettavuutta todellisissa rasitus- tai tuoteympäristöissä. Väitöskirjassa esitellään myös uusi menetelmä vikaantuneiden liitosten kustannusten määrittämiseen, mikä auttaa myös uuden liitosteknologian kokonaiskustannusten arvioimisessa. Lisäksi väitöskirjatyössä osoitetaan, että liitosvikojen aiheuttamat kustannukset voivat olla erittäin korkeita, mikäli juotosliitoksiin kohdistuvat rasitukset ylittävät liitosten suunnitellun kestävyyden. Elektroniikan lyijyttömän valmistamisen myötä komponenttien, juotteen ja piirilevyn materiaalien yhteensopivuus korostuu. Väitöskirjatyössä osoitetaan, että yhteensopimattomien materiaalien käyttäminen komponenteissa voi johtaa komponentin liialliseen taipumaan kuumakonvektiojuottamisen aikana. Lisäksi esitellään menetelmä komponentin taipuman arvioimiseksi lämpötilan funktiona. Tässä väitöskirjassa esitellään uusi menetelmä, jolla voidaan arvioida komponenttien juotosliitosten vikaantumista ja vikaantumisen vaikutusta tuotteiden kokonaiskustannuksiin. Menetelmä perustuu kiihdytetyn rasitustestauksen tuloksiin, joita voidaan käyttää juotosliitosten vikaantumisten arvioimiseen tuotteen todellisissa käyttöolosuhteissa. Lisäksi väitöskirjatyössä on arvioitu juotosmateriaalin ja juotosaluemitoituksen vaikutusta juotosliitosten luotettavuuteen.

Polymer and composite polymer-ceramic nanofibers were prepared by electrospinning process. Solution of 20 wt.% polyvinylidene fluoride (PVDF) in a mixture of dimethyl sulfoxide (DMSO) and acetone in the ratio of 7:3 was chosen as the most suitable precursor. When preparing composite nanofibers, 20 wt.% of barium calcium zirconate titanate (BCZT) or barium titanate (BT) nanoparticles was added to this PVDF solution. Given parameters were defined as the most suitable for the process of electrospinning: voltage of 50 kV, feeding rate of 30 l/min, distance between emitter and collector of 20 cm and needle diameter of 17 G. The effect of polymer molecular weight and the rotation speed of collector was also studied. Various properties of prepared samples were studied: morphology and fiber diameter, phase composition with the use of x-ray diffraction and Fourier transform infrared spectroscopy and also chosen electrical properties. Lower fiber diameters appeared with lower polymer molecular weight and higher rotation speed of the collector. These parameters resulted in higher percentage of the piezoelectric phase as well. The smallest achieved fiber diameter was around 300 nm, the highest percentage of phase was 92 % and the highest piezoelectric constant had a value of 16 pC/N. Composite fibers filled with BT particles showed better properties that the ones filled with BCZT particles.

The content of this thesis is about preparation and processing of lead-free piezoceramic materials with perovskite structure. Potassium sodium niobate (KNN) powder was prepared by solid state reaction (SSR) and liquid phase reaction (sol-gel reaction). The powders were formed by uniaxial and isostatic pressing and further sintered. The density, grain size and morphology were determined on the sintered samples. The powder, synthesised by SSR and sintered in a conventional furnace, was chosen as a standard. The maximum density achieved on samples after optimization of sintering cycle was 93 %TD. The sintering optimization involved a homogenization step at 950 °C, which promotes the correct development of the phase composition and microstructure, followed by sintering at 1120 °C. The same approach and sintering cycle were used for sintering the samples, prepared by sol-gel synthesis. The maximum density of the samples prepared by sol-gel reaction and sintered in a conventional way, was 92 %TD. For further comparison, both of the synthesised powders were sintered using SPS (spark plasma sintering), which increased their final density up to 97 %TD. The approximate value of the piezoelectric coefficient d33 (pC/N) has been measured on selected SSR samples with pure phase composition ((K0,5Na0,5)NbO3). The best measured value of d33 was around 100 pC/N.

Graduation thesis is specialized on dilemma of the integrated circuits with ball grid array. Chapter two describes several types of packages and confrontation of their characteristics. Chapter three considers possibilities of corrections these boards bedded with packages, mounting and demounting of these packages, method of camera control and also inspection of the soldering process. Chapter four attend to practical measuring of thermal profiles and their optimalization.

This work deals with the metal surface wetting problems of molten lead-free solder and monitoring of ongoing processes at the inter-phase interface using the method of evaluation of the height of the molten solder deducted from the video sequences. The work is aimed at evaluating the metal surface wettability, wetting angle determined. Wettability of the metal surface is compared for different types of surface treatments and for different ages of the measured samples. Measurement is performed at the improved workplace, is used to evaluate the newly derived formula for calculating the wetting angle and created program for automatic evaluation of Picture is used to.

This diplomas thesis deals with specific technologies and manufacture of BGA and QFN packages. Also summarizes the most used test methods for assessing the reliability for. Describes the making of equipment for soldering in a nitrogen atmosphere, followed by comparison solder joints of BGA and QFN forming in different atmosphere. Finally, summarizes knowledge about the process of soldering and desoldering lead-free solders for BGA packages, followed by experimental evaluation of the causes of malfunction of repaired samples.

The master thesis analyses electrical conductivity of lead-free solder joints. The test method design for monitoring the electrical conductivity of the soldered joint is described in the practical part. Simulated BGA package with four pin (BGA4) is used for experiments. Tested PCBs are subjected to isothermal aging and current load. During isothermal aging is measured electrical conductivity and optical microscope is used for intermetallic layer (IMC) growth observation. Two types of surface finish (OSP and ENIG) are used for tests and three diameters of solder terminal balls (solder alloy SAC405). The influence of the ratio area connection / solder volume (ratio S / V) on lead-free solder joints conductivity was evaluated.

The doctoral thesis is focused on reliability of lead-free solder SAC 305. Knowledge in the field of fatigue models used in determining the lifetime of solder joints are observed in this thesis. Also such methods of predicting reliability as numerically-analytical methods or reliability experimental tests are mentioned. Practical results of reliability measurement are presented. Experimental data served as the foundation for determining empirical coefficients for the fatigue model based on deformation induced by creep of the solder, which was implemented in the ANSYS environment. Results from different methods were compared and conclusions discussing the suitability of the presented prediction methods are formulated.

Different special brass (e.g. CuZn37Mn3Al2PbSi) and bronze alloys (e.g. CuPb15Sn) are well known for use in oil-hydraulics having in common to be alloyed with lead. The lead content of special brass alloys in this use ranges from 0.1 to 2.0 mass-%. Some bronze alloys provide even much higher contents of lead of 10 to 15 mass-%. Typically, lead is considered for improvement of machinability or castability. Beyond this purpose lead in brass and bronze alloys affects many more properties of manufacturing and application. During the shaping of the parts by means of hot or cold forming often the materials are strained close to their limits. Thanks to lead cracking is prevented during this process. Lead is also of great importance for the improvement of tribological systems. The surfaces of these systems are exposed to friction and wear. Lead is incorporated in the surface layers and supports the tribological system in their running-in process to achieve a steady state of friction and wear. Above all lead is unique because it forms no solid solution with copper or brass and forms no compounds with other typical copper alloying elements. The feasibility assessment of elements in order to substitute lead in brass or bronze alloys has to be done for each alloy and application individually. In oil-hydraulic applications as bushings, slippers or distributor plates, lead-free alloys must fulfil different profiles of requirements, depending on the conditions of manufacturing and application. The requirements do not only include mechanical strength, formability and thermal strength, but also fatigue strength, low friction and high wear resistance and lubricant compatibility. Consequently, the substitution of lead in brass and bronze alloys for application in oil-hydraulics is a challenging task. This does not only apply for the requirements for machining and forming, but particularly for the need of the new alloys to function under wear, friction and corrosion. Examples are given for how these challenges of new lead-free special brass alloys can be met in bushings (machining, friction properties), slippers (forming, strength) and distributor plates (fatigue strength) for axial piston pumps. Further on, new lead-free special brass alloys for contact with environmentally compatible lubricants are presented. All these examples show that there is not the one and only lead-free alloy for applications in oil-hydraulics. In fact, every application requires a different alloy which is composed and processed individually to meet the specific demands.