Reliability assessment of microelectronic systems: from single crystals to ceramic boards

Research output: ThesisDoctoral Thesis

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Abstract

To satisfy the demand for ever higher up -and download rates in modern smartphones, the mobile communication providers expand the utilized frequency bands for every new generation of mobile communication standards. The wider portfolio of used frequency bands leads to a significantly increased number of frequency filters in modern devices for mobile communications. This, together with the worldwide increased request for e.g. smartphones, led to an excessive demand for precise, efficient and cheap filter components. In this context, Surface Acoustic Wave (SAW) filters are one of today’s leading technologies. A serious challenge going along with these advanced microelectronic parts is the wide range of used material classes and their corresponding differences in thermo-mechanical properties. As a consequence, high stresses may arise after cooling down from production or thermo-cycling during qualification and service. Especially for the used brittle materials always a certain chance for failure exists once a mechanical stress is applied. In this context, the goal of the present work is to gain a deep understanding on the failure and deformation mechanisms occurring in the brittle parts integrated in modern SAW frequency filters. The mechanical properties of strongly anisotropic, piezoelectric single crystals, as well as multilayer ceramic/metal compounds forming the complex 3D electrical connections between functional components, were investigated in depth. Therefore biaxial and uniaxial strength measurements together with fractography are employed to link differences in mechanical strength with their fracture origins. Nanoindentation experiments and in-situ toughness measurements revealed the origins of irreversible deformations and the obtained fracture behaviour, respectively. The gained knowledge was further used to selectively vary crystal orientation and to tailor the orientation of inevitable surface roughness with respect to identified cleavage planes. As a consequence, the mechanical strength of the single crystalline materials could be significantly improved for specific orientations. For the multilayer ceramic substrates of interest the effect of individual features, e.g. vias or electrodes, together with environmental effects were studied and can be utilized for developing new design rules for microelectronic systems. To substantiate the importance of these apparently small details, it is shown for a real multilayer component that a simple change of the electrode’s design can double the mechanical strength of the component delivering the structural integrity required for reliable and cost-efficient production. This point is indispensable for companies to participate in the shark-tank of microelectronic suppliers.
Translated title of the contributionZuverlässigkeitsbewertung von mikroelektronischen Systemen: Von Einkristallen bis zu keramischen Leiterplatten
Original languageEnglish
QualificationDr.mont.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Kiener, Daniel, Assessor A (internal)
  • Bermejo, Raul, Assessor B (internal)
Publication statusPublished - 2018

Bibliographical note

embargoed until null

Keywords

  • single crystals
  • ceramic circuit boards
  • mechanical characterization
  • fractography

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