MODELING THE PHYSICS OF FAILURE FOR ELECTRONIC PACKAGING COMPONENTS SUBJECTED TO THERMAL AND MECHANICAL LOADING

This dissertation presents three separate studies that examined electronic components using numerical modeling approaches. The use of modeling techniques provided a deeper understanding of the physical phenomena that contribute to the formation of cracks inside ceramic capacitors, damage inside plated through holes, and to dynamic fracture of MEMS structures. The modeling yielded numerical substantiations for previously proposed theoretical explanations. Multi-Layer Ceramic Capacitors (MLCCs) mounted with stiffer lead-free solder have shown greater tolerance than tin-lead solder for single cycle board bending loads with low strain rates. In contrast, flexible terminations have greater tolerance than stiffer standard terminations under the same conditions. It has been proposed that residual stresses in the capacitor account for this disparity. These stresses have been attributed to the higher solidification temperature of lead free solders coupled with the CTE mismatch between the board and the capacitor ceramic. This research indicated that the higher solidification temperatures affected the residual stresses. Inaccuracies in predicting barrel failures of plated through holes are suspected to arise from neglecting the effects of the reflow process on the copper material. This research used thermo mechanical analysis (TMA) results to model the damage in the copper above the glass transition temperature (Tg) during reflow. Damage estimates from the hysteresis plots were used to improve failure predictions. Modeling was performed to examine the theory that brittle fracture in MEMS structures is not affected by strain rates. Numerical modeling was conducted to predict the probability of dynamic failure caused by shock loads. The models used a quasi-static global gravitational load to predict the probability of brittle fracture. The research presented in this dissertation explored drivers for failure mechanisms in flex cracking of capacitors, barrel failures in plated through holes, and dynamic fracture of MEMS. The studies used numerical modeling to provide new insights into underlying physical phenomena. In each case, theoretical explanations were examined where difficult geometries and complex material properties made it difficult or impossible to obtain direct measurements

Solder Joint Reliability Of Flip Chip BGA Package

Daya tahan hubungan bebola pateri merupakan satu kriteria keboleharapan yang penting dalam pempakejan elektronik moden. The integrity of ball and bump solder joints is a major reliability concern in modern micro electronic packages

The Threat of Plant Toxins and Bioterrorism: A Review

The intentional use of highly pathogenic microorganisms, such as bacteria, viruses or their toxins, to spread mass-scale diseases that destabilize populations (with motivations of religious or ideological belief, monetary implications, or political decisions) is defined as bioterrorism. Although the success of a bioterrorism attack is not very realistic due to technical constraints, it is not unlikely and the threat of such an attack is higher than ever before. It is now a fact that the capability to create panic has allured terrorists for the use of biological agents (BAs) to cause terror attacks. In the era of biotechnology and nanotechnology, accessibility in terms of price and availability has spread fast, with new sophisticated BAs often being produced and used. Moreover, there are some BAs that are becoming increasingly important, such as toxins produced by bacteria (e.g., Botulinum toxin, BTX), or Enterotoxyn type B, also known as Staphylococcal Enterotoxin B (SEB)) and extractions from plants. The most increasing records are with regards to the extraction / production of ricin, abrin, modeccin, viscumin and volkensin, which are the most lethal plant toxins known to humans, even in low amounts. Moreover, ricin was also developed as an aerosol biological warfare agent (BWA) by the US and its allies during World War II, but was never used. Nowadays, there are increasing records that show how easy it can be to extract plant toxins and transform them into biological weapon agents (BWAs), regardless of the scale of the group of individuals

HIGH ACCELERATIONS PRODUCED THROUGH SECONDARY IMPACT AND ITS EFFECT ON RELIABILITY OF PRINTED WIRING ASSEMBLIES

The focus of this thesis is the investigation of extremely high accelerations through secondary impact and its effect on reliability of printed wiring assemblies. The test equipment consists of a commercially available drop system and a commercially available attachment termed a Dual Mass Shock Amplifier (DMSA), which extends the impact acceleration range to as much as 30,000 Gs by utilizing secondary impact dynamics. Further secondary impacts between the test vehicle and fixture are intentionally generated in simulation and tested experimentally to imitate board 'slap' phenomena in product assemblies, and to generate even further amplification of the acceleration at various locations on the test specimen. In this thesis a detailed description of the test equipment and modeling techniques are provided. Model complexity ranges from simple analytic closed-form rigid-body mechanics to detailed nonlinear dynamic finite element analysis. The effects of different equipment design parameters (table mass, spring stiffness, table clearance) are investigated through parametric modeling. The effects of contact parameters (constraint enforcement algorithms, stiffness, damping) on model accuracy are explored. Test fixtures for high shock accelerations are discussed and used for board level reliability testing of printed wire assemblies containing WLCSP49s and MEMS microphones

Computational methods in Flipchip assembly.

Flip chip technology, in the book edited by Lau (Lau, 1995) is defined as placing a chip to the substrate by flipping over the chip so that the I/O area of the chip is facing the substrate. By flipping over the chip, the interconnection between the chip and the substrate are achieved by conductive "bumps" placed directly in between the die surface and the substrate. Therefore, the whole chip surface can be utilized for active interconnections and at the same time, eliminates the need for wire bonding

Computational Methods In Flip Chip Assembly.

Flip chip technology, in the book edited by Lau (Lau, 1995) is defined as placing a chip to the substrate by flipping over the chip so that the I/O area of the chip is facing the substrate. By flipping over the chip, the interconnection between the chip and the substrate are achieved by conductive "bumps" placed directly in between the die surface and the substrate. Therefore, the whole chip surface can be utilized for active interconnections and at the same time, eliminates the need for wire bonding

Response and Durability of Large Radius of Gyration Structures Subjected to Biaxial Vibration

Multiaxial vibration tests were conducted using an electrodynamic shaker capable of controlled vibration in six degrees of freedom. The test specimen consisted of six large inductors insertion mounted on a printed wiring board. Average damage accumulation rate was measured for random excitation in-plane, out-of-plane, and both directions simultaneously. Under simultaneous biaxial excitation, the damage rate was found to be 2.2 times larger than the sum of the in-plane and out-of-plane rates. The conclusion was that multiple-step single-degree-of-freedom testing can significantly overestimate the durability of some structures in a multiaxial environment. To examine the mechanics behind this phenomenon, the response of a simple rod structure was analyzed with the finite element method. Axial vibrations, which produce negligible stress on their own, were found to contribute significant additional stress when combined with transverse vibration. This additional stress contribution was found to be highly dependent on the frequency ratio and phase relationship between the two participating axes

Improved micro-contact resistance model that considers material deformation, electron transport and thin film characteristics

This paper reports on an improved analytic model forpredicting micro-contact resistance needed for designing microelectro-mechanical systems (MEMS) switches. The originalmodel had two primary considerations: 1) contact materialdeformation (i.e. elastic, plastic, or elastic-plastic) and 2) effectivecontact area radius. The model also assumed that individual aspotswere close together and that their interactions weredependent on each other which led to using the single effective aspotcontact area model. This single effective area model wasused to determine specific electron transport regions (i.e. ballistic,quasi-ballistic, or diffusive) by comparing the effective radius andthe mean free path of an electron. Using this model required thatmicro-switch contact materials be deposited, during devicefabrication, with processes ensuring low surface roughness values(i.e. sputtered films). Sputtered thin film electric contacts,however, do not behave like bulk materials and the effects of thinfilm contacts and spreading resistance must be considered. Theimproved micro-contact resistance model accounts for the twoprimary considerations above, as well as, using thin film,sputtered, electric contact