Technical Library | 2024-08-29 18:30:46.0
The mechanical experience of consumption (i.e., feel, softness, and texture) of many foods is intrinsic to their enjoyable consumption, one example being the habit of twisting a sandwich cookie to reveal the cream. Scientifically, sandwich cookies present a paradigmatic model of parallel plate rheometry in which a fluid sample, the cream, is held between two parallel plates, the wafers. When the wafers are counterrotated, the cream deforms, flows, and ultimately fractures, leading to separation of the cookie into two pieces. We introduce Oreology (/Oriːˈɒl@dʒi/), from the Nabisco Oreo for "cookie" and the Greek rheo logia for "flow study," as the study of the flow and fracture of sandwich cookies. Using a laboratory rheometer, we measure failure mechanics of the eponymous Oreo's "creme" and probe the influence of rotation rate, amount of creme, and flavor on the stress–strain curve and postmortem creme distribution. The results typically show adhesive failure, in which nearly all (95%) creme remains on one wafer after failure, and we ascribe this to the production process, as we confirm that the creme-heavy side is uniformly oriented within most of the boxes of Oreos. However, cookies in boxes stored under potentially adverse conditions (higher temperature and humidity) show cohesive failure resulting in the creme dividing between wafer halves after failure. Failure mechanics further classify the creme texture as "mushy." Finally, we introduce and validate the design of an open-source, three-dimensionally printed Oreometer powered by rubber bands and coins for encouraging higher precision home studies to contribute new discoveries to this incipient field of study
Technical Library | 2010-01-13 12:34:10.0
Micro-sectioning (sometimes referred to as cross-sectioning)is a technique, used to characterize materials or to perform a failure mode analysis, for exposing an internal section of a PCB or package. Destructive in nature, cross-sectioning requires encapsulation of the specimen in order to provide support, stability, and protection. Failures that can be investigated through micro-sectional analysis include component defects, thermo-mechanical failures, processing failures related to solder reflow, opens or shorts, voiding and raw material evaluations.
Technical Library | 2024-09-02 21:02:46.0
In conformal coating, there are several mechanisms that cause failure of printed circuit boards (PCBs). In a series of technical bulletins SCH will examine the common failure mechanisms in conformal coating including capillary flow, delamination, cracking, loss of adhesion, dewetting, corrosion, orange peel, pinholes, bubbles and foam.
Technical Library | 2012-12-14 14:28:20.0
This paper examines the potential failure mechanisms that can damage modern lowvoltage CMOS devices and their relationship to electrical testing. Failure mechanisms such as electrostatic discharge (ESD), CMOS latch-up, and transistor gate oxide degradation can occur as a result of electrical over-voltage stress (EOS). In this paper, EOS due to electrical testing is examined and an experiment is conducted using pulsed voltage waveforms corresponding to conditions encountered during in-circuit electrical testing. Experimental results indicate a correlation between amplitude and duration of the pulse waveform and device degradation due to one or more of the failure mechanisms.
Technical Library | 2023-01-23 20:50:05.0
PDC Outline Section 0: Intro Section 1: What is reliability and root cause? Section 2: Overview of failure mechanisms Section 3: Failure analysis techniques – Non-destructive analysis techniques – Destructive analysis – Materials characterization Section 4: Summary and closure
Technical Library | 2009-04-30 18:06:24.0
This presentation surveys the most significant via and via-related laminate failure mechanisms from past to present using data from current induced thermal cycling (CITC) testing, failure analysis, and other sources. The relative life and failure modes of thru vias, buried vias, and microvias (stacked vs. non-stacked) are compared, along with the affect of structure, materials, and peak temperatures on the above. The origin of via-induced laminate failures such as "eyebrow cracks" and Pb free related internal delamination is also explored.
Technical Library | 2021-07-27 14:49:16.0
Conductive anodic filament (CAF) formation, a failure mode in printed wiring boards (PWBs) that are exposed to high humidity and voltage gradients, has caused catastrophic field failures. CAF is an electrochemical migration failure mechanism in PWBs. In this article, we discuss CAF, the factors that enhance it, and the necessary conditions for its occurrence. Published studies are discussed, and the results of historical mean time to failure models are summarized. Potential reasons for CAF enhancement solutions are discussed, and possible directions in which to develop anti-CAF materials are proposed.
Technical Library | 2020-01-09 00:00:30.0
PCBs have a wide range of applications in electronics where they are used for electric signal transfer. For a multilayer build-up, thin copper foils are alternated with epoxy-based prepregs and laminated to each other. Adhesion between copper and epoxy composites is achieved by technologies based on mechanical interlocking or chemical bonding, however for future development, the understanding of failure mechanisms between these materials is of high importance. In literature, various interfacial failures are reported which lead to adhesion loss between copper and epoxy resins. This review aims to give an overview on common coupling technologies and possible failure mechanisms. The information reviewed can in turn lead to the development of new strategies, enhancing the adhesion strength of copper/epoxy joints and, therefore, establishing a basis for future PCB manufacturing.
Technical Library | 2013-01-17 15:34:33.0
The use of an electroless nickel, immersion gold (ENIG) surface finish comes with the inherent potential risk of Black Pad failures that can cause fracture embrittlement at the interface between the solder and the metal pad. As yet, there is no conclusive agreed solution to effectively eliminate Black Pad failures. The case studies presented are intended to add to the understanding of the Black Pad failure mechanism and to identify both the plating and the subsequent assembly processes and conditions that can help to prevent the likelihood of Black Pad occurring.
Technical Library | 2006-11-01 22:37:23.0
Flip Chip Plastic Ball Grid Array (FCPBGA) modules, when subjected to extreme environmental stress testing, may often reveal mechanical and electrical failure mechanisms which may not project to the field application environment. One such test can be the Deep Thermal Cycle (DTC) environmental stress which cycles from -55°C to 125°C. This “hammer” test provides the customer with a level of security for robustness, but does not typically represent conditions which a module is likely to experience during normal handling and operation.
