SMT Ceramic Capacitor Failure Mechanisms, Isolation Tools, Techniques and Analysis Methods

Fractography of Metals and Plastics

Three major cause of failure had been established for bushings with over 20 years of service namely: seals damaged, leaks at expansion gas chamber and corrosion at bushing tap. In the paper, each root cause of failure is illustrated with true faults occurred while in service. Then detailed analysis is presented, and more important, some corrective measures to prevent bushing explosion had been established. Those include inspection procedures that had been applied to identify and remove from service damaged bushings. Furthermore, those bushings had been disassembled and investigated at bushing repair facilities. Internal inspection confirmed suspected damaged and promote corrective maintenance actions. Results demonstrate that paper insulation is largely unaffected by these root causes if treated at early stages. Most important, the dielectric strength of the main insulation is restored after vacuum treatment and impregnation with new oil. Bushing reliability had been evaluated in laboratory condition with impulse, AC overvoltage and partial discharge measurements, demonstrating that it is possible to restore reliability on aged bushings, if the three main cause of failure are corrected on time.

The switching power has been used in worldwide step by step. DC/DC converter is the core of a switching power. The research of reliability and failure analysis of the DC/DC converters is important to make products reliable and to maintain its performance under different loads. Based on the long-term experience of DC/DC converter failure analysis, two kinds of key failure modes of DC/DC converter which were component failure and assembly failure respectively were studied. In order to prevent the failure occurrence and ensure the reliability of DC/DC converter, several failure analysis case studies were given and the failure mechanisms and possible root causes of failure were investigated. Finally, several failure prevention methods were suggested.

The impeller under consideration is a rotor wheel of a centrifugal compressor, made of 17-4PH martensitic precipitated hardening stainless steel. Its total operating lifetime was estimated to 80,000 h, but it fractured beforehand, 4 days after the scheduled overhaul without any observed pre-symptoms. The important causes of the failure were its working conditions: a moist H2S environment, the applied shaft fitting stress, and the martensitic structure of its material. In the article the post-failure analysis of an impeller is described, explaining the root cause of the impeller failure by means of both experimental and Finite Element Methods (FEM). Sulfide Stress Cracking (SSC) was found to be the primary failure mechanism for the impeller under investigation. Details of the investigations and possible corrective measures to improve performance impellers used under harsh environment conditions are discussed.

The paper reports the investigation on the root cause of source-drain leakage in bulk FinFET devices. While the failing device was readily isolated by nanoprobing technique and the electrical analysis pinpointed the potential defect location inside the Fin channel, the identification of physical root cause went through extreme challenges imposed by the tiny-sized device and the unique FinFET 3D architecture. The initial TEM analysis was misled by the projection of a species in the lamella surface and thus could not explain the electrical data. Careful analysis on the device structure was able to identify the origin of the species and led to the discovery of the actual root cause. This paper will provide the analysis details leading to the findings, and highlight the role of electrical understanding in not only providing guidance for physical analysis but also revealing the true root cause of failure in FinFET devices.

Chapter 9 - Fatigue as a cause of failure of aircraft engine cylinder head

An investigation was conducted to determine the root cause of the premature pavement failure. The premature pavement failure occurred in the form of rutting and alligator cracking. Although the affected portion was repaired by removing and replacing the top 75-mm asphalt concrete (AC), the repaired AC experienced recurring rutting and alligator cracking in a few weeks. Through extensive field and lab testing, it was found that the weak base is the root cause of the premature failure and the brittleness of the AC is secondary. However, both the base and AC were built according to plan and met the current material and field density requirements. It was concluded that density alone for construction quality control is not sufficient, as it was not able to protect against premature failures from occurring. Although there are many different ways to minimize premature failures, an immediate action is to include proof rolling in construction quality control. Proof rolling has been used with success to ensure proper compaction and to locate unstable areas, as the stability is greatly influenced by the degree of densification achieved during compaction.

This case study is to identify and evaluate the root cause for failure of a roller press mill. Cement plant has a heavy crushing operation the roller’s top surface is eroded, which is replaced by hard metal deposition by welding. In manufacturing, most of the steel metals are failing by either fatigue or by hard deposition through welding. In this case, repair welding has been used for several years. But there is no specific welding procedure adapted to repair the large size of the rolling parts as it is very difficult to operate in that situation and constraints of the welding operation. In this connection, the plant was inspected, their log book was verified, and the complete procedure of welding was checked. Further study was done by cutting the small piece of the press roller mill’s material by using diamond abrasive cutter and it was used to prepare the test specimen using wire cut EDM. Further composition of the welding rod and base material were found by SEM study. Subsequently, their hardness values were also measured. From this study, it is concluded that the welding procedure was not followed properly and oxidation took place during the time of weld, because of the large variations of the weldability of the material over the surface of the base metal and also the presence of blue patches in the weld metal during SEM analysis.

A system approach to solving the tribological problems associated with sealing joints implies comprehensive investigation of all the components. To recognize the root cause of any problem and formulate the required performance for extended reliability we have to evaluate any changes in the system as quantitatively as possible. Any measurable parameters, including geometry, density (porosity), hardness distributions, microstructure and grain size changes observed during routine metallurgical analysis could provide evidence of the root cause of failure. In the head-gasket-block sealing system of the internal combustion engine, the EDS evaluation of the chlorine and sulfur distribution through the head gasket flange fracture in conjunction with analysis of the sludge between the head, block and gasket surfaces pointed to the corrosive nature of the gasket flange cracking.This approach is even more useful for the closed tribological system of telescopic hydraulic cylinders or rotary axle shaft oil seals.

Production processes like continuous annealing and continuous galvanizing/galvannealing rely on welding of two strips across their width, for continuous operation. The operational stability of these lines depends highly on the consistency of the welding process. Any failure of weld joint during processing is detrimental to production as the recovery times are very high (~1–3 days). Two instances of similar weld failures having identical chemical composition and dimensions of the strips were investigated to identify the root cause and establish adequate countermeasures. A systematic approach to evaluate weld performance using metallographic examination was carried out. The examinations revealed that poor nugget formation was the root cause of failure. The nugget formation, its orientation and size were also evaluated after carrying out a series of trials with different welding process parameters, and an optimum condition was arrived at. In summary, the weld failure occurred due to insufficient and unbalanced nugget formation which could be rectified by modifying the welding parameters such as current, pressure and speed.

Root cause analysis of the degradation in a unitized regenerative fuel cell

The metallurgy and levels of protective elements in the new P91 and P92 martensitic alloys are quite different to older ferrite pearlite and ferrite bainite steels. This is likely to give problems in the positive identification of failure mechanisms and assessment of the life of superheater tubing. Techniques such as spheroidisation and oxide thickness to assess metal temperatures, or hardness testing and cavitation to estimate the level of creep damage cannot be used with these materials, or are likely to give ambiguous results. These issues are discussed in the paper and were explored in depth in part of a project at the University of Surrey to develop “If-Then” rules for an expert system for power plant failure analysis.The main aim of the proposed expert system is to identify the root causes of such failures in superheater tubing and will encapsulate current knowledge about superheater problems in the form of “If-Then” rules. Root causes of creep failures include furnace design and operation, overestimation of alloy creep properties, inadequate heat treatment and a non-optimum content of strengthening elements.A characteristic of these alloys is that oxidation on the steam side of the tubing can induce premature failures due to the insulating effect of the oxide scales raising tube temperatures. In addition, scale spallation could also increase tube temperatures, as spallation debris may collect in the bottom of tubes, blocking steam flow. Attention is drawn to a potential “runaway affect” in which the tube temperature and rate of oxidation increase with time as the oxide builds up. The root cause of this could either be excessive rates of heat transfer or could be due to inadequate oxidation resistance caused by low levels of protective elements. Methods of identifying which of these is the root cause are discussed.

This paper presents an effective device-level failure analysis (FA) method which uses a high-resolution low-kV Scanning Electron Microscope (SEM) in combination with an integrated state-of-the-art nanomanipulator to locate and characterize single defects in failing CMOS devices. The presented case studies utilize several FA-techniques in combination with SEM-based nanoprobing for nanometer node technologies and demonstrate how these methods are used to investigate the root cause of IC device failures. The methodology represents a highly-efficient physical failure analysis flow for 28nm and larger technology nodes.

Failure mechanisms in motor bearings

This chapter discusses the application of scanning and transmission electron microscopy techniques, X-ray microscopy, as well as scanning probe microscopy for physical failure analysis. With the scaling-down of transistor features and interconnect dimensions and with the introduction of new processes and materials, physical failure analysis becomes more and more an essential task to exclude both yield-limiting process irregularities and reliabilityrelated failures in the semiconductor industry. Advanced imaging tools and techniques are needed to ensure high manufacturing yield and product reliability. Physical failure analysis is an essential task to exclude both yield-limiting process deviations and reliability-related failures in integrated circuit (IC) manufacturing industry. Its goal is to determine the root cause of failures or parameter deviations as a prerequisite for corrective actions. Polysilicon Gate Roughness, control of the transistor gate critical dimension with nanometer accuracy is a top priority task for leading-edge IC manufacturing.