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A Review of the Science and Art of Visual Examination in Failure Analysis
Abstract
Visual examination is usually the first step in a failure analysis, but it is not a subject about which much has been written.
In this paper, techniques of visual examination and documentation using digital photography are discussed. The use of different
types of lighting to reveal characteristics of manufactured and fracture surfaces is explored. Practical examples of lighting
setups and photographs obtained using these setups are presented.
... It is considered as a wealth source of information on interpreting the fracture of fibers. Many modern manufacturing technologies require careful identification of the features of fracture surfaces using modern optical techniques for imaging the fracture surface topography and photography (Christie, 2006). The science of fractography is a modern tool for identifying fracture images and providing a valuable library of reference fractographies and case studies. ...
In this article we present an opto‐thermo‐mechanical characterization of isotactic polypropylene monofilament during failure by fracture. The digital photoelasticity, the two‐beam Pluta polarising interference microscope and the computed tomography are used to provide quantitative data and visual models of the fracture regions of isotactic polypropylene fibers suffering failure by fracture at different thermal and mechanical conditions. Birefringence values and the intrinsic stress‐anisotropy are measured at the fracture surface. 3D models of the fracture regions are reconstructed. Photoelastic patterns and two‐beam interferograms are included for illustration.
An automated system capable of visually detecting the two dimensional location of a crack in metal is presented. A peak-detection algorithm is applied to the thermoelastic signal component caused by heat diffusion, obtained from thermoelastic stress analysis using an industrial microbolometer, which is mounted on motion stages, allowing two dimensional tracking of the crack. The system is experimentally validated on coupons under constant amplitude loading, with the crack tip location estimates compared against measurements from an optical microscope. The system is also applied to monitoring crack growth on a geometrically complex section of an aircraft wing under representative flight-spectrum loading.
Detection of the fatigue crack propagation length with high precision is the key to correctly estimating the crack propagation life. In view of the cumbersome testing process, heavy labor intensity and many influences of subjective factors from the operators of the traditional detection methods, the image processing technology based on machine vision is applied to detect the growth state of laboratory standard M (T) specimen with a fatigue crack. First of all, several image de-noising methods are compared to verify that the median filtering method is more suitable for the processing of fatigue crack images in fatigue specimens under laboratory conditions. Secondly, the crack extraction algorithm based on Hough transform and regional growth is determined. Finally, the Zhang thinning algorithm based on the local binary texture feature is improved to refine the image, and the corresponding burr removal algorithm is proposed to refine the images. Compared with the traditional visual inspection method, the image processing technology proposed in this paper can obtain good processing results. The measured crack length error is smaller and smaller with the development of the crack propagation state and can replace the traditional visual inspection method to detect cracks extended status.
Purpose
Pb‐free soldering challenged printed circuit board (PCB) assembly with high temperature. The purpose of this paper is to explain the failure mechanism of printed circuit board (PCB) assembly with solder bubbles of vias to avoid the problems of via‐drilling defects and solder joint failure.
Design/methodology/approach
The failure of PCB vias with solder bubbles was investigated through cross sections and SEM microstructure inspection, TMA measurement, moisture absorption analysis and DSC measurement. The moisture absorption and CTE of FR4 laminate matched with manufacturing requirement to avoid the effects of solder bubbles. The effects of via drilling with a dull drill bit were compared to that with a new drill bit.
Findings
The moisture absorbed inside holes of via plating layers could be exposed to induce solder bubbles during Pb‐free soldering assembly and dull drill bits should be prevented during the drilling process to avoid the no‐bearing drilling effects.
Originality/value
The failure of PCB vias is not only involved in the voiding in solder joints but manufacturing processes of PCB. The paper designs an approach to analyse the properties of PCB materials and the drilling effects of vias to find out the mechanism resulting in solder bubbles of vias. The problem of drill bits should be considered to prevent the moisture absorbed in drilling vias with defects.
Failure of blind via is one of the main causes of an open circuit in printed circuit boards (PCBs). By using macroscopic and
microscopic testing methods and characterization techniques, the failure analysis of the vias on PCB for novel mobile phones
has been systematically carried out. Metallographic inspection shows obvious cracking along the interface of different copper
layers. Micrograph observation and chemical analysis on the grain boundary have definitely identified that inappropriate location
of the vias concerned with circuit design and residue sulfur related to incomplete desmear process predominantly account for
cracking of blind vias, and the occurrence of the cracking is caused by the formation of a brittle Cu
x
S layer. Moreover, the influence of warpage on the reliability of the via was noted. Based on these defaults, improvement
countermeasures and suggestions are addressed in the paper and are of significant value for reference to the safe reliability
and structural integrity of PCB products during manufacturing and services.
Microvia interconnection technology, which mainly includes blind via and buried via, has been put forward to meet the trends of "faster, lighter, reliable" in electronic industry. The technology plays a crucial role in the development of low cost and high density printed circuit board (PCB). However, as the cost for raw materials, like copper, keeps increasing, one defect blind via will lead to not only failure of the whole board but great economic loss as well. The defect causes and mechanisms have been diversified due to the complexity of process, which can be traced back to material property, microvia design, manufacturing process and service environment etc.. This paper focuses on systematic failure analysis of blind vias on PCB for novel mobile phones. A series of modern analytical instruments and methods were used to observe defects of the vias. Meanwhile, focused ion beam (FIB) was adopted, for the first time, both at home and abroad, to obtain the microstructare of copper grains in the cracking interface. Characterization techniques such as FT-IR, TGA and SAM were also performed to inspect thermal stability of the bare boards. The results have shown that obvious cracking occurring along the interface of different plating layers is the main cause of open circuit; and that both sulfur impurity on wall of the vias related to incomplete desmear process and inappropriate location of the vias concerned with circuit design predominantly account for blind vias cracking. It has been revealed that the reason of the cracking generation is concerned with the sulfur segregation and the formation of brittle CuxS (1≤×≤2). Moreover, the influence of warpage on the reliability of the via has also been mentioned. Based on these defaults, improvement countermeasures and suggestions have been addressed in the paper, which are of significant value for reference to the safe reliability and structural integrity of PCB products during manufacturing and services.
The investigative process of failure analysis relies heavily on visual observations, and photography is a key tool for documenting physical evidence and features. This paper reviews photographic principles as applied to failure analysis, and describes the specific techniques needed both in the field and in the laboratory.
Selected References @BULLET F. Hunter and P. Fuqua: Light-Science and Magic: An Introduction to Photographic Lighting Photography in Failure Analysis
- C Brooks
- A Choudhury
- R Mcswain
C. Brooks and A. Choudhury: Metallurgical Failure Analysis, McGraw-Hill, 1993. Selected References @BULLET F. Hunter and P. Fuqua: Light-Science and Magic: An Introduction to Photographic Lighting, Focal Press, Butterworth, 1990. @BULLET R. McSwain: " Photography in Failure Analysis, " Failure Analysis and Prevention, vol. 11, ASM Handbook, ASM International, 2002, pp. 418-28.