Failure Analysis Blog

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Ever see a picture of an ant’s eye blown up so large you can count the small facets that make it compound? How about a picture of a strand of human hair blown up so you can see the ridges on it? These are all examples of Electron Microscopy. While electron microscope images do make really cool computer backgrounds, there are quite a few practical uses for them.

Electronic packages undergo extensive failure analysis processing when they are found to be defective. The results of these findings can echo all the way back to the design stage of the integrated circuit itself. The meticulousness and care with which failure analysis procedures are carried out are reflected in the extremely low failure rates of the electronic devices we use every day. Most of the time when one of our electronics malfunctions, it is due to a mechanical failure even though the complexities are thousands of times greater in the heart of the chip.

All failure analysis procedures invariably end with prying open the chip in one way or another to obtain visual confirmation of the error. This procedure is known as decapsulation or decapping and is accomplished through a variety of means. While failure analysis techniques generally fall into destructive and nondestructive testing, the end result is almost always the same. Without being able to see the defect for yourself, it's impossible to be sure of the cause. While techniques like acoustic microscopy and emission microscopy can provide pointers to what went wrong, decapsulation is extremely important in order to draw any firm conclusions about the sample.

Electronic circuits come in all shapes and sizes and degrees of sophistication. They can range from being part of a cluster of supercomputers to being present in your air-conditioner remote control. In all uses great and small, they play a key role in enabling the functionality we take for granted every day. Fundamental to all uses, is the concept of the integrated circuit. What used to take several rooms to accomplish can now be done on a microscopic scale. It’s hardly an exaggeration to put the development of the integrated circuit on the same platform as the steam engine. Over the years, they have become smaller and smaller while at the same time packing ever higher densities. This has enabled miniaturization on a scale never before imagined.

An integrated circuit is susceptible to multiple points of failure. Each step along the process of design, manufacture, transportation and storage introduces possibilities for error. Whether we are talking about excessive humidity, dust, detachment of the die, or electrical failure, each malfunction requires extensive testing in order to determine the cause. Failure analysis engineers subject a defective electronic package to an extensive battery of tests to ascertain the cause of failure. In order to do this, they have to ensure that the chip is not substantially altered between tests so that the results of subsequent ones are not skewed. This leads to the importance of what is known as Nondestructive Testing or NDT. These procedures preserve the chip for further analysis.

As we've seen before, fluorescent imaging is an important tool in the analysis of integrated circuits. It is a nondestructive procedure that maintains the integrity of the chip and provides us with valuable information about its composition and the different substances present in it. Other innovative uses have involved stimulated emission depletion that attempts to increase the resolution of the image by using lasers to light up the center of a fluorescent spot. The physics of fluorescence is easy to understand. It relies on the spontaneous emission of photons as electrons in higher orbitals revert back to their normal state. Of course, not all materials exhibit proper fluorescent properties.

The technology involved in microscopy continued to evolve as the science of quantum mechanics progressed. During the time when we were bumping up against the limits of optical microscopy due to the wavelength of visible light, the notion of electrons having a de Broglie wavelength hadn’t been developed. As a result, scientists were using workarounds such as ultraviolet light to improve the resolution of images. When it became apparent however that particles such as electrons could also behave like waves act the sub atomic scale, these phenomena were quickly adapted for use in microscopy. As a result, scanning electron microscopy techniques as well as related procedures such as Transmission Electron Microscopy or TEM were developed.

EMMI or Emission Microscopy analysis is the process of detecting electromagnetic emissions from electronic circuits that are malfunctioning. Every object emits light – whether it is electronic or not. Electronic circuits by virtue of operating at a higher temperature than normal, give off more than usual. If you use a laptop, just try placing your hand outside the fan vent and see how hot it gets. Electronic circuits are always designed with heatsinks in mind to absorb excess infrared radiation. While heat is a nuisance, it can also give us valuable information about the inner workings of an integrated circuit. Many things can go wrong necessitating failure analysis. Emission microscopy provides an easy and noninvasive way of detecting certain types of errors.

Failure analysis engineers are never satisfied in their quest to obtain more precise measurements of a given sample of an integrated circuit. As we have seen before, the scanning electron microscope represents a tremendous improvement over traditional optical-based instruments due to working around the limitations of the wavelength of visible light itself. Other procedures such as field emission microscopy and emission depletion serve as additional methods to obtain close-up images. One other technique is known as Atomic Force Microscopy and which represents a major advance in imaging allowing us to obtain resolutions of up to fractions of a nanometer. Apart from this, AFM has several advantages over a traditional electron microscope.

With all of the various failure analysis processes such as infrared thermography, scanning electron microscopy, field emission microscopy and acoustics, it's important to develop a formalized process for isolating the root cause of failure. So far we have examined all of these various technologies in detail. In today's article we look at the overall flowchart of the failure analysis process and its goal in improving the manufacturing, transportation, and storage processes that ultimately led to the failure in the first place. This requires us to carefully select issues that have a chance to be resolved by root cause analysis. The end result is a Pareto ranking of the various defects leading to a structured approach.

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