Posted by Fred Koenig on Mar 10th 2022
Failure Analysis and Microscopes
When failure happens within any branch of the manufacturing industry, it is standard to begin failure analysis immediately. Failure analysis is when an investigation takes place to determine the cause of the failure, usually intending to take corrective action in fixing the problem and mitigating against any further malfunctions. This is essential for any industrial department or company to prevent future asset and product failures and ensure the protection against potentially dangerous risks to people and the environment.
What reason do industries conduct failure analysis testing?
The failure analysis process provides several excellent benefits, including safety-related outcomes, legal and financial.
- Understanding the root cause of a failure. Understanding the root cause of a failure is frequently the fundamental part of failure analysis. In-depth data collection is made to ascertain whether the failure is due to manufacturing, material defect, or misuse.
- Preventing asset or future failures. Once the cause of the failure has been thoroughly investigated and determined, corrective actions can be taken to avoid recurrence.
- Future product and process improvement. When understanding the failure is accomplished, manufacturing processes and product design can be improved, preventing the problem from happening again and preventing costly replacements, ensuring customer safety, and protecting the company's reputation.
Forensic Engineering Failure Analysis
Failure analysis within forensic engineering systematically examines, tests, and analyzes the failure, starting with gathering information about the component, its application, its history, followed by a highly detailed visual examination, then nondestructive testing. Some examples of nondestructive testing include magnetic particle testing, dye penetrant testing, and low magnification stereoscopes that lead toward higher magnification examinations and destructive testing.
A standard forensic metallurgical failure analysis might include the following steps:
- Collect the background information on the component and service history.
- Perform a visual examination of failed and related components in the as-failed condition. Perform low magnification examinations using a stereomicroscope to locate critical areas for further analyses or testing. Take dimensional measurements as needed.
- Analyze fractures or degraded surfaces using SEM (Scanning Electron Microscope) at high magnification.
- Using the SEM, determine the failure mode and origin site. Investigate the site for unusual conditions or contributing factors, then identify and characterize the failure mechanism such as fatigue, embrittlement, overload, corrosion types, and so on. Investigate unusual stress risers.
- Select, prepare, examine, then analyze a cross-section microstructure in the failure region while analyzing the manufacturing reflected in the microstructure and probe for possible flawed conditions. Inspect material quality heat treat conditions.
- Perform chemical composition analyses for alloy and any impurities, coatings, or platings.
- Perform mechanically and other testing such as hardness, strength, and toughness.
- Analyze, organize and present all gathered evidence and test results to formulate an engineering option and conclusion to work toward a solution.
What is SEM?
SEM, or Scanning Electron Microscopy, is an invaluable tool in conducting failure analyses of metallic and non-metallic components and is used in some capacity for a large percentage of investigations performed by industrial companies around the globe. An SEM microscope is a powerful and vital tool in determining the origin mode direction of propagation of fractures or cracks and is used in conjunction with detailed documentation via macrophotography and stereomicroscope to give a complete, exhaustive representative of the features or components being examined.
How does SEM Work?
SEM works by bombarding surfaces of samples with a focused beam of electrons. The electron beam then excites the material's electrons, resulting in the release of secondary electrons. As another option, the electron beam can be backscattered by the sample and reemerge from the sample surface. Both secondary and backscattered electrons can then be collected and displayed to provide an image of the surface being evaluated. The former provides a much greater resolution of the surface features. The latter reveals more significant topographic surface details with information regarding the atomic weight of the surface being investigated. Each type of electron plays a precise role in analyses via SEM, depending on the objections.
Other Methods of Failure Analysis involving Microscopes:
- Optical microscope
- AFM (Atomic Force Microscope)
- Photoemission microiscope (PEM)
- X-Ray microscope
- Infra-red microscope
- Scanning SQUID microscope
- LSIM (Laster Signal Injection Microscope)
As the electronic industry shows clear trends toward miniaturization with increasing functionality, modern printed circuit assemblies are becoming more complex. Today, electronic devices are virtual labyrinths of interconnected devices comprised of many hundreds of components and thousands of individual signals routed through a network of metal, plastic, and dielectric material. The reliability of the connections between individual components and the PCB (printed circuit board) must be extremely high, which is why failure analysis using many analytical investigation methods, such as x-ray, micro-ohm measurements, and microscopy analysis, is a critical tool.
Optical microscopy investigation is one of the most common and powerful tools for evaluating electronic assemblies and is the most often applied during failure analysis. Microscopes can be used to detect nonconformities on electric assemblies and document samples as received.
Since electronics devices have become smaller and slammer, they are also becoming increasingly vulnerable to all kinds of contaminations. Most of these contaminations occur at the microscopical scale and can lead to complete malfunction. Knowledge about the chemical composition of the electronics in most cases can reveal the origin of the contamination and allow effective troubleshooting. FTIR-microscopy, such as the Meiji EMT Stereo Microscope on BD-LED stand with dual arm fiber-optic illuminator for just one example, can analyze tiny structures. FTIR-microscopy can carry this analysis down to the micrometer range and is capable of identifying organic and inorganic components.
The chief advantage of microscopic failure analysis is how vastly greater the depth of field can be. Examination at magnifications ranging from 5x, to, in some cases, over 50,000X permits documentation of large samples and regions of a sample.
Microscopy is one of the most widely used, nondestructive failure analysis tools. It is both rapid and convenient in locating and identifying external defects. When used with micro-sectioning, it can become an even more powerful tool for manufacturing industries.