What Is Materials Characterization?

Understanding the materials used in any physical device is fundamental to any product development effort. This process, called materials characterization, is a systematic measurement of a material’s physical properties, chemical makeup, and microstructure. 

Materials engineers and scientists use a wide range of analytical techniques and testing procedures to gain useful information to drive design choices, facilitate accurate simulation, and support forensic investigations. Characterization techniques can be divided into two categories. The first is microscopy, where various devices are used to look into atomic, molecular, and crystal structures. The second is macroscopic testing, where the bulk characteristics of the material are measured. 

How a material behaves is fundamentally determined by the elements in the material and how they are arranged on the microscopic and macroscopic scales. And that behavior is critical because it determines the performance and robustness of the product. Although standards exist to represent the ideal configuration of a material, variations in processing and the effects of manufacturing can cause deviations that change how a material performs. Materials characterization is used to capture those deviations and determine details beyond the standards.

A few of the more impactful benefits of this important field in materials science are:

Driving New Material Innovations

A deep understanding of bonds in polymers, crystal structure in metals, or magnetic permeability in a new alloy can lead researchers to new formulations and processes for material synthesis. 

Guiding Material Selection

Rather than engage in trial and error with expensive prototypes, understanding a material’s characteristics helps engineers select the right material for their most challenging applications.

Providing Properties for Simulation

Virtual prototypes are only as accurate as the inputs provided in the model. Accurate and detailed material properties enable pervasive simulation to drive product development and grow understanding of product performance. 

Giving Insight Into Failures or Poor Performance

When a product underperforms or fails, the next step is to understand why. Forensic analysis that includes materials characterization can lead to a deeper understanding of the root causes and inform the path to needed changes. When failures lead to legal cases, proper materials characterization can determine the outcome of litigation. 

Defining Application Boundaries

Products are designed to meet specific specifications. However, variations in material structure and material properties can increase or decrease the longevity or operating range of a product. Knowing those variations, combined with simulation and testing, can determine acceptable operating ranges.

The applications of materials characterization are as broad as the characteristics that can be measured. A well-equipped materials characterization facility can measure everything from the arrangement of atoms in a thin film layer on a semiconductor wafer to the surface hardness of a ceramic.

However, the most common measurements revolve around material composition, microscopic structure, and physical properties — and the three can be combined for maximum insight, such as materials characterization for electronics reliability applications.

Material Composition

The chemical composition of a material is a significant driver of its performance. A few atoms of aluminum in a titanium alloy can drastically change stiffness and yield strength. Measuring the atomic composition of an alloy under development or in production with the appropriate type of spectrometer is a common practice.

Spectroscopy and diffraction techniques can also be used to capture how the composition is structured. Measurements such as where various atoms sit in a crystal or how long polymers are crosslinked are needed to capture the bulk behavior of the material. Various types of microscopes can also be used, with contrast agents, to reveal composition.

Microscopic Structure

A material's properties are also driven by its microscopic structure. In metals, the crystal topology drives many mechanical and electrical properties. The arrangement of various crystals and the geometry of the boundary between crystals, grain structure, is another important material characteristic on the microscopic level. Grain size and structure are significant drivers of fatigue life and yield strength.

Optical and electron microscopes are the most common tools used to measure microscopic structures. Diffraction techniques can also be useful for looking inside materials. The results are usually presented as an image that aids material scientists in understanding the internal makeup of materials.

Physical Properties

Most engineers, outside of material scientists, deal with physical properties that summarize bulk mechanical, thermal, electric, and electromagnetic behavior that is independent of geometry. Values like Young’s modulus, Poisson’s ratio, density, electromagnetic permeability, thermal conductivity, fracture toughness, surface roughness, and electrical resistivity are familiar values that are used in hand calculations and simulations.

Physical property testing is done with various common devices, such as stress-strain machines, thermocouples, electrical meters, and electromagnetic field (EMF) probes. Most properties have standard tests defined by regulatory bodies so that any laboratory conducting a test will produce the same results.

Materials Characterization for Electronics Reliability Applications

A powerful example of materials characterization is the application of the field to electronics reliability. It is an area where measurement of material composition, microscopic structure, and physical properties are combined to assist engineers in developing electronics packages, from an Internet of Things sensor on a flex circuit to a multiprocessor motherboard. 

Electronic assemblies are made from tens to hundreds of different parts, all having multiple materials. During manufacturing and in the field, those components see temperature changes, shock, vibration, bending, electromagnetic fields, moisture, and sometimes UV radiation. And all of these values must be measured over time. 

The goal of this subset of materials characterization applied to reliability engineering services is to understand and improve the reliability of the system by providing electrical, mechanical, and reliability characterization of the electronic components and the flexible or rigid printed circuit boards that the components are attached to. 

Most suppliers don’t provide this information, so this type of testing is usually a scheduled part of the product development process. 

Whether you’re doing materials analysis at a state university or in a corporate materials characterization lab, the goal is the same: to use test equipment to measure a physical property, the composition, or the internal geometry of a material.

The following table lists the most common characterization processes and what they’re capturing.

Although materials characterization is a well-established branch of materials science that is leveraged in academia and the industry on a daily basis, some significant challenges to its effective use remain. Many of these challenges deal with the advanced physics and sensitive equipment used to measure on the atomic or microscopic scale. The macroscopic measurement of material properties can also be difficult or expensive when not deployed correctly.

The following is a list of seven of the most common challenges.

1. Capital Costs

The complexity of equipment and sensors makes many of the devices needed for materials characterization expensive. Also, the infrastructure needed, such as clean rooms, pure gasses, vacuum pumps, and more, contributes to considerable upfront costs before a single test is run. Using an outside partner or university resources can save on capital outlays.

2. Matching Needed Information to Characterization Techniques

Whether developing a new material or doing forensic analysis on a failed part, a common challenge is identifying characterization methods that will provide useful information. Consult with an expert to work with the material, product, or quality assurance teams to outline the proper analysis.

3. Material Variability

Most material production processes create a level of variability in the characteristics that you want to measure. This requires what can be a large sample size for each analysis, increasing cost and lead time. An upfront understanding of variability coupled with good statistical techniques can help minimize sample sizes.

4. Interpretation of Results

The output from most materials characterization is not a simple number. It is often a set of data that requires statistical analysis and reduction. Alternatively, with many types of microscopy, a large number of images are produced that require expert interpretation. Both require experts to take the time to evaluate and interpret the results — experts who can also translate those results into useful information.

5. Narrow Capabilities of Each Technique

One reason why there are so many different technologies for materials characterization is the reality that most technologies have a very narrow application. They may only work on nanomaterials or on thin samples, or they might only measure electromagnetic fields in a certain frequency range. This means the use of multiple techniques is required to fully characterize a material. The best way to minimize the impact of this challenge is to prioritize the analysis needed and limit evaluations to only what is absolutely required.

6. Lengthy Lead Time

Many of the techniques use required time-consuming sample preparation, lengthy testing processes, and expert interpretation. This, coupled with a possible backlog on a particular device, results in long lead times in the range of weeks and possibly months. Proper scheduling and resource management can reduce schedule impact.

7. Categorizing, Storing, Retrieving, and Transferring Material Characteristics

Materials characterization technologies create a significant amount of data that must be categorized properly, stored in an accessible location, retrieved quickly when needed, and transferred to other users as required. A proper set of procedures and a comprehensive material data management system should be put in place to manage your material intelligence.

Understanding the materials you are researching, choosing, or using in production is easy to take for granted. This is especially true for material information on components that are acquired from suppliers. Taking the time to identify, gather, and use this critical information is something that should be part of the product development and lifecycle management processes.

Providing the proper solutions and services for materials characterization can give a company or research institution a significant competitive advantage. Although it’s important, it may not be practical to build and maintain a comprehensive capability in-house. That’s why it’s essential to find the right partner for your materials characterization solutions and services.

Ansys provides world-class materials characterization as part of its reliability engineering services. This experienced team can provide electrical, mechanical, and reliability characterization. Because Ansys is the world leader in simulation, our team knows how to obtain the right information to drive your simulation-driven product development or failure analysis processes.

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