The recent installation of a new scanning electron microscope (SEM) and microanalysis system in ERA’s Reliability and Failure Analysis Group included the addition of a new automated system to facilitate rapid detection and analysis of particles.

Automated particle analysis systems were originally developed to assist with the detection of gunshot residue (GSR) particles in criminal cases. In this application the hands of the person suspected of discharging a firearm were swabbed to collect the unique particles found in the residue emitted when a gun is fired. The investigators then required a rapid method to scan the relatively large surface areas of the swabs and locate unique GSR particles that are typically only a few microns in size. The key feature of these systems was their ability to quickly scan a sample area, automatically detect and accurately analyse thousands of particles to distinguish the occasional GSR particle from a background of environmental particles (dust, mineral fibres, skin etc.).

The attributes of these systems can now be applied to a wide range of applications including:

	Determining component cleanliness, either from direct analysis of the component or analysis of a filter surface containing particles washed from the surface of the component and then filtered to retain the debris. This can be used in process engineering to evaluate in-house or external vendor cleaning methods.
	Environmental monitoring of particles deposited on surfaces e.g. data centre storage systems or airborne pollutants.
	Hard disk analysis, used by the semiconductor industry to detect foreign particles on the ultra-clean surfaces of IC wafer and hard disk drives.
	Metal inclusions or second phase particle distribution, particularly relevant in tyre cord analysis or other critical safety applications where minute particles within the materials can act as stress raisers and cause premature or un-predicted failure of the component or system.

Finding the needle
The detection system at ERA is designed to automatically detect and measure particles as small as 0.3µm in diameter, providing information on the particle shape, size and chemistry. Typically 1000’s of particles can be detected and analysed within a few hours providing a wealth of information on the types of particles present within a sample. The composition of particles the system can detect is not restricted and can include inorganic/organic, mineral and metallic particles. Having acquired data from 1000’s of particles common compositions or “classes” can be defined post-acquisition. Individual particles that have chemistries or morphologies of specific interest can also be relocated in the microscope for further analysis or observation.

Step 1: Particle data is collected using software control of the samples stage (shown here holding four circular filters).
Step 2: The location of every particle within each sample is stored allowing automatic relocation of the sample for further post-acquisition analysis or imaging.
Step 3: The chemistry, size and shape of up to 100,000 particles per sample can be stored providing comprehensive data on the range of particles present.

Practical engineering applications
Recent examples of where ERA’s customers have used this facility include:

	Automotive: The assessment of fuels to determine their effects on engine performance/wear and engine filtration systems.
	IT systems: Analysis of dust taken from data centre facilities to identify the presence of metallic particles that may and sometimes do cause shorting or other failures in sensitive electronic equipment e.g. zinc whiskers.
	Aerospace : Determining the particle content and composition within hydraulic fluid from safety critical aerospace components.
	Power generation: Measuring the size and shape of second phase particles in reconditioned turbine blades.

Further information
To find out more call us on +44 (0)1372 367444 or email.