Laser Acoustic Test System LAwave

The LAwave measurement system developed at Fraunhofer IWS is used for fast and non-destructive characterization of coatings and surfaces. The underlying method is scientifically established and is increasingly gaining importance in the industrial sector for research, development and quality control.

It is based on the principle of laser induced surface acoustic wave spectroscopy. The frequency-dependent propagation velocity is determined, which depends directly on the layer thickness, density and effective elastic properties. Material defects such as pores, cracks and delamination are therefore measured indirectly.

Depending on the application, the raw data can be evaluated with a physical material model, correlated with independently measured properties or evaluated with good/bad training.

Features

• Non-destructive
• Measuring time of less than one minute
• High reproducibility
• Complies with EN 15042-1
• Extremely wide range of applications
• Fully integrated software with different user levels
• Measurement and evaluation can be automated
• Integral information over measuring area (approx. 5x10 mm²)

Materials and Materials

Modulus of elasticity, thickness and density of:

• PVD coatings, e.g. ta-C and a-C:H
• CVD coatings and CVD diamond
• Thermal spray coatings
• Laser cladding
• Single crystal semiconductors, Si wafers
• 3D generated materials (e.g. LSM)
• Solid materials, e.g. steel, brass, aluminum hard metals

Depth of:

• Near-surface damage in silicon wafer processing
• Work hardening after surface processing
• Hardening depth and nitriding depth

The method measures all influences in coatings and surfaces that affect the propagation of surface waves. We are happy to advise and test your application.

Development and Setup of Measurement Systems

For more than 30 years, the Fraunhofer IWS has been developing methods, software, measurement systems and test concepts for surface acoustic wave spectroscopy of customer specific tasks. More than 35 of our stationary instruments are used worldwide in universities, development and testing laboratories for R&D and quality control.

Our latest development, the portable measurement system LAwave mobile, now allows to bring the test probe to the surface. This makes it possible not only to inspect large shafts and inner tubes, but also to enable, for the first time, non-destructive quality control on coated, complex components. 

We have distributing partners in Japan, USA and China, providing sales, service and consulting for many international partners directly. 

Software

The specially developed software controls the measurement and allows reproducible data acquisition, its processing as well as evaluation by means of a material model. The intuitive user interface can be used in three different modes: 

• Basic: Automatic execution of predefined measurement and evaluation procedures
• Advanced: Automatic or manual measurement with extended setting options
• Scientific: Complete manual control over individual steps and intermediate results

Science and Research

We participate in publicly funded projects and test new ideas, methods, sensors and concepts with partners from research and industry. Numerous activities result in joint publications.
 

Current Development Focus

• Development of a mobile measuring head for large components, difficult to access surfaces and field use
• Automated mapping of components
• Quality assurance for thin coatings (CVD, PVD), laser buildup welding and thermal spraying
• Support of development for REACH replacement coatings and repair processes such as cold spraying
• Sensor development for measurement up to at least 600°C
   

Example Applications

• Quality control of tetrahedral amorphous carbon coatings (ta-C): Allows measurement of coating thickness and Young's modulus. The latter correlates with hardness.
• Coating development of novel brake disc coatings to evaluate porosity and mechanical integrity.
• Failure analysis of thermal spray coatings: Effective Young's modulus correlates with unwanted microcracks, pores, and bonding defects even in complex coating stacks.
• Process optimization in wafer processing: The depth of damage remaining in semiconductor materials after sawing, grinding and polishing can be precisely determined.
• Case hardened steels: The depth of hardened zones (up to 1 mm) can be evaluated, since the microstructural transformation during hardening also changes the elastic modulus.