For Safe Electromobility – Thermographic Testing of Lithium-Ion Batteries

The energy efficiency of electronic components is becoming increasingly important in numerous fields of application. And that is not all: in our electronic and high-tech age, the demand is for even faster active components, higher power densities of miniaturised systems as well as absolute reliability. Along with this, there is the request for environmentally conscious resource procurement and the requirement that the increase in performance of modules should run parallel to lower energy consumption.

Today, thermographic damage and function analysis of electronic components is an established test method in electrical engineering. This method is also used for research purposes at the Institute for Electrical Systems and Energy Logistics at BTU Cottbus-Senftenberg. In this context, Prof. Dr. Ralph Schacht is intensively involved with the material and system characterisation as well as the non-destructive failure analysis of printed circuit boards, electronic components, microelectronics as well as composite systems of packaging and interconnection technology.

At Delphi’s laboratory plant “Test & Validation Services”, thermography is used for design and product validation as part of quality assurance. Therewith, a stable hardware basis is set for integrating new technologies in motor vehicles that again present a substantial contribution to traffic safety.

Contactless measurement of temperature distributions and profiles with industrial thermographic cameras permits efficient monitoring and control of temperature-dependent processes and procedures within a system-integrated quality assurance programme in industry.

Check the microstructures of sheet metal parts during the stamping process and establish a uniform high strength and quality of all produced stampings safely and with a contact-free method.

Infrared cameras allow the non-destructive and process-synchronous monitoring of coating processes to ensure that the coatings are free of defects as soon as they are applied.

Using pulse thermography, WELD-CHECK enables you a quantitative assessment of the inspected welds.

Check for long-life fatigue strength of mechanical components in load tests, using high-end infrared cameras.

Detect inhomogeneous temperature distribution and local power loss during the production using the Lock-in Thermography.

Monitor assembly halls and storage facilities fully automatically 24/7 and detect critical heat sources reliably.

Due to the binning technology, infrared cameras have two speed modes – the standard mode and the high-speed mode, in which the frame rate increases more than three times. The field of view remains constant in both modes, so the scene captured by the camera does not change. In high-speed mode, the thermal resolution also increases by a factor of two.

Behind the function is a fast-rotating MicroScan wheel, which is integrated into the camera. It ensures that four different individual exposures are taken per wheel revolution, which are offset laterally by half a pixel each. In this way, thermography achieves a new quality due to thermal images providing a quadrupled spatial resolution.

For detection of small temperature changes InfraTec's infrared cameras offer thermal resolutions up to < 15 mK in real-time operation. By using the Lock-in Thermography method it is possible to further increase this resolution significantly. For this purpose test objects are periodically excited and non-destructively examined for defects and irregularities.

Thanks to HighSense, ImageIR® users have the option of setting up individual measuring ranges based on the factory calibration that best suit the respective task. Depending on the measuring task, the required temperature range can be selected and the optimum integration time for this purpose is calculated – or one decides to proceed in reverse order. Thus, the calibration can be retained even in the case of changed integration times.

The Auto Calibration option expands the HighSense function to include automatic, dynamic adaptation of the integration time. This ensures the utmost temperature measuring accuracy and an optimised signal-to-noise ratio throughout the process. The wellfill of a detector is usually optimal in certain areas of the dynamic range. If the measured object signal is outside theses or user-specified limits, the integration time is readjusted.

The High Dynamic Range (HDR) function of the Infrared ImageIR® camera series enables measurement scenarios with extremely different temperatures to be recorded continuously. When recording in HDR mode, multiple thermograms with different integration times and different filters are recorded quickly in succession and compiled into an overall image with a high dynamic range. The measuring range can span up to 1,500 K. Users obtain high-contrast images in a wide temperature range characterized by high measurement accuracy.

The 10 Gigabit Ethernet interface of the high-end camera series ImageIR® opens this extremely fast transmission standard with a NIC specially developed by InfraTec. This works with optical or electrical transceiver modules that are easy to change and are called SFP+.

Stationary camera systems are usually used PC-controlled. Alternatively, InfraTec offers a solution that makes the operation of the camera system even more versatile. An additional tablet PC is attached to the camera housing, which enables wireless control of all camera functions. The display solution allows access to all functions of the IRBIS® online control and acquisition software, delivered together with the camera.

With the innovative EverSharp function all objects of the image scene are displayed sharply, not depending on camera distance or lens. With the help of special algorithms thermal images with different focus positions are combined automatically, so that only the sharp object structures are displayed in the resulting thermal image. Thus, thermal images turn out very impressive as all objects are displayed in superb image quality.

The multispectral feature makes it possible to record sequences with constantly changing spectral filters. Images are recorded synchronously with a rapidly rotating filter wheel equipped with the filters. It may be possible to switch between up to seven filters, depending on the version. Due to this the multispectral measurement can be optimised to suit the measuring task if the preset ranges are unsuitable. The integration times can be adapted within the limits calibrated for this filter.