The Role of Thermography in Electrical Engineering and Electronics

Contactless measurement of surface temperatures with an infrared camera is enabled by the use of infrared thermography in electronics and the electrical industry, without the need for contacting temperature sensors. As a non-invasive and refined optical temperature measurement method, it can simultaneously and temporally detect several measurement points in high-resolution.

Thermography image of microchips

Thermography image of microchips

The additional characteristics of thermography in electrical engineering and electronics are as follows:

  • Impacts neither the RF impedance of the measurement object nor the heat dissipation of the same, which safely avoids corresponding measurement errors
  • Supports the safe measurement of temperatures even on live working parts
  • Entirely records the distribution of temperature and its temporal course of complex assemblies
  • By utilizing measurement systems with detectors containing a very high number of pixels and opto-mechanical MicroScan unit, it achieves the highest spatial resolution
  • Through the use of infrared microscope lenses and close up lenses, the smallest geometrical structures can be resolved
  • Minute variations in temperature are detected utilizing lock-in measurement methods and cooled photon detectors
  • Analysis and documentation of measurement results are made simple to use with powerful analysis software

Infrared Camera Enables Contactless Measurement in Electronics

From the development of initial prototypes to mass production, thermographic inspection of electronic assemblies and components is the prevailing test procedure for quality management and failure detection. For example, this allows the detection of the following issues:

  • Hotspots and atypical temperature distributions on the surface of printed circuit boards, multichip modules and integrated circuits
  • An increase of contact resistances
  • Surplus resistance due to wire constriction
  • Concealed cracks in joints
  • Lost power because of RF mismatch
  • Invalid thermal connections of heat sinks
  • Short circuits and soldering defects, for example cold solder joints

Important conclusions can be drawn for the design of complicated electronic assemblies and the optimization of heat management by utilizing thermographic analysis in each step of development. Thermographic temperature measurement can be utilized as an adaptable instrument for quality assurance in electronics production.

High-performance thermography has become vital for setting important technological parameters and consistently monitoring these, along with inline product testing in the production process and the final functional test.

Advantages When Using Powerful Thermographic Systems

  • Detector resolutions up to (1,920 × 1,536) native IR pixels for the testing of complex assemblies
  • Capturing detailed, high-resolution images with pixel sizes up to <1 μm when utilizing particular microscopic lenses
  • Temperature differences between defective and intact structures can be detected in the range of a few micro-Kelvin because of high thermal resolution of up to <0.015 K along with the lock-in method
  • Accurate measurements of up to ±1 °C or 1% to produce correct results.

Precise Localization and Detailed Mapping of Hotspots and Temperature Differences

The theory of non-contact thermographic temperature measurement enables the accurate determination of the temperature of small objects with a small capacity for heat. Frequently this is not possible, even when utilizing the smallest contacting temperature sensors, because their heat dissipation often falsifies the measurement results.

Often, it is not possible to use thermocouples because of the function or design of the circuit itself. Additionally, temperature sensors cannot be attached to the structures of electronic measurement objects in cases where they are very small.

Thermographic systems are beneficial as they can make very small structures easily visible due to having a high spatial resolution. Along with this, they can determine the exact temperature distribution of the structure and the chronological sequence.

Utilizing specific close-ups and advanced infrared microscopic lenses, users can thermographically record hotspots of only a few micrometers in size on the component surface, for example, semiconductor components.

If SIL lenses (Solid Immersion Lenses) are also employed, even smaller structure sizes can be measured. When used with correct active thermography methods (such as lock-in thermography), temperature variations of under 1 mK are clearly visible for failure localization.

InfraTec provides matching cameras and lenses with uncooled and cooled detectors with native resolutions of up to (1,920 × 1,536) IR pixels. The spatial resolution can be improved further with MicroScan, which is available for cameras with both cooled and uncooled detectors.

The thermograms captured using this method make sure that assemblies and components are illustrated down to the smallest level of detail and that failures can be accurately localized and detected.

Thermal images with a huge spatial resolution of several megapixels are a great investment, particularly for complicated assemblies where several structures can be captured at the same time on the respective test object and measurement.

The number of images needed for the total acquisition of the measurement object increases if the pixel number of the detector of the used camera is too small.

Clear Determination of Only a Few Milli-Kelvin Temperature Differences

Generally, thermography has now secured a strong standing in applications within electrical engineering and electronics. The reasons for this entail the movement towards ever smaller, but simultaneously more powerful components which require ever lower supply voltages.

Usually, lower electrical power consumption goes hand in hand with lower temperature variations, from which any faults possibly occurring can be detected. Infrared cameras having excellent thermal resolutions of up to <20 mK in real-time operation already essentially adhere to these standards.

Although, this alone is not enough for particular measurement tasks. Additionally, lock-in thermography will be needed to analyze the slightest differences in temperature. By utilizing periodic excitation, test objects can be analyzed for irregularities and defects in a non-harmful manner.

When employing the lock-in method, the measurement time significantly increases with the intended resolution in comparison with real-time measurement and can take several minutes. As such, it is especially beneficial if these kinds of measurements can be made at the same time with a large-format camera containing high geometrical resolution.

In contrast, a camera with a lower geometrical resolution means that measurements must be repeated several times throughout the total acquisition of the measurement object, particularly if a failure cannot be reliably reproduced all the time.

The initial cost saved on buying a cheaper camera causes the developer to waste a lot of time on production or testing in the final inspection, resulting in significantly higher costs.

Excellent Coordination of Infrared Camera, Thermography Software and Peripherals

InfraTec gives special attention to the optimal interaction between the software and the thermographic camera. In the context of electronics manufacturing, the IRBIS® 3 thermography software provides a large range of functions that enable the utilization of active and passive thermography methods.

For example, these include the comparison between present thermal images and a reference image along with the display of phase images and amplitudes with adjustable parameters for lock-in thermography. This helps the failure target to be accurately identified and visibly displayed.

The IRBIS® 3 also provides a customized solution for thermographic measurements on hybrid assemblies and printed circuit boards. A significant challenge with these types of measurement objects is due to the high amount of components used. These again are made from various materials, such as different plastics, ceramics and metals, all with highly different surface characteristics.

The emissivity of the respective material at the surface is of particular importance for accurate temperature measurement.

The emissivity for each particular pixel can both be adjusted and determined using the IRBIS® 3 software. Therefore, the measured temperature can be instantly corrected, taking into account any reflected temperature and emissivity. Different correction models can be utilized for this and other influencing factors as well.

Reproducing the respective measurement situation, these models take into account all factors influencing the measurement result, such as damping properties of the measurement section, windows used or radiation from the surroundings, are taken into consideration. This allows accurate temperature measurement results to be achieved if the required conditions are met.

Individual Configuration of Thermographic Systems for Electronics and Electrical Engineering

According to the respective task, users can configure the equipment to meet their specific requirements. The first stage will commonly be the selection of a thermographic camera.

The following questions should be explored to meet the user’s specific needs: an uncooled or cooled detector? Which detector format? Does the thermographic system enable lock-in thermography? How much flexibility is required for the distance between the camera and the object of measurement? What influence does this hold on the selection of microscopic lenses and close-ups?

According to the answers of these questions, InfraTec can provide thermographic systems of varying performance levels, from the individual camera to the automated modular E-LIT test bench.

VarioCAM® HDx Lock-in

VarioCAM® HDx Lock-in

VarioCAM® HDx head Lock-in

Electronic / Semiconductor Testing - E-LIT

Further Examples for Thermography in Electronics Applications

Thermography of a microchip

Thermography of a microchip

Thermography of a processor

Thermography of a processor

Infrared image of a microcontroller board

Infrared image of a microcontroller board

Infrared image of an electronic board

Infrared image of an electronic board

Thermal optimization of a conductor board

Thermal optimization of a conductor board

 

InfraTec GmbH

This information has been sourced, reviewed and adapted from materials provided by InfraTec GmbH.

For more information on this source, please visit InfraTec GmbH.

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