Here you can find a selection of reference projects. Please note that some of these are subject to a non-disclosure agreement, in which case details are not mentioned in the project descriptions.
An extensive process development project: electroceramic parts were to be coated using an innovative technology. Therefore two new processes had to be developed, an etching process for conditioning and the coating process itself. In addition to the specification of the manufacturing equipment and the definition of process parameters, measurement systems for statistical process control have been developed (degree of etching, coating thickness).
In this example from the field of reliability testing a shock test apparatus for electromechanical components has been developed. The samples are placed in a test jig with defined orientation and undergo a number of uniaxial acceleration pulses with a customer-specified pulse profile. Besides the acceleration peak value, the time profile of the pulse is of special importance. The shock tester has therefore been designed to enable the fine-tuning of the pulse shape. An acceleration sensor is used to record the pulse shape in the millisecond range during each shock event.
Triggered by a new customer requirement concerning the corrosion resistance of gold-plated spring contacts of electronic components the task was to adapt the porosity test according to ISO 14647:2000 (nitric acid vapour test) and to implement it in the control plan of the component supplier. The challange was to optimise the testing procedure towards maximum reproducibility of the results – no matter if the test is carried out at the site of the contact manufacturer, the plating company, the component supplier or in the lab of the customer. The goal was reached by an in-depth analysis of testing parameters and their interactions as well as by the specification of a detailed testing procedure well beyond the specs of the ISO standard.
The contacting of thin (< 100 µm) enamelled wires in automated production lines is often realised by a fast resistance soldering process. Due to cycle time requirements the time window for the soldering process is usually in the range of 100-200 ms. The soldering temperature has to be sufficiently high to ensure proper contacting despite the short process time. On the other hand, the heat transfer to the solder joint has to be limited in order to avoid the risk of detrimental changes in the microstructure of the wire material. Knowledge of the temperature-time profile is thus of vital interest.
A measurement procedure allowing to record the temperature-time behaviour has consequently been developed. For the measurement, a thin nickel wire is soldered in addition to the enamelled copper wire, thereby forming a thermocouple. Recording of the thermovoltage as a function of time yields the desired temperature profile, especially the cooling curve of the solder joint. The big advantage of this method is the combination of high spatial and temporal resolution with the simplicity of the method. Using alternative non-contact temperature measurement techniques, these features would, if at all, be achieved only with tremendous effort.
Details can be found at M. Justinek and M. Fasching, "Thermische Charakterisierung eines Widerstandslötprozesses", PLUS (Produktion von Leiterplatten und Systemen) 10(13), 2368 (2011). (Download PDF)
During operation, the amplifier to be investigated shows pronounced heat-up particularly of the housing in the region of the power transformer as well as the tubes of the power stage. A thermographic study has therefore been conducted to determine the maximum temperatures under long-term operating conditions. As a measurement system, a FLIR T420 thermographic camera with 18 mm optics has been used*.
Upon determination of the emissivity of the test objects (transformer windings, glass bulb of the tubes) by comparison with a reference tape, and determination of the reflected temperature at the position of the test objects, the temperature-time profile has been recorded after switching-on of the cool amplifier (starting temperature 25 °C) until a stable temperature was reached. The cooling phase after switching-off has also been recorded.
The heating and coolig curves of the transformer are shown in the figure below. The power transformer is heating up to 92 °C during a time of 7 h. The cooling phase is also quite long, it takes another 7 h until the starting temperature is reached again. Considering the removal of the lateral cover enabling thermal convection to some extent during the measurement, it can be stated that the top temperature under standard operating conditions may be even slightly higher.
The following graph shows the thermographic image of the electron tubes after temperature stabilisation (after 18 min operation). Depending on their heating power, the different tube types reach different temperatures. Operating temperatures on the glass bulb of the tubes are 84 °C for the pre-amp stage, 120-150 °C for the driver stage (there is a difference between left and right channel) and 239 °C for the power tubes.
* Special thanks go to mfTEC Faschig KG for provision of the thermocamera.
DI Dr. Martin Justinek firstname.lastname@example.org + 43 699 123 67 900