Investigating Vapour Phase Soldering on Flexible Circuit Substrates

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Dr. Géczy Attila
Department of Electronics Technology

Vapour phase soldering (VPS) is a developing method for electronic assemblies. Nowadays, the analysis of the technology occupies the minds of many professionals and the evaluation of the different areas of application is also a significant topic of discussion. The use of the vapour phase soldering technology on flexible printed circuit boards is not detailed in the literature, which makes it worth doing extra analysis and experiments involving the combination of the two areas.

During my thesis I got familiar with the reflow soldering processes, concentrating on the vapour phase soldering technology. I acquired a deep understanding of the process itself. Then I analysed the devices offered by the most renowned companies and gathered information about their special features. Next I got familiar with the features, the structure and the application areas, in relation to the technology of the flexible printed circuit boards.

The overall objective of my experiment was the analysis of the use of the vapour phase soldering technology on flexible printed circuit boards. It was a fundamental objective of mine to determine what effect the different thermal capacities and other material parameters of the different substrates have on the soldering thermal profiles and on the emerging solder joints. For this reason I analysed the temperature of pre-prepared disks in the cases of different arrangements and supporters, therefore measuring the thermal profiles of the two different substrates under the same conditions.

Afterwards I studied the thermal profiles of the substrates I intended to solder, then using the results I soldered components onto test assemblies with the help of the department’s paste printer, manual pick-and-place machine and vapour phase soldering oven.

This was followed by the evaluation of the emerged solder joints. I analysed them with an x-ray appliance, to examine the voiding of the solder joints. This was followed by a shear test, which I used to analyse the strenght of them and to establish what effect the differing material parameters of the substrates could have on the force of the solder joints.

As a result of my thorough analysis I have come to the conclusion that in terms of the force and the voidance of the solder joints there is no sign of significant difference, however, the causes of the variation in thermal profiles must be disclosed. Later on, further alterations caused by material parameters will have to be examined as well as the factors that influence the wetting of surfaces and the differences resulting from the rugosity of surfaces, as they could all be influential factors.


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