Investigating Thermocouple Attachment Methods on Printed Circuit Boards During Vapour Phase Soldering

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Dr. Géczy Attila
Department of Electronics Technology

Vapour Phase Soldering is an alternative reflow soldering method, which had a comeback after the introduction of the Galden fluid. The heat transfer in a VPS oven is totally different from the conventional soldering methods, such as convectional and IR radiation soldering. Most of the energy is transferred to the board during the condensation of the Galden vapour. The appropriate heat profile became much more important since lead free soldering became the standard method. Printed Circuit Board temperature profiling is usually done with thermocouples attached to the board itself with different attachment methods. I used an unprocessed laminated PCB during the measurements. Standard K-Type thermocouples were attached to it with the standard methods, such as thermocouple fixing with Polyimide tape (Kapton tape), SMD adhesive, High-Temperature Solder (HTS) and Aluminium tape (AluTape); then I compared them from different approaches. The main target was to find the reliability issues of the soldering temperature profiling according to the different methods, highlighting the repeatability during continuous, profiling. I also considered the special effects of the film condensation during the investigation. It was shown that the HTS and AluTape methods yield the best results. The recommended method depends on the application area, the mounting surface’s material and complexity, as well as the specific measurement conditions. The Kapton tape attachment is not recommended for precision applications.


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