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Vapor phase soldering (VPS)
Vapor phase soldering (VPS) is used during the assembly of PCBs with heat- sensitive components. Here, the steam from inert liquid fluoride is used as heat carrier, mostly Fluorinert FC-70 by 3M which has a boiling point of 215 °C. This method has the following advantages: 1) in the vapor phase, temperature is homogeneous that does not allow the selection of almost any modules, but prevents heat damage to the circuit board; 2) less overheating during infrared reflow soldering allows for easier removal of flux residues; 3) a weakly activated flux can be used because the solder does not oxidize in the vapor phase; 4) comprehensive warming makes it possible to mount smaller chips in larger components. The current high price of inert liquid and the risk of contamination by flux prevent widespread utilization of the procedure. However, ways of improvement are being researched, for example preventive measures against the escape of steam and the use of additional heat sources.