Bad Soden, Germany,

Dual use of cooling

CoolSold optimises PCB production

The trend towards miniaturisation in electronics continues unabated. The fine solder joints that are necessary for this have to be perfect, otherwise function could be impaired. That is why nitrogen is used as a shielding gas during soldering. The new CoolSold process from Messer uses the low temperatures of the gas to optimise costs and environmental impact.

PCB assemblies like the ones used in our laptops, mobile phones and MP3 players are mostly manufactured using the reflow soldering process. This process allows precise production of the electrically conducting connections without which such devices would not be possible. Under a shielding gas atmosphere, there is greater wetting action and the formation of metal oxides is prevented, thereby minimising the defect rate.

Nitrogen is best stored in the cryogenic liquid state. Before being piped to the soldering machine, it is first evaporated. This is actually wasteful because the production of liquid nitrogen uses a great deal of energy. The air vaporisers used for evaporation ice up, regardless of whether it is summer or winter. Particularly in winter, however, the nitrogen does not get warm enough because it can reach air temperature at most. Unwanted condensation forms on the pipes in the production halls.

At the “other end” of the process – the output end – the PCB assemblies need to be cooled down after soldering. The gaseous residues are also condensed at this stage. This requires cold, which in conventional systems is usually provided by electrical cooling units.

The CoolSold process uses the cold that is generated during evaporation for the soldering machine’s cooling circuits. A special heat exchanger prevents the coolant from freezing upon contact with the liquid nitrogen. As well as preventing condensation, the dual use of the cryogenic nitrogen means that the heat needed for evaporation is also supplied reliably in any weather conditions. The “cooling energy” that is given off is supplied evenly over the whole year to the PCB production cooling circuits. This means that you can make considerable energy savings, cut costs and reduce CO2 emissions.