Spraying of abrasive soldering paste

Elisabeth Lenz

ViscoTec has proven high expertise particularly in complex dosing environments. ViscoTec´s brand preeflow shows the capability to operate reliable, extremely precise and repeatable for various applications in many industries. With the help of the precision volume dispenser “eco-SPRAY” preeflow explores new paths.

Soldering pastes are pasty mixtures of solder powder and flux agents, which enable an accurate soldering of metals and alloys by identifying the right mixing ratio. Hence soldering pastes pose the foundation for durable and bonded connections. Due to the high share of solids soldering pastes require a special material treatment and show high abrasiveness towards the dosing equipment.

On the request of a well-known material supplier internal tests in the ViscoTec laboratory were performed. Micro-vaporization of solid containing soldering paste was the objective – with astonishing results:

Adjusting the spraying factors – air pressure (in bar), distance needle to the substrate (in mm) and robot speed (in mm/s) – a sharp-edged distribution of the fluid will be achieved. Despite the high amount of solids in the paste the spraying pattern is defined by lowest overspray, a uniform coating and a round shape.

For this specific application 0.4 g soldering paste were atomized with a spraying width of 1.1 cm. Owed to the high share of solids the specific density is 3.0 g/cm³ and the sprayed volume comes consequently to 0.13 ml. Even more impressive is the fact, that the mean deviation of the average shows an effect of 1.1%.

From a material supplier’s perspective these results mean new opportunities for the application of soldering pastes. From a customer’s perspective a more defined application with high efficiency will be realized. The consequence will be process stability and the saving of material consumption during the industrial production. The depicted comparison emphasizes the high potential which can be found in the spraying process.


Soldering paste application manual vs. eco-SPRAY

The test scenario demonstrates the ability to spray complex fluids and in spite of the materials abrasiveness no wear has been detected at critical dosing equipment. The nebulization of the soldering paste can be performed continuously or punctually. Due to the speed dependent dosing the volume is variably changeable during the whole process.

The internal ViscoTec know how enables the close coordination of all relevant spraying parameters according to customer requirements. As a result the industrial demands are met completely.