Bartels Mikrotechnik, based in Dortmund, Germany, is one of the largest series manufacturers of piezoelectric micropumps. At the same time, Bartels Mikrotechnik is developing further components that simplify the guidance of liquids in a microfluidic system and also offer simple control of the system. The mp6 micropump is the heart of the company. Thanks to a double actuator module, it pumps liquids and gases with high precision. Because of its small size (30 x15 x 4mm) and weight (2 g), it is versatile and easily added to new and existing systems.
The main material used here is PPSU (polyphenylsulfones). However, PPSU cannot be welded together arbitrarily. It needs a transparent part through which the laser beam passes and an absorbent - preferably black - part to which the transparent one can be welded. By generating heat on the black material, the PPSU melts in both parts in a controlled manner and bonds them together.
By welding the individual parts together by the laser, the pump has a life time of more than 5,000 h and a burst pressure of more than 1.8 bar.
To be able to guarantee these values, the individual welds were carefully tested. Every parameter (speed, power, defocusing and track width) has a significant role here, so the best combination of these was found out and seals the pump.
On the one hand, the pump itself is held together with four different welds, each of which has a different function and thus also fulfils different requirements. What they all have in common, however, is the stability and sealing of the pump.
On the other hand, two of the four welds are essential for the functionality and crucial for the performance. If one is not executed carefully, pressure and performance losses will occur. To avoid this, other aspect points in the production must be included because the laser parameters do not change. For example, the occurrence of poor or discontinuous welds can also indicate differences in the starting material to be welded. Due to small height differences or too high roughnesses, interfering air pockets can lead to such images. If the gap is too high, there is no contact at the points to be lasered and the laser weld remains incomplete. The same could happen if the pressure is too low and the parts do not lie properly on each other.
All in all, laser welding is one of the most important proceedings in the micropump production and is also gaining more and more importance for Bartels Mikrotechnik through the component production.