Laser transmission welding of transparent plastics parts in micro technology

Most welding processes for plastics do not meet the special demands of micro technology. Laser transmission welding, however, features distinctive advantages like low mechanical and thermal load of the joining parts. Hence it is particularly suitable for the welding of micro plastics parts. Certain optical properties of the components to be welded are needed though. While one of the welding parts has to exhibit a high transmittance in the range of the laser wavelength the absorptance of the other one has to be high enough to ensure a sufficient absorption of the laser radiation to plasticise the material. Here, carbon black has almost exclusively gained industrial importance, since it is an inexpensive material with good absorbing properties. However, it leads to a black coloration which is not always acceptable. Recently, there are special pigmentations which allow for a non black colour in the visible range of light, but nevertheless absorb laser radiation. Up to know, only few is known about their welding characteristics, so that it has to be investigated whether they are suitable for the application in micro technology.