Development of simultaneous laser welding process applied to thermoplastic polymers

Transmission laser welding of thermoplastic polymers offers innovative solutions to overcome limitations of conventional joining technologies. Different process strategies provide to flexibility, short process time and high quality weld seams. However, even if laser beam welding of thermoplastics becomes widely used in industry, important developments are necessary with regard to the assembly process and the development of specific polymers. Generally, the assembly is done by contour welding or quasi-simultaneous welding (using scanning heads). Simultaneous welding can be another interesting alternative as well the possibility to achieve direct simultaneous welding while using an arrangement of compact and modular set up of power diode laser. This process shows important advantages as the short process time, no dynamic motion system and increased gap bridging capability. Main constraints are the control of the beam intensity distribution and the lack of flexibility concerning the seam geometry. A specific optical system to allow simultaneous welding using a conventional fibre coupled laser was developed. This beam shaping optic assures an homogeneous intensity distribution and can easily be exchanged when changing the geometry of the seam. An example of electronic packaging using this innovative process is presented in this article.