As a new welding method (except for hot plate, vibration and ultrasonic welding) LTW has recently come under the spotlight.
LTW is one of the methods of thermal welding and makes use of the heat melted resin instead of an adhesive.
However, the heat source of LTW is different from that of thermal conventional welding. The heat source of hot plate welding makes use of the heated hot plate. Vibration and ultrasonic welding makes use of the frictional heat. In the case of LTW, the heat source is obtained by absorbing heat from the laser beam on the surface of the resin.
When you were a child, you would bring the sunshine into focus with magnifying lens on the black paper and burned the paper. As for LTW, the sunshine is replaced with the laser beam, the black paper is replaced with black resin, and the light energy is converted into the thermal energy. In other words, LTW is utilized for the photo-thermal transfer of the laser beam.
You will be able to understand that the light energy of laser beam is converted into the thermal energy on the surface of the black resin and the black resin is melted. Then, how is the black resin joined?
First, when the laser light radiates the two pieces of the resin on the condition of the suitable pressure, the laser light is transmitted to the "Laser Transmission Material" and is heated (melted) on the surface of the "Laser Absorption Material". Next, the heat is melted to the "Laser Transmission Material" by means of the thermal conductivity and the melting pool is formed between the "Laser Transmission Material" and the "Laser Absorption Material". Finally, they are joined.
Laser Beam
It is necessary to radiate the laser beam of LTW. There are YAG
laser [wave length: 1064nm] and LD (Laser Diode) [wave length: 808nm, 840nm
& 940nm] in the type of resin laser beam. It is generally the most
effective to use LD with the welding of resin because of the economical
efficiency and quality of the laser beam.
