The Technique:
Laser brazing is a joining method whereby the diode laser is used to melt a metal filler material, which “wets” the parts to be joined along the seam. The wetting process is facilitated by a flux that removes surface oxides and enables a metallurgical bond between the filler alloy and the parts. Typically, the melting temperature of the filler alloy is considerably lower than the melting temperature of the materials to be joined. After resolidification, a sealed joint is formed that exceeds the strength of the filler material. Compared to laser welding, the brazing process has better gap bridging capabilities due to the use of the filler metal and less effort is need to maintain tight part tolerance and fit-ups with minimum gap. Furthermore, the lower heat input minimizes part distortion.
In addition, laser brazed joints have smooth surfaces and minimal heat affected zones. These advantages are significant when meeting demanding visual finish requirements. For example, these benefits have resulted in the use of laser brazing for critical body-in-white assembly applications. Diode laser brazing is also a quality-assured process because the key process variables are measurable, predictable, controllable and repeatable.
Diode lasers offer a clear advantage over Nd:YAG lasers in the production environment because of their lowered investment costs and efficient and reliable operation. The lasers are nearly maintenance-free and they are capable of up to 4 years in a 3 shift manufacturing operation. Lamp-pumped Nd:YAG lasers have a significantly higher acquisition costs and are at least 10 times less efficient with a footprint that is about 5 times that of a diode laser system. Nd:YAGs require expensive lamp replacement every 1000 hours along with the associated down time to perform the maintenance.
The advantages of diode lasers present a good case even for the replacement of existing Nd:YAG equipment.
