Better quality of soldered joints through rapid laser-beam reflowing

摘要

Rapid laser-beam reflowing turned out as an effective method for improving the structure based characteristics of solders and joints - all the more with the application of higher melting contemporary Pb-free solders. The basic investigations on laser-beam induced rapid reflowing processes and the generation of grain-refined, restructured solder joints and metallization systems have been carried out on several unleaded alloys. The experimental tests have been concerning to stucture, hardness, shear strength, wettability and long-term behaviour. Grain refining and higher strengths of solder joints have been detected as the most substantial results after rapid reflowing. Leads which were laser-beam soldered under rapidly reflown solder showed about 10...40% higher shear strengths than in case of using non reflown solder. The maximum shear strengths have been attained by using rapidly reflown SnAg3, 8Cu0, 7Sb0, 2. Higher strength appeared in consequence of grain refining and increasing hardness, but also of a structure stabilization due to Cu diffusion. Structure characteristics and strength did not weaken even after extended TCT.