Numerical simulation of SAC305/Cu friction inlay welding based on Coupled Eulerian–Lagrangian approach

• Published in: International journal of advanced manufacturing technology 2024-11, Vol.135 (1-2), p.119-135
• Main Authors: Zhao, Zhili, Zhang, Liandong, Wei, Jiandong, Ren, Zeyu
• Format: Article
• Language: English
• Subjects: CAE) and Design; Computer-Aided Engineering (CAD; Copper; Diffusion layers; Engineering; Flow velocity; Friction; Grains; Industrial and Production Engineering; Intermetallic compounds; Mechanical Engineering; Media Management; Melting points; Molds; Original Article; Production costs; Recrystallization; Reflow soldering; Solders; Weld defects; Welding
• ISSN: 0268-3768; 1433-3015
• DOI: 10.1007/s00170-024-14569-6

In traditional column grid array (CGA) packaging, column interconnections are achieved through precise mold positioning and reflow soldering of pre-printed solder paste. However, the presence of molds during the welding process increases the occurrence of welding defects and manufacturing costs. A friction inlay welding (FIW) method was proposed by the authors to achieve copper column connections without the assistance of molds. The study utilized the Coupled Eulerian–Lagrangian (CEL) method to model and simulate the FIW process. By integrating simulation results with experimental data, the temperature history, strain history, and solder flow behavior of the FIW micro-welding were determined. The results indicated that during the welding process, the peak values of temperature, strain, and solder flow velocity were all located at the base corners of the copper column. The peak temperature at the friction interface reached 158 °C (431 K), which was 88% of the solder melting point (490 K), with a peak flow velocity of 197 mm/s. The solder flow trajectory at the bottom of the copper column exhibits a downward spiral staircase pattern. After flowing to the edge of the bottom of the column, the solder rotates upward along one side of the column. On the side of the copper column, the thermoplastic solder near the copper column (within about 150–200 µm from the copper column) simultaneously flows in axial, radial, and circumferential directions. The flowing solder ultimately evolves into a microstructure composed of recrystallized fine grains in the stir zone (SZ) and deformed and elongated grains in the thermo-mechanically affected zone (TMAZ). The atomic diffusion between the copper column and the solder is excited and accelerated by the thermal–mechanical action caused by friction, and the connection layer composed of Cu 6 Sn 5 intermetallic compound is formed at the interface.