| dc.description.abstract | In this study, we explored the process of heterogeneous bonding between copper and glass through nanosecond pulsed laser transmission welding. Various processing parameters, including laser energy, focal plane positions, laser line energy intensity, the total number of scans, and the impact of a thin titanium adhesion promotion layer coated with glass on bonding quality were investigated.
The effects of laser bonding energy and focal plane positions on welding quality were examined, utilizing pull-tensile separation force (PTSF) and shear-tensile separation force (STSF) measurements to assess weld strength. Increased laser welding energy enhanced weld strength up to a certain threshold, beyond which irregular hot spots led to voids or cracks, resulting in residual stress within the weld zone. The focal plane position below the glass/copper interface exhibited the highest weld strength. Additionally, weld strength measured using PTSF surpassed that of STSF, attributed to separation at the weld seam-glass boundary in PTSF and along the weld-copper interface in STSF. Pulsed laser welding demonstrated economic viability for copper-to-glass applications, achieving a maximum bond strength exceeding 10 MPa. SEM and EDS analysis revealed intra-mixing and inter-particle diffusion of Cu and SiO2 in the molten pool, while HR-TEM and SAED observations at the weld interface showed the presence of polycrystalline copper nanoparticles, copper oxides, and an amorphous Cu–O–Si region.
Exploring suitable bonding parameters for the laser bonding mechanism, considering both total scan number and laser line energy intensity, revealed a direct correlation between weld zone extent and scanning number. Control over elemental composition and microstructure was achieved by varying laser line energy intensity. The uniformity of the weld seam was attributed to the intra-mixing and inter-diffusion process, despite the different distribution of Cu micro-particles in the molten zone.
The addition of titanium thin films of varying thicknesses further improved welding performance. The influence of transmission laser welding and a thin titanium adhesion promotion layer on bonding strength enhancement was investigated. Each processing parameter′s impact on bonding quality was thoroughly examined to simplify complexities and identify an appropriate processing window. A consistent pattern of increased weld strength with higher line energy intensity was observed for a particular thickness, with a maximum bonding shear strength of 40.15 MPa achieved at 10 nm Ti thickness. SEM analysis revealed the impact of interlayer thickness on the Cu/SiO2 joint microstructure.
Chemical reactions resulting in the formation of an amorphous Cu-O-Ti compound near the Cu/SiO2 interface were identified through XRD and HR-XPS. EDS mappings provided evidence of the significant roles played by intra-mixing and inter-diffusion of Cu, Ti, and SiO2. SAED and HR-TEM observations elucidated the presence of polycrystalline Cu, α-Ti nanoparticles, CuTi, Cu2O, and an amorphous Cu-O-Ti region at the weld interface. These findings hold critical importance in enhancing the welding quality between copper and glass, rendering the joint more reliable for diverse industrial production applications. | en_US |