Diffusion bonding of copper at low bonding temperature and pressure was studied with the purpose of obtaining no deformation bonding. OFHC (JIS C1020P) was used for copper plate (80 mm diameter×8.7 mm thickness) and its surface was machined finely to roughness Ry 20 nm, flatness 0.3 μm/80 mm diameter by ultra precision lathe. Main bonding parameters were varied 573-973K (bonding temperature), 0.005-0.15 MPa (bonding pressure). Another parameters were applied constant value, 3.6 ks (bonding time), 4×10-4 Pa (atmosphere). Optimum bonding parameters attaining high joint strength and extreme small deformation was selected from test results. Finally, trial production of accelerating cell (X band cell) on Japan Linear Collider Development Plan was done by diffusion bonding method obtained with this study.
Main results obtained are as follows :
(1) Excellent joint properties which joint strength was equivalent to base metal and joint deformation was extremely small (limit of measurement) were obtained with following bonding parameters.
Temperature : 773-973K Pressure : 0.01-0.15 MPa (Temperature : 773 K)
0.005-0.05 MPa (Temperature : 973 K)
Time : 3.6 ks Atmosphere : 4×10-4 Pa
(2) Trial production of accelerating cell (above mentioned copper plate was lapped 30 pieces) was done with diffusion bonding (temperature : 973 K, pressure : upper joint 0.02 MPa-bottom joint 0.04 MPa, time : 3.6 ks, atmosphere : 4×10-4 Pa). Excellent leak tightness (<3.6×10-12 Pa·m3/s) and extreme small deformation (direction of diameter and axis) were obtained. These results indicated practical use.
