Surface-Activated Bonding of Aluminum/Stainless Steel and Its Seal Characteristics

In order to consider the application of the vacuum parts to the vacuum procedures in a joining process called surface-activated bonding (SAB), we conducted a SAB experiment at room temperature for the combinations of Al5N/SUS304, Al2N/SUS304, Al5N/SUS316 flange, and Al2N/SUS316 flange. We examined the influence of the cleaning state and the surface roughness on Al/SUS joining performance, as well as the bonding strength and the sealing characteristics of such joined samples. We have found the following. (1) Before joining, smooth surfaces of the Al5N and SUS304 samples were sputter cleaned using an argon fast atom beam (FAB) for 10 and 60 min, respectively, to completely remove surface oxide and organic materials. However, these samples can be joined even if the removal is imperfect. (2) When the FAB irradiation time was longer than 20min for Al5N and 30min for Al2N, the tensile pulling tests indicated bulk fractures in Al without an interface and that the bonding strength of the interface of the joined samples was higher than the Al strength. (3) Leak rates for Al5N/SUS316 and Al2N/SUS316 samples were 1.5 × 10-11 Pa · m3/s and 2.0 × 10-11 Pa · m3/s, respectively. These are within the permissible equivalent leakage of a large ultrahigh-vacuum (UHV) chamber. The leak test behavior with time for both samples indicated stable leak rates and sustainable sealing.