Methods of bonding two aluminum-comprising masses to one another

A method of bonding a first aluminum-comprising mass to a second aluminum-comprising mass, comprising:

• providing a first aluminum-comprising mass and a second aluminum-comprising mass, the first aluminum-comprising mass having a first surface and the second aluminum-comprising mass having a second surface;
• exposing at least one of the first and second surfaces to a mixture comprising HF and HNO3;
• after the exposing, physically contacting the first surface with the second surface;
• pressing the first and second mass together to bond the first mass to the second mass;
• and
• wherein the first and second aluminum-comprising masses correspond to a backing plate and a physical vapor deposition target, respectively, and wherein the pressing comprises:
• joining the target and backing plate in physical contact with one another;
• compressing the target and backing plate together under a load that progresses sequentially as follows:
• (1) the load is maintained of a first pressure of at least about 4 ksi for a time of at least about 20 seconds;
• (2) the load is increased by at least about 0.5 ksi to a second pressure;
• and
• (3) the load is maintained at the second pressure for at least about 20 seconds.