Solid-state joining processes involve the bonding of two interfaces without the melting of base materials. These processes can be broadly classified as (i) pressure processes, (ii) resistance processes, (iii) arc-heated processes, (iv) surface displacement processes, and (v) diffusion bonding processes (Gould 2008). Figure 1 shows the general classifications of the various solid-state bonding processes.
In this chapter, solid-state joining processes adopted to form microjoints are of particular interest. Solid-state bonding technologies particularly the thermocompression bonding and thermosonic bonding technologies used in the electronics industry will be discussed in detail in the forthcoming sections. The bonding mechanism (in relation to diffusion bonding) and the necessary bonding conditions to form reliable joints will also be presented. Furthermore, this chapter will showcase the advances in thermocompression and thermosonic bonding technologies.

Fig. 1 Classifications of the various solid-state bonding processes