Figure 4 shows a schematic of a typical CPB and a thermal bump for comparison. These structures are similar, with both having copper pillars and solder connections. The primary difference between the two is the introduction of either a P- or N-type thermoelectric layer between two solder layers. The solders used with CPBs and thermal bumps can be any one of a number of commonly used solders including, but not limited to, Sn, SnPb eutectic, SnAg or AuSn.