According to the electronic devices function in the interface table, interconnection (interconnection) can be divided into five levels. ① package of internal linkage, ② pin IC package and PCB interface. For typical convergence IC Sockets. ③ printed circuits and wires or PCB interface. Typical connection for printed circuit connection. ④ backplane and backplane interface. Typical convergence convergence for Cabinet style. ⑤ interface between the devices and equipment. Typical product is a circular link. ③ and ④ levels there is some overlap. In five levels of cohesion, Mall ③ and ⑤ is of the highest level of merchandise, and now the fastest growing are the third level of merchandise.