Multilayer boards have three or more circuit layers; some boards have as many as 60 layers. The most widely practiced method of making multilayer boards is by bonding or laminating, layers of patterned, pre-etched, undrilled copper-clad laminate together. Interconnections between different layers are made through PTHs.  After lamination, the subsequent manufacturing processes for MLBs are more or less the same as those used for DSBs made with the PTH process. Because of the advent of the mass lamination technology, four layer boards, and in some cases, six layer boards can be made with almost the same case as DSBs. Therefore, four layer boards are by far the most popular MLBs. In most MLBs used for mainframe computers.

 Since the cost and reliability of the MLBS process have improved, the use of MLBs is no longer limited to computers, telecommunication and military equipment. It has spread everywhere, even into the toy industry.