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56 The PCB Magazine • October 2014 In addition to the added complexity in BOM (bill of materials) these represent, providing the current sensing function involves assembly of a number of discrete elements, adding both cost and physical bulk. Therefore designers are look- ing for alternatives within a more highly inte- grated system. Although printed wiring offers an alternative in the same way as circuit boards replaced discrete wiring in the 1950s, the prob- lem is that the mains load current must transit the assembly requiring a much larger conduc- tor cross-section than is standard with printed circuit processes. The MiB Solution The need for communications as well as de- mand-side load control represents the combina- tion of intelligence and power provided by met- al in the board (MiB) printed circuit technology. The solutions that are emerging offer the po- tential for replacement of hardware and compo- nents formerly used to manage heat and power, and range from simply providing a metal base in the board for heat dissipation to sophisti- cated solutions combining thermal and power management with high-density interconnect and formability. As a term, metal in the board is coming into general use, because these solu- tions are not metal core or metal base; they are metal in the board. The manufacturing technologies and capa- bilities of MiB range from simple three layer buildups commonly known as Al-based or in- sulated metal substrate to complex assemblies using a variety of techniques to provide low thermal and electrical resistance pathways in the board. In every case, the MiB component is providing additional functionality—thermal and/or power management. In addition to load sensing, the other primary challenge for the RTU is load switching. New generations of power semiconductors are emerging in response to the need for intelligent power management across an expanding range of applications, from auto- motive through renewable energy harvesting, appliances, solid state lighting, and RF power. THE SMART GRID OPPORTUNITY continues figure 4: schweizer combi board. (source: schweizer ag)