Microvias have been called the third revolution in printed circuitry. Are embedded passives - resistors and capacitors buried in the board - the fourth, one with even greater potential to change the face of design? While microvia circuits enable higher densities, lighter weight and better performance, the board remains at its core just a bunch of wires. With passives built in, the board is a very different entity indeed. Embedded passives are a relatively new concept. Why embed them? Lack of space on the board surface. In a typical assembly, components that cost less than 3% of the total price can take up 40% of the real estate! And it's getting worse. As we design boards with more functions, higher clock rates and lower voltages, more power and higher currents are required. Noise budgets go down with the lower voltages, and significant improvements in power distribution systems are needed. More passives are needed. This is why the use of passives is increasing at a greater rate than that of active components. Placing passives inside the board is one big advantage, but there is another. Surface solder joints produce inductance. Embeddeds eliminate the solder joints, thus lowering inductance, which reduces power system impedance. So, embedding resistors and capacitors saves precious surface area, shrinks the board and cuts weight and thickness. And by eliminating solder joints, reliability is improved (solder joints are the leading failure mode of assembled boards). Embedded passives permit shorter leads and closer component placement, thus enhancing electrical performance.
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