The Development of Cost and Size Analysis for the Assessment of Embedded Passives in Printed Circuit Boards
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Passive components are electrical components that do not provide amplification or gain. The primary functions of passive components are to manage buses, bias, decouple power and ground (bypass), filter, tune, convert, sense and protect. In 2001, passive devices accounted for 91% of all components, 41% of board area and 92% of all solder joints in an electronic system but only 2.6% were integrated in some fashion. The integrated circuit industry is achieving faster speeds by shrinking technology. This dictates that the passive solution must also shrink. In addition, the need to drive out every cent of costs, improve product reliability and the high passive to active ratios have motivated system manufacturers to consider higher levels of passive integration. These factors have increased interest in embedded passives. This research examines the size and cost tradeoffs associated with the use of embedded passive technology for resistor and capacitors, and creates the models and methodology necessary to determine the coupled size/cost impact of embedding passives. It also examines the effects of embedding resistors on profit margin and throughput. A version of the model for performing tradeoff analyses is delivered via the CALCE Consortium and used by board manufacturers and system designers at this time. The models developed have also been used to determine the optimal number of passive devices to embed in a given system by implementing them within a Multi-Population Genetic Algorithm (MPGA). Boards from several different applications are analyzed to demonstrate the applicability of the models and the optimization approach. The effect of board size on the optimum embedded passive solution was studied and an assessment of whether better system solutions can be found was performed. The analysis has shown that the system size limitation when embedded passives are used is not only dependent on the quantity, type, and electrical properties of the embeddable components, but is, in fact, more dependent on layout constraints associated with the placement of the non-embeddable parts. Studies indicate that the higher the embeddable passive density, the greater the probability that placement can be improved when passives are embedded.