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Embedding resistors in high-speed boards and chip packages can generate significant cost savings from reduced size and reduced component placement costs.
Embedding passive components such as resistors and capacitors inside boards and chip packages can offer substantial benefits to the designer:
* Open up valuable real estate on the surface allowing increased functionality or reduced size.
* Realize any specific value of resistance or capacitance required by the design.
* Rout with shorter, lower inductance interconnects enabling faster switching speeds and reduced EMI.
* Provide greater routing flexibility by placement on inner layers and using different geometries.
* Reduce parts count for assembly, with lower placement and inventory costs.
* Eliminates solder joints, which improves reliability and achieves Pb-free compliance.
* Reduce system-level cost.
Historically, embedded passive technologies have been driven by material suppliers with some success. Rohm and Haas Electronic Materials is commercializing InSite(TM) thin-film, high-ohmic material (250-1000 ohm/[white square]) for embedded resistors, and thinfilm, high dielectric constant material (1300 nF/inch^sup 2^ or 200 nF/cm^sup 2^) for embedded discrete capacitors [1]. OEM and EMS companies have been interested in these technologies but have taken a cautious approach to designing embedded passives into new products. As the barriers to market acceptance are lowered (e.g. availability of CAD/CAM tools), designers of high-density and high-speed boards and chip packages are beginning to embrace and exploit the benefits of embedded passives technology.
Cost of Embedded Passives
Cost per unit area is a common metric in the procurement of bare boards from fabricators and is a key barrier to market acceptance of embedded passives. Embedded passive materials, process, and test add to the final bare board cost, thus unit cost of a bare board with embedded passives will be higher than a bare board without embedded passives. As shown in Figure 2, the savings from lower component, placement, and inventory costs accrue further up the value chain and so a systems-level "total cost" analysis is required to fully capture the cost benefits of embedded passives. Additional cost benefits can accrue from reduction in board size potentially lowering the cost per bare board, as will be demonstrated in the case study.
Many cost models for embedded passives have been reported in the literature with varying levels of complexity...