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24 The PCB Design Magazine • October 2015 opening in this area will cause excessive stress levels in the enclosure. Or marketing might specify a compact en- closure, a wide range of electrical features and a long battery life. Electrical designers may be well along in the design process before they are informed by the mechanical engineering team that there is no room for a battery with suffi- cient capacity to meet the spec. Another limitation of current design meth- ods is that traditional 2D PCB design systems are used to design one PCB at a time in iso- lation from the other PCBs within a product, and also in isolation from the enclosure. Veri- fying board-to-board connectivity in today's 2D PCB tools is a manual process, and one that is prone to error. When mechanical en- gineers don't have precise information on the electrical design or electrical engineers have inaccurate information on the mechanical de- sign the result frequently is that connectors don't mate with package openings, compo- nents interfere with the enclosure, etc. Using current design methods, problems that cross the electrical-mechanical divide often are not identified until the prototype stage, at which point they are expensive and time-consuming to resolve. Another disconnected aspect of the tradi- tional design process is that the chip, package and PCB are typically designed with three in- dependent design processes, carried out with point tools where data interchange requires time-consuming manual processes. In the past, this approach was acceptable due to lack of alternatives, and because most electronic products had large form factors making pack- age optimization less critical. With increasing functionality, tighter cost constraints, and the decreasing form factor of today's products, the need for vertical integration of chip, package and board is becoming more mainstream. This is particularly true for the growing proportion of products utilizing complex new packaging solutions such as package-on-package (PoP) and system in package (SiP). These new technolo- gies, combined with the increasing functional- ity of single package modules, create vast new challenges for package designers and the IC and PCB designers who must integrate the package into their own work. Moving to a Product-Centric Design Process The basic idea behind a product-centric design methodology is to optimize and vali- date product architecture prior to moving into a collaborative 3D detailed design pro- cess with product visualization. Product-cen- tric design begins with a product-based vir- tual prototyping step bridging requirements definition and detailed design using a design tool that integrates product level bill of mate- rials (BOM), functional design, PCB planning and space planning. During this phase, archi- tectural decisions can be made that involve cost, number/size of PCBs, PCB orientation, weight, enclosure size, battery size, and more. Important decisions can be evaluated collab- oratively with the ability to make trade-offs before committing to detailed design. Any design change in one planning discipline is immediately propagated to the others with a change notice. The design change can be ac- cepted, or if questionable, can drive a design discussion for resolution. The functional design can be created using an existing detailed design, BOM-based func- tional blocks or reuse blocks in order to speed up the design process. Users can also incorpo- rate reference designs provided by SoC manu- facturers. The product-level BOM supporting multiple boards is immediately available and can be evaluated by procurement or manufac- turing. The functional design is immediately available for PCB planning. feature Figure 2: Product-based virtual prototyping. ACCELERATING THE DESIGN CYCLE