AWR White Papers

EDA Software Design Flow Considerations for the RF/Microwave Module Designer

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Overview Miniaturization of consumer products, aerospace and defense systems, medical devices, and LED arrays has spawned the development of a technology known as the MCM, a single component that combines multiple ICs, semiconductor die, and other discrete components within a unifying substrate. The MCM design approach enables designers to include a wide range of components on a single module by partitioning the system in order to realize each part with the best technology for the task. The die/packaged ICs and other components are then combined onto a single, multi-layered PCB module that contains all the interconnects, bias circuitry, filters and other passive components, and sometimes even a planar antenna. Consequently, MCMs offer superior performance for complex RF and microwave applications by including numerous implementation technologies within the same system. Design barriers for successful MCM design are being addressed by state-of-the-art electronic design automation (EDA) software tools, thanks to their expanding breadth and depth of capabilities, the speed of design flow, and the ease with which tasks can be performed. Nonetheless, MCM designers face several challenges for the successful design of their modules that are specific to EDA software. These challenges include the need to employ the best technology at hand for the electrical analysis/performance of the constituent parts, as well as electromagnetic (EM) analysis of the technologies, both within the module and for its associated interconnect. This task is most quickly and accurately performed in a design flow where the EM simulation can be done as an integral part of the process without having to launch a disparate third-party tool. With regard to the analysis of the MCM's constituent parts, the question that should be asked and answered is: What is the value of a multi-technology design flow? This white paper begins with this fundamental question, reviews the enabling technologies and their value for design, and then presents examples outlining a design flow for such modules that address not only EM analysis but also the electrical analysis of the various technologies encompassed within the module. A Module Design Flow In the absence of a single integrated design solution, designers in the past have still managed to bring modules into production, even high-volume production. Phased array radars, broadband receivers, and multiband mobile front-ends have all benefited in terms of cost and performance with module-based solutions leveraging multiple IC technologies and integrated PCB passives. In some cases, this design feat has not only included multiple IC technologies, but also several electrical domains of power: RF, analog, and digital. So, if modules of this sort can already be designed successfully, what is the upside to an integrated flow? Points of Integration as Elements of Risk One of the key tradeoffs in choosing a module solution over a complete IC, for example, is performance versus reliability. The ever-present drive for miniaturization within the semiconductor industry has resulted in smaller and smaller transistors with the ability to do more on the same size chip. The first ICs didn't necessarily replace discrete solutions because of size, but rather because the fewer points of integration between components led to higher reliability. Any number of things can go wrong when mechanically and electrically combining disparate components, and from a pure mean-time-before-failure (MTBF) calculation perspective, fewer parts means higher reliability. On the flip side is the consideration that if everything is implemented in one technology, then in theory only one or even none of the integrated functions is optimized. Designers choose a module implementation when performance must be optimized so that the best-in-class technology can be applied to each component in the design. However, this creates all the risks associated with multiple points of integration. Points of integration are naturally the die attach and bondwire or flip-chip bump connections that go directly into the MTBF calculations for the module, along with the actual MTBF of each component's functional lifetime. However, the module designer has an added risk that needs to be addressed when it comes to physical integration: fitting everything in the allotted space with proper clearances for manufacturing steps like pick-and-place heads, die attach, and wirebonding. The integrated MMIC/module design flow aids the design team by enabling the actual die, as designed by the team, to be brought into one project with the module itself and placed in that design and on that very module, a process called "in situ." Therefore, the bond pads or flip bumps that are aligned to down bonds or pads on the module are the actual structures and not representative footprints or "rep cells" derived secondhand from design artwork. The integrated module design flow EDA Software Design Flow Considerations for the RF/Microwave Module Designer 2

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