Printed Circuit Design & Fab - December 2007 - (Page 40)

DfM The Critical Parameters in the DfM EQUATION A successful DfM program is part methodology, part design environment and part toolset, with a foundation based on fabrication processes. by NOLAN JOHNSON If you’re an engineer designing electronics systems for anything other than pure R&D bench work, this is what you do: design, redesign, simulate and, ultimately, manufacture your product – all while balancing the many sets of simultaneous constraints (target component costs, form/fit/finish, compliance, complexity, reliability, etc.) to deliver a robust, innovative and profitable project. DfM (design for manufacture) is about creating the detailed documentation necessary to deliver accurate, easily reproducible end products. DfM is also about hitting the center of your allowed process windows so a process deviation doesn’t end up ruining your yield. DfM has been an active, ongoing topic of discussion in other CAD/EDA sectors, such as semiconductor design. In a recent industry white paper, semiconductor software firm Synopsys (Mountain View, CA) made the following observations: “Design for manufacturing is about connections … connections within the design flow; connections within the manufacturing flow; and, most importantly, connections between design and manufacturing. These connections are required to address fundamental issues associated with yield loss in today’s leading-edge … products and are key to a robust DfM solution.” FIGURE 1 illustrates the point: each step in the design and manufacture of your project has a process window. Your project’s ultimate process window for DfM purposes is the intersection of all the process windows in your design flow. Design for Manufacture: Where It Fits in the Design Flow Historically, implementing a DfM protocol for your design team has been a largely human endeavor, built up from expert knowledge, practical understanding and a collaborative engineering culture (FIGURE 2). While the human portion of DfM persists, it is no longer sufficient. PCB design tools have been available on the market almost since the dawn of the CAD/EDA industry. Exactly when PCB design rule check (DRC) and DfM tools emerged onto the marketplace differs depending upon which tools you include, but the general consensus is that DRC/DfM checkers for PCBs were available by the late 1980s. This begs the question: if DfM has been around so long, why the sudden spotlight? Perhaps the answer lies in the culmination of everincreasing design complexities, shorter design cycles and the increased levels of outsourcing for design and manufacture that have created the “compelling event” for DfM. Therefore, DfM is part methodology, part design environment and part toolset. In other words, successful DfM is influenced by the workflow process being followed. The realization is that a true DfM solution must be holistic; it must include the design team, manufacturing supply chain, and test and component suppliers all together in a single design and manufacture ecosystem. This is exactly where traditional PCB DfM DECEMBER 2007 Designer Fab Actual Fab as Published Process Window Assembly House FIGURE 1. Supply chain misalignments in the process window can shrink the projects overall process window. 40 PRINTED CIRCUIT DESIGN & FAB

Table of Contents Feed for the Digital Edition of Printed Circuit Design & Fab - December 2007

Printed Circuit Design & Fab - December 2007 Contents Our Line Market Watch Around the World Happenings ROI 2007 PCB Designer Salary Survey Interconnect Strategies Positive Plating RF Design Ad Index Noise Reduction Supply Chain DfM Off the Shelf Marketplace The Signal Doctor

Printed Circuit Design & Fab - December 2007

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