Leveraging modular, multi-user DFM tools; achieving true verification of PCB manufacturing.

In today's electronics manufacturing market, profits are scarce, if existent at all. Lower sales also equate with significantly reduced capacity utilization due to insufficient volumes in manufacturing. The challenges of new product introduction (NPI) can exacerbate this problem even further. The requirement to provide fast time to manufacture, high reliability with low defects per million opportunities (DPMO) and the shortest time to market heightens core business challenges. To achieve these requirements for speed and quality, the NPI process must be optimized.

More efficient NPI processes allow contract manufacturers to compete for new products on the basis of how quickly they can move them smoothly into production. Advanced NPI services must include comprehensive design for manufacturability (DFM) for strengthening customer relationships, maximizing product introductions and optimizing profit margins. Original equipment manufacturer (OEM) customers quickly realize that electronics manufacturing services (EMS) contractors who are able to optimize the front-end of the manufacturing process can provide time-to-market and efficiency advantages that improve sales and gross margins. EMS companies receive advantages of lower implementation risks, higher levels of profit and increased customer satisfaction with quality, on-time delivery.

The various methods for assessing manufacturability range from manual inspection of design files to fully automated analysis. Given the limited capital resources of today, selecting the best DFM solution in terms of fast return on investment (ROI) can be tricky. A complete DFM approach consists of a number of distinct but interrelated segments. These include design for fabrication (DFF), design for assembly (DFA) and design for test (DFT). Also, keep in mind that DFM cannot be adequately applied to a particular product design without also taking into account the real world production environment in which it is to be built. Even if a DFM program addresses generic printed circuit board (PCB) assembly issues, such as inter-device clearances and spacing for pick-and-place nozzles, it still is not adequate unless it relates those generic issues to specific production requirements.

Cross-Organizational DFM Benefits

For EMS providers and their customers, DFM has far reaching benefits that go well beyond just the ability to optimize a particular design. Over time, the DFM process becomes a key tool for on-going communication between the EMS company and their customers regarding issues such as conformance with design rules, definition of best practices and evolution of production capabilities. As the EMS provider develops a full library of detailed DFM scripts that define its process and factory-specific operations, its customers' design groups are better able to plan ahead for optimizing the targeted manufacturing environment(s). Through the iterative application of a DFM discipline, the gap between design processes and manufacturing processes can be continually narrowed, resulting in fewer discrepancies, smoother manufacturing handoffs and faster time to market.

Another major benefit of the comprehensive DFM approach is the ability to capture core knowledge sources regarding manufacturing processes and to extend that knowledge across the entire organization. During the difficult economic period that has impacted the electronics industry over the past few years, both OEMs and EMS contractors have lost a significant amount of historic knowledge through the process of downsizing. Adherence to disciplined DFM practice will retain this knowledge base and also organize it for maximum accessibility.

The Bottom Line: Tangible ROI

As with any production or design tool, the bottom line centers on how quickly and in what ways the investment will pay for itself and generate a positive return. For both the EMS company and its customers, the payback from DFM comes immediately in the form of reduced cost for breaking new products into the production line. By modeling an accurate match between the product design and the specific production line, corrections can be made prior to release rather than incurring the high costs and delays associated with prototyping and correction of problems on the production floor.

For example, even a relatively simple change such as improving accuracy of fiducials has been shown to increase placement accuracy, with resultant decreases in rework of as much as 10%. Another common example involves spacing between through-hole pins and surface-mount pads, which can cause cross-wicking of solder and shorts under the surface-mount components, resulting in costly rework requirements. Since ultimately these costs have to be passed back to the customer, any savings can immediately accrue to both the contractor and the OEM.

In the final analysis, shortening overall time to market is probably the most important return on investment in DFM. While production inefficiencies and rework can add significant cost, the inability to successfully launch products within today's tight market windows and competitive environment can ultimately mean the difference between overall success and failure.

Benefits to Design

By painting a complete and accurate picture of assembly and test parameters, a comprehensive DFM system gives designers an accurate roadmap for moving their designs smoothly into production. The result will be faster and more efficient product launches with accelerated time-to-revenue. The benefit to designers is that schedules are secured because redesign is not needed.

In outsourced situations, the DFM architecture needs to provide flexibility, modularity and ease-of-use to enable designers and production engineers from different companies to view shared DFM data and to efficiently communicate regarding design changes and correction of discrepancies. Coordinating all of these issues can be difficult even when the design and production groups are part of the same company. However, the effective implementation of comprehensive DFM processes is especially challenging for an outsourced EMS environment.

Establishing DFM objectives

From the perspective of a provider of electronics manufacturing services, a DFM system needs to address four fundamental questions to deliver true verification of manufacturability. These questions are:

Overview of a Modular DFM Architecture

An advanced DFM architecture uses a modular segmentation approach that combines a proven analysis engine with specific modules targeted at defining DFM tests, running the tests and visually exploring and analyzing the resultant DFM data. This modular approach provides a highly efficient data flow. The system would have direct access to the design database of ECAD information in its native format and can analyze the design's manufacturability against specific manufacturing parameters contained in the DFM script files. The output of this analysis is a complete set of DFM results (.cc files) in a database that can be selectively accessed and analyzed by many different users.

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This modular architectural approach allows manufacturing process engineers to create detailed pictures of their specific production environments to drive the analysis process for verifying the manufacturability of any proposed design. Because script files can be saved, reused, combined and modified using a point-and-click interface, users can quickly configure a tailored, factory-specific DFM analysis process for each new design.

By using parameter-driven attributes, programmers can efficiently create thousands of different combinations for defining specific DFM scripts. For instance, the user could select package-to-package spacing tests, define specific series of tests for different package types [such as chip-to-ball grid array (BGA) and chip-to-quad flat pack (QFP)] and then assign specified clearance criteria for components within each combination. The point-and-click interface makes building up a variety of package-to-package relationships that reflect each production line's specific operational capabilities easy. Any of these test parameters also can be saved for ready availability when creating new DFM scripts. As the library of DFM scripts grows to reflect all of the operational specifics of the production facility, adapting scripts for new designs and/or for new operational capabilities also becomes an easy incremental task.

For multi-facility manufacturers, specific script file libraries can be developed for each production line and also can be used to help support migration of products and best practices between different production facilities. For example, an EMS provider can give a customer feedback on which facilities are most suitable to build a specific design and/or can provide detailed design modification suggestions that could enable it to be built across all facilities.

At run time, the system would give the user complete control over the DFM analysis process that is used to generate the DFM .cc files. Depending upon the printed circuit assembly (PCA) design being evaluated, various DFM scripts can be concatenated together and executed at the same time using a simple load and run process. For quick, focused analysis runs or to skip over known problem areas, the user also can selectively enable or disable individual tests within a script for the current execution cycle, without having to actually modify the underlying DFM scripts in the library.

The final element would be a Windows-based freeware viewing application that allows users to visually access the analysis results. An ideal viewer could run on almost any Windows PC environment with minimal resource usage and no special hardware or software requirements. Users should be able to remotely access, navigate and analyze the DFM .cc files in either text format or rich visualization formats.

The key to effective usage of DFM analysis lies in providing clear, accurate and timely information to design engineers so that the PCA design can be optimized for the target manufacturing environment. The above described architecture focuses on maximizing availability of the DFM data to design engineers by eliminating traditional economic and technological barriers to providing widespread access. For EMS providers, this technology means that their customers can have easy-to-use, no-cost access to the DFM data. As a result, comprehensive DFM services can be integrated as a seamless and routine part of the customer relationship.

* Can I build it?

* Can I test it?

* Can I repair it?

* Can I share it?

By addressing all of these questions up front with the customer during evaluation of each new design, EMS providers can identify any critical obstacles and also can get a much better picture of the projected cost of building the product. In many cases, the use of DFM to verify and finetune the design prior to beginning production can deliver very significant return on investment by avoiding multiple rounds of design and prototyping, reducing start-up problems, improving yields, minimizing rework costs and/or enabling the product to be produced across multiple production lines.

Architectural Elements for Effective DFM

A DFM system must link data from design through manufacturing, while addressing the specific requirements of a given environment. DFM must also promote communication across design, manufacturing and management, providing closed-loop feedback for improving a design's manufacturability. To accomplish these objectives, the DFM system must be able to:

* read electronic computer-aided design (ECAD) data, preferably from a variety of sources

* have standard and configurable menus to define tests to be performed

* provide output results that give statistics and alarms where desired

* be able to share the data across locations and functional disciplines with capability for adding comments, questions and suggestions.

Implementation of a DFM system lends itself to the use of a modular architectural approach because it allows the various functions to be tailored for the most efficient use of resources, while simultaneously allowing maximum flexibility for distributed access by many users in different locations. For example, the definition of manufacturing parameters and the running of DFM analysis programs would likely be handled by a relatively small group of production engineers; however, the resultant DFM data needs to be made available in visual format to many product design engineers for further analysis and feedback (see sidebar).

For EMS providers, this practice means that all of their customers can have fast, user friendly, no-cost access for viewing, commenting and analyzing the specific DFM data generated by the DFM process. As a result, communication about issues, costs, risks and opportunities that impact efficient manufacturing implementation can be effectively facilitated.

The ultimate goal of a DFM system is to help design engineers optimize PCB designs for efficient manufacturing within the practical limits of real world processes. This result can only be accomplished through seamless sharing of detailed DFM analysis data via an easily accessible and readily understandable process that promotes feedback and facilitates design updates in the shortest possible timeframe. Today's DFM architectures can simultaneously increase the quality of data available to design engineers while streamlining remote access and overall usability of the DFM information. The outcome is improved profitability and competitiveness, an edge that any company can use in today's environment.

Chris Czernel is director of applications support with Router Solutions Incorporated, Newport Beach, CA; email: [e-mail], and Jeff Cealey is operations development project manager with Jabil Circuit, St. Petersburg, FL; email:[e-mail].