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Editor’s note: The following article is an excerpt from Chapter 5 of the I-Connect007 eBook The Printed Circuit Designer’s Guide to… Documentation, written by Mark Gallant of DownStream Technologies.
Most EDA software providers have enhanced their tools by integrating new functionality and broadening their offerings through acquisition. Core EDA tools—including schematic capture, digital and analog simulation, PCB design, autorouters, and many others—have matured and have dramatically reduced time to market. However, implementing automated features for creating PCB documentation has been largely ignored by PCB CAD tool providers. As a result, PCB CAD tools are inherently inefficient for the final and critical phase of the PCB design process—creating documentation.
Creating comprehensive PCB documentation is a requirement in all electronics companies. If the end product is destined for a military or aerospace user, the documentation requirements increase considerably. Even in applications where accurate documentation is critical, much of it is created using CAD drafting features that have not improved since the CAD revolution of the 1980s. PCB CAD tools are superlative at reducing the PCB design cycle but fall short on some of the most basic documentation tasks.
For example, PCB design tools selling for tens of thousands of dollars per seat lack basic spellcheck features found in a $99 word processor. Most PCB CAD tools lack support for a paragraph requiring the creation of multiline text strings for fabrication or assembly notes. Countless hours are spent using rudimentary drafting tools to create layer stackups, PCB detail views, or drill charts one segment or line at a time.
These antiquated documentation methods impede the drafting workflow most often during a design re-spin. Drill quantities out of sync in a manually drawn drill chart? Select the text string and edit the value. Layer stackup changes? Manipulate the layer graphics and text to update the stackup. Does the PCB detail view need updating because a component moved on the PCB? Either recapture the entire view or start editing the graphics one vertex or one segment at a time. All of these manual updates are time-consuming and subject to human error.
Engineering organizations that use popular MCAD tools to complete the PCB documentation have additional encumbrances. MCAD tools are usually superior to ECAD tools with respect to creating documentation. However, the conversion of the design to MCAD file formats results in disassembling of the intelligent ECAD data. Part outlines are converted to shapes, traces to lines, copper shapes to polygons, etc. Creating tables, notes, and complex dimensions is certainly quicker in MCAD, but gleaning intelligent data for a parts list is mostly impossible. Should a design re-spin be required, the MCAD drawings must be recreated or manually updated with new design content. This drawback also introduces an MCAD design database to an already overcrowded PCB documentation file collection. Maintaining synchronicity between PCB and MCAD design databases wastes valuable designer time.
There is a hidden cost to performing a task inefficiently. If that task is repeated often enough in the engineering process, the inefficiency will have immeasurable costs for time-to-market delays on new or updated products. Every PCB design has its share of tasks related to documentation. Some documentation sets must include dozens of drawing sheets. Stringent documentation standards for military, aerospace, automotive, and other products require highly detailed, time-consuming documentation sets.
PCB documentation requirements are not limited to a single department’s needs. Documentation requirements are unique for each entity that comes in contact with a completed PCB design. Many downstream processes in product manufacturing have unique documentation requirements, including PCB rework instructions, assembly process steps, PCB panel fabrication drawing, assembly inspection, and more. As previously presented, there is more to a PCB documentation set than single-sheet assembly and fabrication drawings. Let’s consider the following scenario as a means to measure the cost of document creation inefficiently. "PCB documentation requirements are not limited to a single department’s needs."
A new product’s documentation cycle begins at the prototype stage. From this first stage, the number of documentation iterations can easily reach double digits. Consider that each iteration of a documentation set has both tangible and intangible costs—the greatest tangible cost likely being the salary of the individual creating the documents. Let’s assume a PCB designer’s annual salary is $100,000, and 20% of their time is devoted to inefficiently originating documentation. Creating documentation could cost an organization an average of $20,000 per PCB designer. Developing military-standard PCB documentation requirements can usurp more than 50% of a PCB designer’s time. For those types of electronic products, the cost of creating and maintaining documentation in an inefficient, traditional manner can easily escalate.
There are also intangible documentation costs that can be difficult to quantify. An inefficient documentation process that results in delays to new product introduction may have lost opportunity costs. Errors in a documentation set may result in multiple unplanned documentation revisions. Having a PCB designer focus on documentation rather than PCB design will delay the start of the next PCB design project. Sharing a networked software product license to create documentation and design PCBs may require users to postpone critical tasks until product licenses are made available. If other tools are in use—such as AutoCAD, Visio, or Microsoft Excel—to assist in creating documentation, the cost of training, owning, and maintaining those systems on an annual basis is also part of documentation expenditure.
When considering the cost of a PCB documentation method, it is important to measure both the creation and maintenance of a complete documentation set for the full life cycle of the product. Creating an initial documentation set will likely result in the bulk of the cost, but maintenance can be time-consuming as well. All of these documentation requirements ought to be part of any documentation efficiency calculation.
To read the rest of The Printed Circuit Designer’s Guide to… Documentation, click here. Visit the I-Connect007 eBook Library to download this book and other free, educational titles covering everything from high-speed PCB design to advanced manufacturing and assembly.