Book Excerpt: 'The Printed Circuit Designer's Guide to... Manufacturing Driven Design', Chapter 3

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Excerpt from: The Printed Circuit Designer's Guide to... Manufacturing Driven Design, Chapter 3: Why a Change is Needed

What Is Manufacturing Driven Design?
Manufacturing Driven Design is the process of providing full manufacturing awareness within the design process in a manner that allows designers to optimize a design for manufacturing with the first release.

MDD begins at the incarnation of the design idea. In the context of manufacturing, the initial step involves defining the material requirements for the stackup based on the desired electrical requirements. Once the material stackup has been established, the design layout can then be carried out. This simultaneously considers a manufacturer’s process capabilities as well as the traditional design rule check (DRC). A traditional DRC is mainly focused on copper or electrical spacing requirements and does not consider manufacturing needs.

Currently what we call DFM is not necessarily Design for Manufacturing; it’s Manufacturing in spite of Design.

This improved approach of MDD is already implemented in silicon wafer production, where the foundry’s production capabilities are taken into consideration right from the placement of the first pattern during design. This approach resulted from the skyrocketing cost of missing an assignment to a wafer production schedule and having to wait for the next opportunity. Imagine a PCB DFM release process that behaved in the same manner. Consider the financial and environmental savings if PCB manufacturers and design organizations took the same approach. The opportunity for overall PCB manufacturing and environmental improvement would be staggering. The environmental impact of excessive PCB production cannot be measured in the recovery of unneeded bare PCBs alone, but also in the extra board edge trim, wastewater—which contains copper, any number of stripping materials, tin, lead, and much, much more. Analyzing the environmental impact of PCB manufacturing is outside of this book's scope but should not be overlooked.

How Is MDD Different From DFM?
Design for Manufacturing today is seen as a step performed after the design is completed but before it is tooled for manufacturing. Often it is done with limited visibility of the applicable manufacturing partners’ process capabilities for that design technology.

Manufacturing Driven Design facilitates a more advanced level of collaboration, automation, and intelligence to achieve complete manufacturing awareness, surpassing the capabilities of DFM. In its ideal form, MDD covers all manufacturing details that can impact the yield, cost, or reliability of the PCB. It should include the following at a minimum:

• Fabrication process constraints 
• Assembly process constraints 
• Test process constraints 
• Actual PCB material stackup to be used 
• Assembly array and fabrication panel configurations

Very few manufacturers today provide their manufacturing process capabilities in a systematic, comprehensive manner to their design customers. Information is conveyed as requested, and only on the specific topic(s) at hand. Even then, it is communicated via email or a PDF of their manufacturing process capabilities specification—nothing that can be automatically acted upon within the design process. MDD provides the infrastructure to share all the necessary manufacturing process capabilities in an automated, synchronized method.

Carrying Capabilities Forward
Understanding the importance of MDD within electronics begins with the end. Ideally, manufacturing processes (fabrication, assembly, test) would be completed with the highest yield and reliability for the lowest cost possible. As the phrase “Manufacturing Driven Design” implies, the manufacturing process capabilities would be introduced at the beginning of the design process, which is carried forward throughout the process. Stated another way, a PCB design is constrained by not only the electrical requirements, but also by the manufacturing process capabilities.

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