PCB Assembly Considerations
Decisions about component selection and layout composition can increase assembly costs and the time-to-market.
PCB assembly considerations involve making careful design choices.
Modern EDA software capabilities can reduce PCB assembly issues.
PCB assembly considerations include selecting quality components, choosing the right layout, and leveraging EDA software capabilities.
When looking at the results of different surveys about why electronic products fail in the marketplace, several trends become apparent. In some instances, design teams attempt to solve non-existent problems or over-design a product with the assumption that consumers want more features. The decision to over-design may cause them to run over budget and encounter supply chain problems.
This issue illustrates the need for designers to carefully contemplate important PCB assembly considerations and design for assembly principles before they jump into the fabrication process. The selection of quality components, the right layout, and EDA software can mean the difference between a successful project or a costly failure.
PCB Design Choices Impact PCB Assembly Considerations
Design teams need to consider DfA principles when designing PCBs
PCB assembly can fall prey to the same problems that prevent good ideas from becoming successful products. To avoid these problems, design teams should apply the principles behind design for assembly (DfA). Considering DfA principles when assembling a PCB will ensure design teams make thoughtful decisions that decrease the lead time needed for a project, minimize risk, and mitigate issues that can result in costly revisions.
Design for assembly affects how designers choose components, select suppliers, and work with fabricators. Additionally, DfA drives decisions regarding PCB layouts. DfA principles involve making PCB design decisions about functionality, efficiency, and cost, and each factor has a direct impact on the form, quality, and reliability of the completed product.
The table below details the key points of consideration that DfA addresses:
Design for Assembly Principles Makes PCB Assembly Easy
The primary objective of DfA is ease-of-assembly. Moving towards that objective requires an emphasis on eliminating complexity and reducing uncertainty. An emphasis on eliminating complexity pushes design teams to think about reducing the number of components used for a PCB and to consider the type of components selected. For example, design teams may determine that selecting resistor or capacitor arrays—rather than groups of single passive components—saves board space and lowers costs.
The “back-to-basics” approach to DfA also prompts design teams to consider—and perhaps reconsider—the use of fragile, heavy, or bulky components. Heavy and bulky transformers, power resistors, and mechanical assemblies drive shipping costs higher and require specific fabrication measures to ensure that the physical design of the board supports the components.
Fabricators are assisted by the decision to reduce the number of components, as fewer components mean that fabricators require less pick and place passes for their equipment. The use of standardized, common components also decreases the number of reel changes for fabricator equipment. Although fabricators recognize that product design may require a special component package, the use of unique packages can introduce delays in the production process because of fabricator requirements for comparing the PCB layout with datasheet footprints for each component.
DfA requires attention to decisions about the PCB layout. Choosing to rely on vias-in-component pads or wire harness assemblies may initiate a ripple effect that impacts stability, time, and cost. Because the reflow process for via-in-component can allow tin to leak, fabricators take the additional time and cost to fill vias-in-component pads with epoxy. Rather than use wire harness assemblies that can increase costs and lead time, design teams should consider modular designs or different interconnection options. If a PCB design stipulates wire bonding or conformal coatings, fabricators require mask drawings that show the areas designated for the finish or coating.
EDA Software Eases PCB Assembly Considerations
An emphasis on standard components eases concerns about the ability of fabricators to procure parts. Many EDA software packages include component libraries that connect the PCB design team with reliable manufacturers and known inventories.
Modern EDA software also improves the consistency and clarity of Gerber files, assembly drawings, and Bill-of-Materials. This emphasis on consistency and clarity reduces time-to-market by ensuring fabricators that documentation includes all design revisions. The capability of EDA software to generate a BOM from the schematic and reference notes also speeds the assembly process. While fabricators continue to manually review the BOM, the capability to eliminate incomplete, inaccurate, or missing component numbers or mismatches between part numbers and descriptions saves time and reduces costs.
PCB assembly considerations include the selection of quality components, an excellent layout, and quality EDA software—find the resources you need for all of this and more on the PCB Design and Analysis overview page. The latest products and solutions from OrCAD PCB Designer can help you achieve your next great design.
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