As an engineer, you may have faced the challenge of explaining what you do to friends or family members who are not technically inclined, only to imply marginalization of the difficulty of what you do. However, those in the industry know all too well the technical aspects of designing PCBs. Although the process of PCB design brings forth comparisons to a jigsaw puzzle, it is no game.
PCB development always begins with the end goal in mind: production. However, the feasibility of PCB production depends on developing a design that meets the standards necessary for manufacturing. One of the most important and far-reaching aspects of PCB design is component placement. Component placement impacts all design decisions on a PCB; and by following good component placement guidelines, you can design boards that can be manufactured accurately and efficiently, without the need for additional cost, correction, or rework.
PCB Component Placement Guidelines for Manufacturing
If you were to ask any engineer, they would probably attest that following design for manufacturing (DFM) guidelines is a critical step in the PCB development process. DFM involves designing for the ease of production of a product’s integral components. In general, DFM focuses on selecting the most economical and durable materials and processes to facilitate the manufacturing process.
Design decisions, largely governed by DFM in the PCB world, determine nearly 70% of all manufacturing costs for a device, i.e., processing, assembly, and cost of materials. In fact, production decisions, like machine tool selection or process planning, are only responsible for approximately 20% of the cost .
The primary objective of PCB development is to design a PCB that functions and performs as intended. However, it is equally, if not more, important for a design to be manufacturable. Of course, various determining factors may affect PCB manufacturability, including:
- Components: If a component is distinctive or challenging to acquire, it will increase the cost of manufacturing. Moreover, if the lead times on some components incur delays in production, it will increase costs.
- Placement: Component placement affects how you manufacture a PCB and whether you can even manufacture a PCB. Improper component placement can dramatically increase board costs. In fact, design decisions as simple as the orientation of a component can affect its solderability.
- Layout: The schematic layout places component placement and other considerations at the center of your design process. However, failure to account for possible connections or interfaces with other PCBs will increase overall system manufacturing costs.
Why DFM Should be a Top Priority
In regards to printed circuit board design, DFM is a critical task that can help prevent errors, aid manufacturability and reduce development time. The following are examples of the types of mistakes one can avoid when utilizing DFM:
- Errors in component placement: Placing components too close to one another, improper orientation, or the incorrect location will result in issues during the soldering process.
- Incorrect footprint design: If the footprint does not match the actual component to be mounted a number of issues can arise. For example, traces that do not match the pad size can result in lower current or signal integrity problems. Additionally, if the component is not positioned well on the pad it may lead to a bad solder joint on one side that disconnects. This is called tombstoning.
- Insufficient spacing between components, the board’s edge, and other mechanical objects: Mistakes of this nature creates issues in assembly (automated) and in the possible rework (manual).
- Solder mask slivers and copper: There are times when small slivers (solder mask or copper) flake off during reflow. These slivers will float from one location to another and reattach to the board. Furthermore, if that is the case, and it is copper, it can create shorts between other traces. Moreover, a freely moving (flaked-off) solder mask can expose the board and may ultimately lead to oxidation.
DFM Guidelines to Optimize Component Placement
For a more efficient PCB assembly process, here are a few guidelines to follow:
- Optimize the placement of PCB connectors in reference to interfaces and other system-level boards. Also, be sure to allow enough room for unplugging and plugging of cables during assembly.
- Whenever possible, place all surface mount technology (SMT) components on a single side of the PCB to reduce costs.
- Abnormal sized or taller components will create issues with soldering, and you should avoid placing smaller (SMT) components near these components.
- You should also avoid the placement of components to close to the edge of the board. This will reduce issues when removing or breaking these PCBs out of their panels.
- If wave soldering is used, orient components to promote good solder flow and to accommodate fixtures, if necessary.
Because component placement affects every aspect of PCB design and manufacturing, including assembly time, reliability, and functionality, it should be at the center of all design decisions. Assessing and correcting component placement errors can be an arduous task. To maximize the benefits of DFM, consult your contract manufacturer (CM) early in the PCB development process.
|Tempo's Custom PCB Manufacturing Service
At Tempo Automation, we partner with you from day one of design to maximize the benefits of DFM for product development, including making the right component placement decisions. With our digital thread process, we offer an unparalleled level of speed and precision.
And to help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.
If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on PCB component placement or how to optimize it for PCB manufacturing, contact us.