Design for Manufacturing: Contemplate, Anticipate & Optimize Your PCB

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Design for Manufacturing: Contemplate, Anticipate & Optimize Your PCB

Posted by: aeadmin
Category: Technical Posts

A critical success factor in your product development journey is optimizing the design for manufacturability (DFM) aspect of your Printed Circuit Board (PCB). Decisions you make at the design stage can have major repercussions on the cost and efficiency of your manufacturing process.

What is DFM?

Design for manufacturability (DFM) is the scientific practice of designing products in a manner that makes them easy to manufacture for medium to high-volume runs, as well as for low-volume environments where non-recurring engineering (NRE) may be reduced. DFM optimizes fabrication, assembly, test, procurement, shipping, delivery, service, and repair.

While generating a prototype is an exciting stage in the product development cycle, a prototype is not ready for manufacturing. To manufacture the prototype in large volumes, engineers have to determine the steps for repeat production with consistency and efficiency. This is where DFM comes in.

A prudent DFM strategy can shorten the product development time, reduce rework and repair costs, ensure on-time launch of your product as well as high-quality production.

Design for Manufacturability also demands meticulous documentation, from assembly to test procedures.

With specific regard to PCBs, the first build will be smoother with a good DFM strategy that defines design guidelines and best practices for manufacturing.

Considerations for bare PCB DFM

Considerations for bare PCB designs are almost endless. It’s best to start with the end in mind to define your priorities and engage your EMS partner early in the design process so that your design can be easily translated into a manufacturing environment.

Here is a quick technical rundown of some of the common things to bear in mind while designing your PCB for manufacturability. There are many other considerations than what we’ve identified below, however each product is unique and requires special consideration depending on your unique manufacturing requirements.

Bill of Material (BOM) & Manufacturer/Component Selection

Using commonly-available and standard materials can help to reduce lead times as well as the probability that your selected materials and components will be discontinued. Whether you require a full turn key or consigned build, it is important to identify all approved manufacturers on your BOM to reduce any confusion during the production set-up. Provide complete kits with spare components for any consigned builds, as there is typically a 2 to 5% dropout rate during manufacturing.

Providing your Contract Manufacturer with a complete BOM and all of the necessary PCB specification files and drawings reduces setup time, and increases the set-up efficiency particularly with New Product Introductions (NPIs) and prototypes where you want quick turnaround.

Panelization & Depanelization

Involving your Contract Electronics Manufacturing (CEM) partner early on in the panelization approval process makes for more efficient production, especially if full traceability of all unpanelized boards is important to you. If your product does require traceability or the ability to link each PCB to their parent assemblies, ensure your PCB designers designate an area for a barcode. This is something that is typically overlooked by product designers.

The two most common panelization methods are V-Score (also known as V-groove) and tab routing (also known as breakaway tab). V-Score panelization is typically preferable as it is more structurally sound and offers less chance of sagging in the reflow oven and wave-solder machine. It is also less likely to accidentally break out of the panel. However, the V-Score method is not suitable for board designs with overhanging components, as these components can be damaged during depanelization. Tab routing is a more fragile method, requiring careful engineering and handling to ensure quality. While tab routing is advantageous for non-rectangular shaped board designs and boards with overhanging parts, it also has a higher possibility of issues during the depanelization process.

Another good rule of thumb is to ensure every panel has breakaways around it, and it is ideal to have them all the way around the board with a minimum clearance of 10mm. Allowing adequate space helps prevent damage to the board or components allowing for conveyor edge clearance and more flexibility during automated processing.

Altering the number of PCBs per panel is a multi-variable cost optimization strategy that should involve your CEM’s professional analysis.

Component Placement, Board Layout & Design

Solderability: ENIG electroless nickel gold improves the solderability of a flat surface giving it a better quality finish than HASL finish which can create solder balling. VIAs within pads that require soldering should be plugged to avoid solder starvation or second-side/print related processing issues.

Fiducials: Each PCB should have a minimum of three fiducials to locate the board for proper placement accuracy and flexible processing. PCBs in a panel should typically have three fiducials on the panel plus three on each PCB within the panel.

Polarity: Use silk screen polarity indicators to identify all components that have a polarity.

Wash Proofing: Some PCB components are wash proof, however many PCB components are not wash compatible. It is important to notify your CEM about parts that are not wash compatible, so you can avoid potential costs to rework these parts.

Conformal Coating Considerations: Just like wash proofing, the performance of some components is adversely affected by certain coating materials or the curing process. A good example of this is image sensors or optical pickups, which can be impacted by the UV curing process.

It is also important to identify if mounting holes should be coated or left uncoated. Typically it is best practice to leave any electrical connections uncoated, to avoid any impact to their intended function. Involve your CEM early in the product design process to determine the appropriate coating materials and curing methods for your product and its end use.

These are some of the common concerns to plan for when you want to design for manufacturability.

Whatever your decision as an OEM, when you consider your next contract electronics manufacturing partner, it is important to involve them early on in your process so that your product is designed with the manufacturing process in mind. for manufacturability.

At August, we have comprehensive experience in optimizing your product design for streamlined builds, reducing inefficiencies and unnecessary rework in your manufacturing process. Please check out this link for a primer on how August plays a strategic role in ensuring Design for Manufacturability (DFM) for your products.

If you would like to explore our DFM services or just bounce ideas, contact us today.