Aug. 18, 2025
Every PCB should be designed in such a way that the overall cost and chances of potential DFM (design for manufacturability) issues can be minimized. It is a process of arranging the PCB layout to resolve problems that may arise during fabrication and assembly.
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DFM checks each design before the files go for fabrication. It will point out the potential defects in advance and ensure the boards are manufactured to the exact specifications.
Optimizing a board to avoid fabrication issues creates the requirement of design for fabrication (DFF). In the same way, circuit board assembly problems can be avoided by integrating a comprehensive design for assembly (DFA) checklist.
DFM is the amalgamation of these two processes, which is used for turnkey boards (both fabrication and assembly).
Highlights:
For reliable high-speed PCBs:
In this blog, you’ll learn 5 common DFM issues you should watch out for and techniques to avoid them.
DFM for circuit boards is a set of design guidelines that attempt to ensure its manufacturability. Imagine finding issues in the fabrication and assembly process in the final stage.
That would be a nightmare! DFM is not only a manufacturer’s guide to better fabrication and assembly, but it can also help you. It’s true that fab houses use this to check for issues and fix them. It also provides a common ground for you and the manufacturers to make the relevant design changes.
When done correctly, DFM helps you:
When you run a DFM check, you get:
This approach is often called manufacturing-driven design.
Consider these DFM parameters before finalizing your design:
According to Oren Manor, Director of the Siemens EDA Business, both designers and manufacturers should be involved in DFM checks. Here’s how each side benefits:
Manufacturers run DFM to:
As a designer, DFM helps you:
Running DFM early helps make sure your PCB design matches the manufacturer’s capabilities, reducing the risk of fabrication defects.
It’s important to distinguish design for manufacturing from design rule check (DRC), as they serve different purposes:
What DRC does
DRC checks whether your design meets a set of predefined rules, usually set by the design tool or based on generic industry standards.
However, DRC doesn’t consider the actual manufacturing process.
What DFM does
It checks your design against manufacturing capabilities and constraints.
Here’s how DRC and DFM differ when it comes to key manufacturing constraints like annular ring and drill-to-copper spacing:
Running PCB design for manufacturing checks only at the end of the design is common, but inefficient.
Late checks often lead to:
Instead of waiting until the end, you can run targeted DFM checks at different stages of the design process, such as:
Oren Manor explained, You don’t need to run all the design for manufacturing checks for PCBs every time. Instead, run 10–20 relevant checks during each stage. This allows you to catch and fix issues early, when changes are still quick and inexpensive to make.
If a PCB is performing appropriately and the design engineer is also satisfied with it, then why do DFM checks? The answer to this question is to optimize the cost of the final circuit board and eliminate potential design failures.
Check out our infographic on 8 common DFM Errors and Ways to Avoid Them.
Avoiding DFM issues is a better approach than letting them ruin your circuit design and then looking for a remedy. Checking for manufacturability is a smart move from your side. It solves problems before they appear. The issues in the design can be due to:
Keeping track of design rules and performing consistent checks can help you avoid the following DFM issues:
Slivers are small, free-floating wedges of copper (conductive) or solder mask (non-conductive) on the plane. These can get redeposited to other copper pieces or exposed copper to create shorts.
If they are big enough not to float, then they form an antenna, responsible for noise and other interferences within the board. Now, the question is, why do they create an antenna? Because they have no grounding, they act as a signal catcher.
How to avoid copper slivers? Slivers can be avoided by maintaining copper features around 0.004 inches. In the example given below, we are talking about the spacing between antipads.
This trick is not 100% foolproof, but it greatly reduces the chances of copper redeposition elsewhere on the layer. This depends on the copper weight. The higher the copper weight, the wider the connection area required.
To learn about prevalent solder resist defects, see 6 common solder mask errors every PCB designer should know.
Thermals are the small copper spokes in a thermal relief pad, used to provide sufficient heat for the soldering process. The spokes actually prevent the heat from dissipating, which helps create a robust solder joint and an accurate electrical connection between the pad and the plane.
In some cases, voids between the thermal and the plane or the pad can lead to an incomplete connection, minimizing the heat concentration required to form a proper joint. This, in turn, can lead to various functional problems.
Such thermals affected by voids are called starved thermals. This may solder irregularly or take a longer time to reflow during the assembly process.
Thermal performance directly affects board reliability. Use these techniques to efficiently dissipate heat in high-power designs:
If your design includes thermal vias in ground slugs, discuss with your PCB supplier whether to cap or plug them based on their manufacturing capabilities. Once confirmed, collaborate closely to implement them correctly. This early alignment ensures thermal reliability without causing delays during fabrication.
For more heat dissipation techniques, see 12 PCB thermal management techniques to reduce heating.
Pins (plated through holes) that are missing a clearance pad will connect to a plane layer. If clearance pads are unavailable from all plane layers for the pin, it will connect all of the voltage planes.
Drill size is specified that exceeds the annular ring size being drilled, and can result in a disconnect of the pin or short in a voltage plane.
Sometimes, insufficient clearance is provided between the copper and the PCB edge. If copper is too close to the edge, then shorts can be created when current is applied to the panel between the adjacent layers. It happens due to the exposed copper around the perimeter of the board.
Design tip: DFM issues can be avoided by following DRCs for DFM checks.
DFM checks are mandatory for designing a PCB with optimum manufacturability. This can save you from the disastrous effects of potential defects.
The hole drilling process is the foundation for vias and the connectivity between different layers. It is the most expensive, irreversible, and time-consuming step in the PCB manufacturing process.
As soon as the number of holes increases, the check for drill-to-copper spacing becomes critical. Two significant aspects to be considered in the drilling process: aspect ratio and drill-to-copper clearance (drill to the nearest copper feature).
1.1 Aspect ratio (AR): The ideal aspect ratio is 10:1 for through holes and 0.75:1 for microvias. When the aspect ratio is larger, it becomes more difficult to achieve reliable copper plating inside the vias.
It will also add to the time for manufacturing and cost. Hence, the smaller the aspect ratio, the higher the PCB reliability. At Sierra Circuits, we offer an aspect ratio of 0.75:1 for microvias.
AR (Through-Hole) = [(Thickness of the PCB) / (Smallest drilled hole)]
Since microvias don’t protrude through the entire board, the aspect ratio would be:
AR (Microvias) = [(Drill Depth) / (Smallest drilled hole)]
1.2 Drill-to-copper: It is challenging because different process tolerances impact it throughout the manufacturing process, which includes:
Achieving tight drill-to-coppers requires X-rays into the inner layers to get scaling information after lamination. Always check if your fabricator has that capability. To learn more about voids in lamination, read lamination voids and delamination in PCB manufacturing.
How to handle drilling disaster: Problems like roughness inside the drill hole, resin smear, burrs, and nail heads can be avoided by adopting deburring and de-smearing processes.
Maintaining clearance between vias and nearby planes helps prevent unintended short circuits. This is also important in high-frequency applications where unwanted coupling between the via and the nearby plane can lead to signal integrity issues.
Accurate hole placement is essential to ensure robust electrical connectivity and layer registration. The typical tolerance for drilled holes is ±3 mil, and for routed slots, it is ±5 mil.
The required clearances depend on the material used in the stack-up, whether it’s homogeneous or hybrid. Assuming a homogeneous stack-up with FR-4 material and an aspect ratio of 10:1, for 4, 6, and 8 layers, a 6 mil drill-to-copper clearance is needed.
For 8, 10, and 12 layers, a clearance of 7 to 8 mil is necessary. Plane-to-plane spacing varies based on the copper weight; for 1 oz, 5 to 6 mil is preferred, and for half oz, 4 to 5 mil is suitable. Also, have at least 6 mil drill-to-drill spacing to maintain structural integrity.
Further, ensure adequate capture pads for laser-drilled vias. Have a capture pad diameter of 4 mil more than the drill size.
Annular rings are one of the biggest concerns while designing a PCB. Even if you have placed a via right in the middle of the pad in the design files, it might not be easy to get the same result in the physical world. Even though you calculate and place the perfect annular ring in their CAD design, manufacturing issues often cause vias to be drilled off-center.
Another explanation could be that some layers may slightly shift during the lamination process. Or, the registration may not be 100% dead-center during the imaging process, and so on. These manufacturing issues can result in three different problems.
2.1 Undesired annular ring: If you provide a wide annular ring area, the chances are that the via will be drilled approximately in the middle of the pad. Even though it will not be dead-center, this will still retain good electrical connectivity.
2.2 Tangency: If the PCB designer doesn’t provide a wide enough annular ring area, then the hole could almost end up touching the boundaries of the pad.
This leads to an annular ring width that equals 0. Here, the drilled hole forms a tangent with the outer rim of the annular ring, called tangency. This will lead to connection problems between the via and the copper traces.
2.3 Breakout: When the hole shifts over the copper pad, the drill bit might deviate outside the pad during the drilling process. This is what we call an annular breakout. It can lead to connection problems between the via and the layers. It also causes problems with component placement, solderability, and so on.
Design tips for annular rings: Getting the perfect annular rings predominantly depends on your PCB manufacturer. So, it is always good to find out their capabilities before placing an order. Also, the annular ring depends upon the IPC spec you want to build the boards to, class 2 or class 3.
Signal checks should be done for parameters like conductor width, spacing requirements, controlled impedance, and hole registration.
3.1 Conductor width: This is crucial as it directly impacts the functionality of a PCB. Additionally, increasing signal flow through PCB traces generates an immense amount of heat.
Monitoring conductor width also helps to minimize heat build-up that typically occurs on boards. It also ensures the safe transmission of current without overheating and damaging the board.
Trace width calculation: Many manufacturers opt for their default trace width value available, which may not be suitable for high-frequency applications.
Moreover, depending on the application, the trace width is varied, thus affecting the current-carrying capacity of the conductor. The maximum current carrying capacity for 2 oz copper with a temperature rise of 10°C is mentioned in this table.
Maximum current capacity (amps)Minimum trace width for external layers (mil)Minimum trace width for internal layers (mil) 219..03 466..86 ..34 ..21 ..05IPC- gives the formula for calculating the trace width for allowable current:
Width[mils] = A[mils^2]/(Thickness[oz]*1.378[mils/oz])
As per IPC-, for internal layers, k = 0.024, and for external layers, k = 0.048.
The following formula calculates the cross-sectional area A:
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A[mils^2] = (I[Amps]/(k*(ΔT[deg. C])^ 0.44))^(1/0.725)
Where I is the current, k is a constant, ΔT is the temperature rise, and A is the cross-sectional area of the trace.
During the design phase, you should consider the trace width as one of the most important parameters, as it impacts the performance of the circuit board. This also helps to ensure the safe transmission of current without overheating and damaging the board.
Challenges with conductor width: The maximum current-carrying capacity of a copper trace usually differs from the theoretical value due to several factors. Some of the factors include the number of components, pads, and vias.
Moreover, super large transient surges can lead to the burning down of a trace between pads during the initial supply of power or when modifications are implemented on traces. To avoid such complex issues, we prefer to increase the trace width.
Design tips for conductor width: It is highly preferred to calculate the PCB trace current-carrying capacity to decide the precise trace width. The minimum spacing is done to limit the excess losses. Usually, the traces’ size on an outer layer shouldn’t be below 4 mils, as plating needs to be performed on these traces.
Adhere to the CM’s minimum/maximum line width and spacing capabilities based on the copper weight.
For more details on trace width calculation, check our blog how to optimize your PCB trace using ipc- standard.
3.2 Line spacing: Maintain distance between two traces to avoid flashover or tracking between electrical conductors. Factors such as voltage, application, and type of assembly impact spacing requirements as well.
Line clearance and creepage requirements: Clearance is defined as the minimum distance through the air (medium) between two conductors. Lower clearance among PCB traces can lead to overhead clearance, resulting in overvoltage.
This causes an arc between neighboring conductive traces on the PCB and surface breakdown due to a high-voltage spike. The measurement of clearance depends on factors such as the PCB material, applied voltage, and temperature variations. For more detailed info, read the importance of PCB line spacing for creepage and clearance.
Creepage is defined as the shortest distance between two conductors on a PCB along the surface of the insulation material. Factors such as board material and environmental conditions affect the creepage requirements.
Several measures are implemented to avoid these errors, such as moving tracks and increasing the surface distance in your design. You can avoid spacing errors by adding a slot between traces or placing vertical barriers of insulation.
Design tips for line spacing: Spacing reduction can be achieved by adopting double-sided assembly and implementing insulating materials. Insulating materials act as a sheet barrier for high-voltage nodes. They also cover overexposed high-voltage leads.
Board edge clearances can be influenced by panelization techniques, like V-scoring or mouse bites, especially when using frames or breakaway rails. These mechanical considerations shouldn’t be an afterthought.
This is where a shift-left approach becomes critical, where you involve your PCB supplier early during stack-up and design planning.
3.3 Controlled impedance: To avoid reflections, crosstalk, and timing issues, high-speed PCB designs require controlled impedance. Here’s how to ensure your impedance values stay consistent across the board.
3.4 Hole registration: It is the displacement of the drilled hole from the target. This displacement value determines the accuracy of the hole registration. Misregistration of the hole can lead to a violation of the minimum annular ring requirement, which should be avoided at any cost.
3.5 Missing copper: After generating an IPC netlist out of a schematic, it should be compared with CAM-edited data to identify any missing interconnections. As this can result in missing copper.
3.6 Stubs (unconnected lines): This may occur due to a high level of complexity in a PCB design. It is always difficult to locate unconnected lines. They can result in a hairline short defect that occurs during PCB manufacturing processes. You can correct such errors by allowing a larger clearance between copper connections and pads.
Consider these DFM guidelines for error-free solder mask and silkscreen:
Ideally speaking, the function of the solder mask is to cover all traces, i.e., to isolate solderable and non-solderable areas. But practically, there exists a tolerance that decides how close the solder mask can be to surface elements.
Therefore, the clearances in densely-packaged designs cannot be increased arbitrarily. Generally, the all-over clearance should be half the conductor spacing width. There can be instances where it is not advisable or not even possible to apply a solder mask.
For example, places where heat sinks are used, where the separation between pads is very small, and when a component is too close to drilling holes.
These areas where the solder mask is not applied are usually defined by solder mask clearance restrictions. It avoids the formation of solder bridges.
Design tips for solder mask clearance
To learn about prevalent solder resist defects, see 6 common solder mask errors every PCB designer should know.
Silkscreen helps identify components and their orientations, various test points, marks, etc. It is the responsibility of every manufacturer to employ silkscreen guidelines as part of their DFM checklist.
Silkscreen considerations during circuit design
In today’s digital workflow, most engineers review assembly files on a screen, not large-format prints. That means your silkscreen text doesn’t need to be oversized for print readability. As long as it’s legible in a zoomed view on a PDF or CAD viewer, you’re good to go. This shift allows for more efficient use of board space without sacrificing clarity.
Choosing the right design tool is essential. In good DFM practices, we should consider functioning, cost, and quality along with the desired output before the manufacturing process starts.
These design tools combine design tactics and manufacturing processes to realize the precise manufacturability level in the design. The best DFM tool should be able to provide detailed information about how the design choices will impact the outcome/manufacturability of the circuit layout.
Always discuss with your manufacturer if you have not been formally trained or have not used it very much. Before selecting the DFM tool, consider the following aspects:
DFM issues cannot be avoided completely, but can be detected in the early design stages. The process is expensive, but nowadays, we have several tools that provide the same in-depth analysis at a low cost.
It can be easily used and deployed in the PCB layout process. Design for testing that involves a thorough examination of the board’s electrical conductivity is also a vital aspect of fabricating a flawless board.
A good DFM process ensures that the layout is not only optimized for electrical performance but can also be manufactured easily on a large production scale without increasing cost, risk, and time factors.
To produce quality circuit boards, you should know the latest DFM rules to avoid problems during the initial manufacturing stages.
Key takeaways:
Requirements for high-density interconnects, high currents, better performance, advanced processes, and special materials have made design for manufacturability a critical step. If you have any questions regarding the DFM of your board design, please share your comments below. Our engineering team will be happy to help you out!
Have questions on your PCB design? Post them on our forum, SierraConnect. Our design experts will answer them.
Your time is valuable, which is why you want to design your printed circuit board correctly from the start. In our comprehensive guide, we cover everything you need to know, including PCB design basics and steps, materials and composition, best practices, and more so that you’re prepared to design the best possible printed circuit board.
PCB Design Basics
Step by Step PCB Design Guide
PCB Design Best Practices
PCB Composition & Materials
PCB Layout Capabilities
A printed circuit board (PCB) is a flat plate or base of insulating materials that contains a pattern of conducting material and components, and some projects can be quite complex. But all PCBs have to start somewhere — and that’s with design.
Why are PCB design basics so important? Multiple extensive revisions can seriously delay the completion of your project — costing you time and money. It’s important to work with engineering experts from the beginning so that you can design for manufacturability and ensure a final, cost-effective product that works efficiently and effectively.
From the initial drawings to the final files, here are the 9 steps toward designing a printed circuit board:
1. Understand the electrical parameters.
Before starting a PCB design, you should know and understand the electrical parameters of the system, including:
2. Creating the schematic.
One of the first steps is always creating a schematic, which refers to the design at the electrical level of the board’s purpose and function. At this point, it’s not yet a mechanical representation.
3. Use a schematic capture tool to create your PCB layout.
The right PCB provider will work with principal engineers to develop a schematic with a software platform such as Mentor PADS®, Allegro, or Altium, which shows you exactly how your board will operate and where the components will be placed. After you create your schematic, the mechanical engineer will load the design and determine how it will fit in the intended device.
4. Design your PCB stackup.
This is important to consider early on in the PCB design stage due to impedance, which refers to how much and how quickly electricity can travel down a trace. The stackup plays a role in how the mechanical engineer can design and fit the PCB into the device.
5. Define design rules and requirements.
This step is largely dictated by standards and acceptability criteria from the IPC, which is the industry association for PCB and electronics manufacturing. These standards tell you everything you need to know regarding PCB manufacturing. An important tip: Find a PCB layout provider who is extremely familiar with IPC standards; this can help you avoid major revisions and project delays.
6. Place your components.
In many cases, the customer and PCB provider will discuss design and layout guidelines when it comes to the placement of components. For example, there may be standards indicating that certain components cannot be placed near others because they create electrical noise in the circuit. The PCB provider will have data sheets on every component (in most cases these are connectors), which will then be placed in the mechanical layout and sent to the customer for approval.
7. Insert drill holes.
This step is driven by the components and a connection. About half of the flex circuits on the market are double-sided, which means they have connection to the drill hole on the bottom layer.
8. Route the traces.
After you’ve placed the components and drill holes, you’re ready to route the traces, which means connecting segments of the path.
9. Add labels and identifiers.
Now is the time to add any labels, identifiers, markings, or reference designators to the layout. Reference designators are helpful in showing where specific components will go on the board.
10. Generate design/layout files.
This is the final step in the layout process. These files contain all the information pertaining to your printed circuit board, and once they have been generated, your PCB is now ready for fabrication and manufacturing and assembly.
It’s important to communicate with the PCB or flex application engineer during the beginning of any PCB design job and discuss everything you need or require for your project. Open and constant communication with your PCB provider ensures that you’re both on the same page, which can reduce the need for multiple extensive revisions.
While it is rare that a printed circuit board is 100% perfectly designed on the first try, communication will help ensure that your PCB is properly designed from the start and that any revisions are not major ones that will derail your project and timeline.
When you submit a design, you also need to have the right board size, trace width, materials, component placement, and tolerances. Plus, in the case of flex, you’ll need to determine whether the design is static, partly flexible, or dynamic.
It’s also important to consider the environment in which the product has to function. Is the printed circuit board or flex circuit designed for a non-extreme environment, such as your cell , or the highest of extremes, such as an explosion?
You’ll likely have questions about the PCB design and layout process, which means it’s best to find a reputable PCB provider with extensive engineering experience who can answer your questions and ensure a smooth project from start to finish.
A copper-clad substrate or polyimide-based film is often used for flex circuits, and FR4 (or an FR4 stiffener) is used for rigid-flex. FR4 allows you to build up the layers as the technology content is created.
A solder mask is also used, which is a technique where everything on the circuit board is coated with an epoxy-based LPI or cover coat for flex, except the contacts to be soldered, the gold-plated terminals of any card-edge connectors, and fiducial marks.
PCBs also include a legend application, which are the decals and reference designators in epoxy ink on a board. The name refers to the method of application in which the ink is automatically applied similar to ink jet printers
Cirexx can configure digital, analog, mixed signal technology, controlled impedance, matched length pairs DDR, RF layout, and high speed signals up to 100+ GHz for all of the following PCB structures:
For more information, please visit one stop pcb desing service.
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