What Goes Into a PCB Layout Time Estimation?By ZM Peterson • May 15, 2021
If you’re planning a new project and you’re shopping design firms, you’re likely to receive a range of rates and hourly estimates for your project. Not all PCB layout time estimates and costs are created equal and it’s important to know the level of service you’ll receive once your project begins. Some firms are fly-by-night operations that just do layout and nothing else. Others provide full-service documentation, DFM checks, fabrication assistance, schematic and BOM cleanup, and much more.
If you’ve ever wondered how some design firms arrive at their estimates, there is much more involved than the hourly rates paid to the layout team. In this article, we’ll look at some of the factors used to determine PCB design and layout time, as well as the overall project estimate. If you work with a full-service design firm, you can expect to pay a higher overall cost, but much of the administrative and project management burden will be taken off your plate.
Factors Affecting a PCB Layout Time Estimation
Inexperienced designers that only work with simpler double-layer or low-layer-count boards probably don’t realize the host of other tasks involved in ensuring project success. In addition, with dense high-speed digital boards or advanced RF PCB layouts, there are many factors that are needed to ensure successful layout that are sometimes not considered. Lack of knowledge in these areas by some designers leads to project overruns, and sometimes to abandonment by the contracted designer.
While we can’t speak to the specific practices at every design firm, we can tell you some of the general factors that affect a PCB layout time estimation and project cost:
- Part count to net count ratio. Part count and net count together can be used a good starting point for working up a PCB layout time estimation.
- Highest pin-count and smallest pitch BGA. These particular components require careful stackup planning and a fanout strategy to ensure proper layout and routing.
- Layer count: Higher layer counts for a given component count can make layout easier due to simpler routing, although this depends on plane and copper pour requirements.
- Specific digital interfaces: Certain digital interfaces need to have some specific design rules enforced to ensure performance metrics are met. Two interfaces we approach carefully are DDR and PCIe interfaces.
- Unique RF structures: Some RF structures like antennas, bandgap structures, unique waveguides, and passive circuits require very careful design and layout, and these might carry additional requirements beyond the typical rules-defined digital trace.
- Available footprints: Do you already have a complete CAD library for your components, or do these need to be created from scratch? Not all PCB components include footprint data, and these will need to be assigned or created when working the layout.
If you need engineering design services alongside layout services, that can be an entirely separate quote. A good ballpark estimate is to simply take the PCB layout time estimation and double it to determine the total engineering cost. In addition to schematic design and PCB layout/routing, other important tasks include documentation generation, preparation for fab/assembly, and simulation. These are more than just add-on services, they’re imperative for ensuring your design can be successfully produced with high yield and quality.
PCB Documentation Packages
Not all firms require documentation beyond just ECOs or changelogs. Some of our clients require a complete deliverables package that includes mechanical drawings, fab files, and specific documentation, all in very specific file formats. Some projects or clients may require this, and as a prospective client, you should make this clear when requesting quotes. In my experience, some clients prefer to do this portion on their own, probably because they’ve had a bad experience with previous contractors or they’ve received poor documentation in the past.
When searching for a PCB service bureau for your next project, be sure to provide an example documentation package under NDA so that an accurate documentation cost can be included in the quote. If you’re unsure of what documentation you’ll need, an experienced design firm can help you determine if anything is needed beyond the standard set of deliverables needed for fab and assembly.
Example PCB documentation files include fabrication and assembly drawings. Portions of these can be generated in PCB layout software.
Beyond Layout: Simulation, and Manufacturing Management
Not all circuit boards will need to be evaluated with simulations. Board evaluation with simulations can sometimes be an open-ended agreement, depending on the simulation tasks involved. Many of the standard tasks can be implemented in some advanced design tools. These include some important points involved in some high-speed PCBs, high-frequency PCBs, and mixed-signal PCBs, namely impedance/S-parameter verification, impulse response or eye diagram calculations, coupling simulations, and PDN impedance calculations. If something more specific beyond these basic calculations is needed, a full study with a field solver may be required, and it’s generally better to treat this as its own engagement.
Manufacturing management is another area where some design firms are not always transparent. Some design firms will claim to offer PCB prototyping services and will quote a premium for it as part of the project cost. What they are really doing is outsourcing your design to an overseas manufacturer for bottom dollar, and they will charge a 50% to 100% markup. They generally will not perform any of the important DFM checks, BOM sanitation, or manufacturing management tasks required to make sure you receive your boards on time, on budget, and with required quality.
Be careful when contracting with a PCB design firm for outsourced PCB manufacturing services.
Testing and Qualification
Testing is another important service that is needed to validate finished prototypes. Some projects might require the design team to perform some basic functional tests or board bring-up tests to ensure the board is ready for deployment. This is typical when your design firm is also developing basic firmware as they will probably be the best party to ensure everything is working as designed. The designers are probably also the best team to suggest modifications in the next revision after testing is completed. For high-volume projects, the manufacturer will need to perform some basic tests, and the designer will need to specify test requirements for automated PCBA testing.
Another problem is with conformance to industry qualifications and design standards. Other PCB layout firms and their low-budget manufacturers almost always cannot guarantee any qualification to IPC Producibility Levels, IPC Performance Classes, FCC/CISPR/UL/IEC standards, or other IPC standards. This places you at significant risk of a scrapped design once you receive your boards in the event you plan to scale production and go to market.
Don’t take chances with your next PCB layout time estimation with a low-budget, inexperienced design firm. NWES provides full-service PCB layout and manufacturing management services to innovative companies in multiple industries and verticals, including aerospace OEMs, and defense primes. Our managed manufacturing services come with a fixed fee rather than a large markup, and we’ve partnered directly with EDA companies and advanced ITAR-compliant PCB manufacturers to help ensure your next design is fully manufacturable at scale. Contact NWES for a consultation.