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Tips & Tricks for PCB Production

https://blog.screamingcircuits.com/2019/04/pcb-design-tip-of-the-day.html

There’s so much to think about while working on a new project -- from client requirements to code to incorporating the latest and greatest components -- that engineers sometimes neglect a critical part of electronics: their PCB layout. Poor PCB layouts, incorrect netlists, and unclear mechanical drawings can cause function and reliability problems in your finished piece, as well as production delays.

You can speed up your PCB project by checking for these common issue before submission. Doing so will not only prevent delays, but ensure your piece works correctly and reliably!

Check Your Netlist for Errors

While working on a complex schematic, it’s easy to make a mistake or leave something out. As such, broken netlists are a very common issue we encounter. Usually the errors are small, but sometimes we run into glaring issues with a customer’s file. In fact, recently a customer submitted a netlist without any pin numbers!

A simple way to check for errors before you submit your netlist to us is to export it -- if you receive a syntax or other error message from your program, then you know you’ve got a problem. If you’re lucky, the error message will be specific enough to tell you where the issues are located. In addition to exporting, most schematic capture programs come with at least on verification utility you can use to look for issues. Taking these quick steps will help ensure your netlist is correct and ready for production.

Look for Single Node Nets

If you are working from a multi-page schematic, be sure to double check off-page connectors to ensure they are named consistently (and connected correctly). It may be that a different engineer had been working on the schematic previously and used a different name, or the connectors were given similar, but not correct, names.

If one of the connector is keyed in incorrectly, the result will be a one-component pin seemingly connected to itself. Most schematic programs have automated checks that look for these single node nets and help you resolve naming issues.

Use Consistent Abbreviations

If you have copied pages from other schematics and place them in your current project, or working with a team of engineers, it’s essential that you take a few minutes to look things over to confirm you have used the consistent abbreviations. Common aspects like ground and power are big culprits here. Often we see “grd” on one page followed by “gnd1” on another. This inconsistency results in major errors, and is even more common with power nets -- with +5v on one page, +5 on another. Correct abbreviations are one of the first things we look at when we begin a project.

Ensure Connector Locations & Orientations are Correct

We recently received a board containing a large d-sub connector with over 70 pins. Our team spent several hours connecting signals and resistors to it, only to find out the client had intended the connector to go on the back side of the board. The lesson here is to clearly mark the locations and orientation of any connector on your mechanical drawings - what is clear to you is not to us!

Clearly Define Your “Keep Out” Zones

Similar to the connector issue, it’s vital that you clearly define any “keep out” zones intended for aspects such as mounting holes or sensitive circuitry. While you are defining those zones, remember that solder mask isn’t considered a reliable insulator, so take care that there is proper distance between copper and any mounting hardware. Failing to properly design and define your keep out zones will lead to major issues such as creating a shock hazard on your board, causing electromagnetic interference, or winding up with an unmountable part