Common Printed Circuit Board Design Rule Violations

Printed circuit board design can be very challenging, even for the most experienced design engineers. There are many reasons a printed circuit board design can be held up in production for design rule violations, but AdvancedPCB makes it easy to find out if your design files contain possible manufacturability issues. FreeDFM is a free online tool that was developed by AdvancedPCB to quickly identity manufacturability issues in your printed circuit board design files. We recommend that after you have exported your circuit board design files in Gerber format, compress them in a .Zip folder and upload them to FreeDFM for a quick check.

The FreeDFM check only takes a few minutes and you will receive a detailed report outlining any issues found. Knowing about the issues in your circuit board design will save you money and time, but the software will also send a discount code for up to $100 off your next PCB order. So, what’s the catch? Why would AdvancedPCB create a free tool and basically pay you to use it? The powerful tool actually saves AdvancedPCB time and makes the front-end planning and CAM for your PCB fabrication job a smoother process.

Below we list some of the most common printed circuit board design rule violations.  Keep an eye out for these in your next printed circuit board design; but don’t worry, AdvancedPCB’s large team of experienced CAM engineers inspect each and every customer’s file prior to production and will quickly notify you if there is a manufacturability issue with your printed circuit board design.

Improper Annular Ring

An annular ring is the portion of conductive material completely surrounding a hole. A minimum of .005″ annular ring for vias or a minimum of .007″ for component holes is required for manufacturing your printed circuit board design. AdvancedPCB requires that vias with connecting traces have a pad that is 10 mils larger than their drill, and component through holes with electrical connections have a pad that is 14 mils larger than their drill. Tooling holes with no electrical connections may have 0 mil annular ring.

Insufficient Copper Trace Width/Spacing

Copper “Spacing” in your printed circuit board design refers to the air gap between any two adjacent copper features. “Trace width” is the width of a copper feature (usually traces) and the proper width for printed circuit board conductors for a given current can be calculated using our online Trace Width Calculator, which uses formulas from IPC-2221. AdvancedPCB requirements call for the following:

• For 1 oz: finished copper weight (inner layers), the minimum trace width/space is 0.005″.
• For 2 oz: finished copper weight (inner & outer), the minimum trace width/space is 0.006″
• For 3 oz: finished copper weight (inner & outer), the minimum trace width/space is 0.010″
• For 4 oz: finished copper weight (inner & outer), the minimum trace width/space is 0.012″
• A premium is charged for trace width/spacing less than .007″. (We can process .004″ for 1 oz. CU. finished (outer layers) and .5 oz. CU finished (inner layers).

Exposed Copper

Exposed copper on the printed circuit board’s edge or visible on the inside of cut-outs and on the inside of non-plated drill holes are problematic. For single boards, Tab-Routed Arrayed boards and boards with Cut-outs, follow these requirements: Outer layer copper should be at least 10 mils away from the center of the board edge to prevent exposed copper. Copper within 10 mils of the center of the rout line may be exposed and viewable from the board edge. Inner layer copper should be at least 10 mils away from the center of the board edge to prevent exposed copper.

Drill Holes Too Small or Too Close

Drill hits that are small and too close to other small drill hits can be a show-stopper. AdvancedPCB requires a minimum of 10 mil spacing (edge to edge) between drilled holes that have a diameter less than 65 mils. Otherwise drill bits can break during high speed drilling.

For more information about AdvancedPCB’s CAM procedures and ways to avoid production holds, give us a call at 1-800-979-4722, or contact your AdvancedPCB Representative directly.