Most PCB layout software will display your PCB design perfectly on the screen, and pass it thru their Design Rules Check (DRC) with 'flying colors'. At this point you should be confident enough to generate Gerber/NC files and send them out for fabrication... Right? Unfortunately Wrong... There are two common mistakes which may cause your boards to fail and become very costly to your wallet and reputation: |
1. Don't Automatically Trust the Gerber files generated by your PCB Layout Software.PCB layout software has always had a history of not being able to output "100% reliable" Gerber files (plane layers especially). Why is there a problem outputting reliable Gerber files? The Gerber Format is just unintelligent X,Y coordinate data with apertures (that's right apertures which were used in early plotters back in the 70's). To output Gerber files, your PCB layout software must dismantle and break apart its' own intelligent design database - down to simple X,Y coordinates and apertures. Generating Gerber files for plane layers (power/ground) and mixed technology are the most prone to hidden problems and mistakes. What about ODB++ and IPC-2581, will these new formats eliminate the problem? Unfortunately no, the same problem still exists when outputting to other manufacturing formats such as ODB++, IPC-2581, etc. These formats are more advanced but still built upon a foundation which uses X,Y coordinates with shapes (i.e Apertures). The same mistakes that appear in Gerber commonly appear in these newer formats. Important: It really doesn't matter what your PCB layout software displays on the screen or the results from their DRC checks... it's the outputted gerber files which determine the final quality of your boards. Here's a more detailed article about these potential pitfalls: Don't blindly trust your Gerbers |
2. Lack of true Manufacturing Checks (DFM).A PCB layout software's primary focus is to check for design integrity and not necessarily manufacturing integrity. Manufacturing specific issues are much more difficult to detect and can quietly cause your boards to fail or have poor performance. Common manufacturing checks (DFM) include: Acid traps, Copper Slivers, Antennas, Solder Bridging, Starved Thermal, Ground Plane Check, Thermal Conflicts and much more. An Independent Third Party DFM Check is Essential: Avoid using DFM software and PCB Layout software created by the same company. Chances are if their PCB Layout software missed a manufacturing problem, those same mistakes will get overlooked or unnoticed in their DFM software. An independent third party DFM solution is always recommended for the most reliable results. |
Advanced DFM Check Severity Level: |
Critical: The PCB will fail and/or have very low manufacturing yields. |
Elevated Risk: May result in poor PCB performance. |
Common: Cause delays and/or additional problems during PCB fabrication. |
Acid TrapsDue to the surface tension during the etching process, larger deposits of acid may get trapped into certain areas - resulting in over-etching. Critical: Over-etching will directly effect your board yields and performance. |
|
Find Net DiscrepancySearch for overlapping copper objects which have different nets defined. This net discrepancy typically occurs when the PCB layout software has incorrectly outputted intelligent formats such as ODB++ and IPC-2581. Critical: Indicates a potential short originating from the PCB design. May result in poor board performance, failure, or other undesired effects. |
|
Copper SliversNarrow areas in the copper where the potential for over-etching is great. This typically happens when trace angles are 30 degrees (or less), when composites are used, and on plane layers. Critical: A board can fail if certain copper area are over-etched. Resulting in shorts and decrease in board yield. |
|
Antennas / Dangling TracesSearch for Non-terminating traces which may behave as an antenna. Such traces may be intentional, but a warning is reported as a precaution. Elevated Risk: May result in poor board performance, short, or other undesired effect. |
|
Minimum Clearance: Outer LayersMay cause under-etching on copper areas and/or exceed PCB fabricators capabilities. Resulting in possible opens or shorts. Critical: May result in poor board performance, short, or other undesired effect. |
|
Minimum Clearance: Inner LayersMay cause under-etching on copper areas and/or exceed PCB fabricators capabilities. Resulting in possible opens or shorts. Critical: May result in poor board performance, short, or other undesired effect. |
|
Minimum Annular Ring: Drill-PadSearch for all plated drills and ensure they have a minimum copper annular ring. Having a minimum copper annular ring around each drilled hole is required to assure it will be properly fabricated. Critical: In many cases, drilled holes are not perfectly registered within the exact center of each copper pad. Not having enough of a copper annular ring, may make plating on vias, as well as solder-ability on component holes more difficult. In extreme cases, may result in poor board performance, failure, or other undesired effects. |
|
Minimum Clearance: Track-TrackLocate tracks (with different nets) on the same signal layer that are placed too close to each other. Critical: May cause under-etching on copper areas and/or exceed PCB fabricators capabilities. Resulting in poor board performance, short, or other undesired effects. |
|
Minimum Clearance: Track-PadLocate tracks and pads (with different nets) on the same signal layer that are placed too close to each other. Critical: May cause under-etching on copper areas and/or exceed PCB fabricators capabilities. Resulting in possible opens, shorts, or other undesired effects. |
|
Minimum Clearance: Pad-PadA copper pad on the signal layer is placed too close to other copper pads (with a different net). Critical: May cause under-etching on copper areas and/or exceed PCB fabricators capabilities. Resulting in possible opens, shorts, or other undesired effects. |
|
Non-Functional Internal PadsEssentially these are unconnected internal pads typically found on plane layers. Elevated Risk: May break loose and cause potential drilling problems, risk of shorts, and more. |
|
Minimum Pad SizeA very small diameter pad placed on a signal layer. This typically occurs when incorrect pad stacks are defined within the PCB layout software, or an error has occurred when PCB layout software has generated the Gerber data. Elevated Risk: May cause etching or soldering problems during fabrication. Smaller pads also provide less mechanical support for component leads. |
|
Clearance from Board EdgeObjects are placed too close or outside the PCB border. Elevated Risk: May result in exposed copper at the board edge which could lead to corrosion and long term reliability problems. |
|
Minimum Width: SMT PadLocate SMT pads on top/bottom signal layers that have a smaller width than permitted. Elevated Risk: May cause under-etching and/or uneven pad widths. May also result in poor soldering performance & misalignment during assembly. |
|
Minimum Clearance: Rout-CopperSearch for Rout paths that are too close to signal objects. Elevated Risk: During NC routing process, copper may be damaged or result in other undesired effects. |
|
Minimum Clearance: Same NetLocate objects on the same net and signal layer that are too close to each other. Elevated Risk: May cause under - etching on copper areas and / or exceed PCB fabricators capabilities.Resulting in possible opens or shorts. |
|
Hole RegistrationFind drill holes that do no align with copper pads, due to potential rounding errors found in the drill data, or other causes. Elevated Risk: This may make plating on vias, as well as solder-ability on component holes more difficult. In extreme cases, may result in poor board performance, failure, or other undesired effects. |
|
Redundant PadsDuplicate pads are commonly included in the manufacturing data generated from PCB layout software. Common: This duplication may result in bloated file sizes, potential issues during DFM verification, NC drilling, and your wallet. That's correct your wallet. Many PCB fabricators use pad counts and drill counts as a factor when quoting prices to manufacture a PCB. Having excessive pad and/or drill counts could lead to increased manufacturing costs. |
|
Minimum Width: TrackLocate tracks which have a smaller width than the allocated distance. Common: May cause etching problems during fabrication. The smaller the trace width, the lower the yield for the PCB fabricator and the more costly your boards may be. |
Power/Ground ShortDetermine any potential shorts between Power and Ground planes. Critical: A board will fail if there is a short between the power and ground planes. |
|
Starved ThermalCheck whether a thermal connection to the copper plane has been constricted by overlapping or adjacent data that is way too close. Elevated Risk: May result in poor board performance, short, or other undesired effect. |
|
Neg. Plane Thermal ConflictsDetermine if any via or plated hole is connected to more than one negative plane together. Elevated Risk: May result in poor board performance. |
|
Isolated ConnectionsOne of the most common problems is to determine whether your PCB CAD system has properly outputted good plane connections to the copper plane. Critical: A board will fail if any plane connections is not properly connect the copper plane. |
|
Drill RegistrationLocate any plated drill holes that do not center over an existing pad. Most likely the Drill layer has either been generated or imported incorrectly. Elevated Risk: This will lead to problems during PCB fabrication. |
|
Minimum Annular Ring: Drill-PlaneSearch for all plated drills on plane (GND/VDD) layers and ensure they have a minimum copper annular ring. Having a minimum copper annular ring around each drilled hole is required to assure it will be properly fabricated. Critical: In many cases, drilled holes are not perfectly registered within the exact center of each pad. Not having enough of an annular ring, may result in poor board performance, failure, or other undesired effects. |
|
Minimum Clearance: PlaneMay cause under-etching on copper areas and/or exceed PCB fabricators capabilities. Resulting in possible opens or shorts. Critical: May result in poor board performance, short, or other undesired effect. |
|
Minimum Width: PlaneLocate metal areas on the plane which have a smaller width than the allocated distance. This typically occurs when PCB layout software has incorrectly generated complex polygons with holes (i.e. dark/clear areas) for the plane layers in the Gerber data. Elevated Risk: May result in poor board performance, short, or other undesired effect. |
|
Minimum Thermal Air gapThe minimum gap permitted between the edge of a thermal connect pad and copper area. Elevated Risk: May result in poor board performance, short, or other undesired effect. |
|
Minimum Thermal Spoke WidthThe minimum allowable width for a thermal spoke. Elevated Risk: May result in poor board performance, short, or other undesired effect. |
|
Minimum Clearance: Plane to DrillSearch for all plated drills and ensure they have a minimum clearance from the plane. Having a minimum spacing around each drilled hole is required to assure there will be no shorts or other undesired affects. Elevated Risk: In many cases, drilled holes are not perfectly registered within the exact center of each clearance pad. Not having enough of a clearance, may result in poor board performance, failure, or other undesired effects. |
|
Minimum Clearance: Plane to RoutSearch for Rout paths that are too close to plane objects. Elevated Risk: During NC routing process, copper may be damaged or result in other undesired effects. |
Minimum Clearance: Silk Screen to Board EdgeThe minimum clearance allowed from Silkscreen to board edge. Any silkscreen objects outside the board edge will also be flagged. Elevated Risk: This will lead to problems during PCB fabrication. |
|
Minimum Width: Silkscreen LineCheck for the minimum width for each object on the silkscreen. Common: If the line width is too thin it will not be legible on the fabricated PCB. |
|
Minimum Silkscreen Text HeightDetermine whether the Text height is large enough on the silkscreen layers. Common: If the text height is too small it will not be legible on the fabricated PCB. |
|
Silkscreen over Solder MaskLocate if there are any areas where the silkscreen overlaps with openings in the solder mask layers. Elevated Risk: May cause contamination of the pads and make electrical testing plus SMT soldering more difficult. |
|
Minimum Clearance: Silk Screen to CopperVerify the minimum clearance between silkscreen objects and copper objects (performed on top and bottom signal layers only). Elevated Risk: May cause contamination of the pads and lead to problems during PCB fabrication. |
|
Minimum Clearance: Silk Screen to DrillVerify the minimum clearance between silkscreen objects and drilled holes (both plated and unplated). Common: May cause problems during PCB fabrication. |
|
Minimum Clearance: Silk Screen to RoutVerify the minimum clearance between silkscreen objects and routed paths. Common: May cause problems during PCB fabrication. |
|
Minimum Clearance: Silk Screen (Line to Line)Verify the minimum clearance between silkscreen line objects. Common: May cause problems during PCB fabrication. |
|
Minimum Clearance: Silk Screen (Line to Pad)Verify the minimum clearance between silkscreen line and pad objects. Common: May cause problems during PCB fabrication. |
|
Minimum Clearance: Silk Screen (Pad to Pad)Verify the minimum clearance between silkscreen pad objects. Common: May cause problems during PCB fabrication. |
Mask SliversAreas in the solder mask where the resist is so narrow that it may cause small pieces of the resist to flake off and present soldering problems later. Critical: A board can fail if the resist lifts in an area that needs to be soldered later on. |
|
Solder BridgesTypically when the mask layers, contain openings which are too large, and may expose other adjacent conductive areas. Critical: During fabrication, copper may get too close and form a bridge to other adjacent conductive areas. |
|
Undersized Mask ClearancesUsed to locate mask openings that may cause de-lamination from the PCB substrate. |
|
Missing Mask Clearances
|
|
Minimum Clearance: Solder Mask to RoutCommon: May cause problems during PCB fabrication. |
|
Minimum Clearance: Mask (Draw to Draw)Common: May cause problems during PCB fabrication. |
|
Minimum Clearance: Mask (Draw to Pad)Common: May cause problems during PCB fabrication. |
|
Minimum Clearance: Mask (Pad to Pad)Common: May cause problems during PCB fabrication. |
|
Partial ClearancesCommon: May cause problems during PCB fabrication. |
Drill-Plane Shorts
|
|
Minimum Drill Size
|
|
Double Drill HitsDuplicate drill hits are commonly included in the manufacturing data generated from PCB layout software. Common: This duplication may result in potential issues during DFM verification, blowouts during NC drilling, and your wallet. That's correct your wallet. Many PCB fabricators use drill counts as a factor when quoting prices to manufacture a PCB. Having excessive drill counts could lead to increased manufacturing costs. |
|
Pads without DrillsCommon: May cause problems during PCB fabrication. |
|
Plated Drill without PadsSearch for all plated drills and ensure they have a minimum copper annular ring on all required metal layers. Having a minimum copper annular ring around each drilled hole is required to assure it will be properly fabricated. Elevated Risk: In many cases, drilled holes are not perfectly registered within the exact center of each copper pad. Not having enough of a copper annular ring, may make plating on vias, as well as solder-ability on component holes more difficult. |
|
Touching Drill HitsOccurs when drilled holes are placed too close to other drilled holes on the circuit board. Common: When trying to drill holes that are too close together, it may cause the drill bits to break during the drilling process. This effect is also known as blowouts. |
|
Minimum Clearance: Plated Drills to CopperCommon: May cause problems during PCB fabrication. |
|
Minimum Clearance: Unplated Drills to CopperCommon: May cause problems during PCB fabrication. |
|
Minimum Clearance: Drills to RoutCommon: May cause problems during PCB fabrication. |
|
Minimum Clearance: Rout to RoutCommon: May cause problems during PCB fabrication. |
|
Minimum Drill Hole SpacingCommon: May cause problems during PCB fabrication. |
Minimum Clearance: ComponentVerify spacing between components is greater than the minimum permitted value. The component outline is determined by either (1) the extent of its pins and any geometric objects drawn in silkscreen, or (2) The extents provided when importing an intelligent ODB++ or IPC-2581 file. Critical: Components that are placed too close together may prevent the board from properly being assembled. |
|
Maximum Component HeightCheck each component height and determine if it exceeds the maximum permitted value. Elevated Risk: If a component exceeds the maximum permitted height it may prevent a fully assembled PCB from properly fitting into a designed enclosure. |
|
Component OverlapsVerify components do not intersect. The component outline is determined by either (1) the extent of its pins and any geometric objects drawn in silkscreen, or (2) The extents provided when importing an intelligent ODB++ or IPC-2581 file. Critical: Components that overlap will prevent the board from properly being assembled. |
|
Invalid RefDes
|
|
Invalid Component Rotation
|
|
Footprint to Pad Registration
|
Minimum Width: SMT Stencil PadLocate SMT pads on top/bottom paste layers that have a smaller width than permitted. |
|
Minimum Aspect Ratio: SMT Stencil PadLocate SMT pads on top/bottom paste layers that have a smaller Aspect Ratio than permitted. The Aspect ratio equals the paste pad width divided by the stencil foil thickness. |
|
Minimum Area Ratio: SMT Stencil PadLocate SMT pads on top/bottom paste layers that have a smaller Area Ratio than permitted. The Area ratio equals the paste pad area divided by the paste pad height and stencil foil thickness. |
|
Minimum Volume: SMT Stencil PadLocate SMT pads on top/bottom paste layers that have a smaller paste volume than permitted. The paste volume equals the paste pad area and stencil foil thickness. |
|
SMT Stencil Pad to Pad Registration Locate SMT pads on top/bottom paste layers and verify the align with pads located on top/bottom metal layers. |
Open Net DetectedCheck all test points and verify the same net is found at each defined location. A violation is highlighted if the extracted CAM net (which is generated from the manufacturing data) differs from the external net defined in the IPC Netlist file. Critical: There is a very good chance your manufacturing data (Gerber, NC, ODB++, etc.) differs from your original PCB Design. A serious error has occurred either in your original PCB design or while exporting to your manufacturing data. A thorough review of your design in the highlighted areas is recommended. We also recommend you verify the export settings used while generating your manufacturing data. |
|
Shorted Net DetectedCheck all test points and verify the same net is found at each defined location. A violation is highlighted if the extracted CAM net (which is generated from the manufacturing data) connects with two or more different external nets defined in the IPC Netlist file. Essentially the same CAM net is found at two (or more) different external net locations. Critical: There is a very good chance your manufacturing data (Gerber, NC, ODB++, etc.) differs from your original PCB Design. A serious error has occurred either in your original PCB design or while exporting to your manufacturing data. A thorough review of your design in the highlighted areas is recommended. We also recommend you verify the export settings used while generating your manufacturing data. |
|
Missing CopperSearch each external net location (defined from the IPC Netlist file), and determine if an extracted CAM net (which is generated from the manufacturing data) exists. Elevated Risk: Essentially an external net location was defined, but there was no CAM net found. This may be non-critical (caused by a single point net or CAM object without a net). |
|
External Net MissingAn extracted CAM net (which is generated from the manufacturing data) exists where no external net was defined (from the IPC Netlist file). Elevated Risk: Essentially a CAM net was detected without an external net defined. In many cases, this may not be considered a critical error. |
Minimum Test Point DiameterCommon: May cause problems during PCB fabrication. |
|
Minimum Distance: Test Point Center to CenterCommon: May cause problems during PCB fabrication. |
|
Minimum Clearance: Test Point to Board EdgeCommon: May cause problems during PCB fabrication. |
|
Minimum Clearance: Test Point Pad to PadCommon: May cause problems during PCB fabrication. |
|
Minimum Clearance: Test Point to MaskCommon: May cause problems during PCB fabrication. |
|
Minimum Clearance: Test Point to RoutCommon: May cause problems during PCB fabrication. |
|
Find Test Point without NetCommon: May cause problems during PCB fabrication. |