Resist Sliver (Acid Trap) Detection
A common problem caused by 90-degree bends during auto-routing is Resist Slivers (sometimes referred to as “Acid Traps,” depending on your fabrication process). These slivers of resist material, when too small, will typically flake off the PCB during fabrication and re-deposit themselves elsewhere on the board. The results can cause both opens and shorts. Since this is a totally random situation, troubleshooting is difficult and time consuming. You will benefit by being able to find potential Resist Sliver problems prior to fabrication. Once located, the Resist Sliver can be corrected either by re-routing the traces involved, or by using the GerbTool’s AutoCorrect feature to fill in the offending area.

Copper Sliver Detection
Copper Slivers can be found on a variety of layer types; they are most commonly associated with internal “negative” plane layers that are using a “paint/scratch” technique for embedding traces within that layer. Additional instances can also be found on “positive” trace layers, particularly when “hatch” fills are used for ground shielding. The small areas of copper (slivers) that sometimes result in these situations have minimal surface adhering and can thus flake of during the etch process (similar to that of a Resist Sliver). While most of the Copper Slivers will dissolve on the etch tank, some will re-deposit and cause random shorts. You again benefit by being able to locate potential trouble spots prior to fabrication, and then eliminate the offending sliver either manually or via the AutoCorrect feature.

Solder Mask Sliver Detection
Yet another form of slivers, these pertain to solder mask data. Solder Mask Slivers are most commonly found on fine-pitch, surface-mounted devices where the webbing between pads is less that 5 mils wide. Even with Liquid Photo Imageable (LPI) solder mask technology, fabricators still have issues with producing areas of solder mask this size. Typically fabricators prefer the most solder mask coverage possible, but with the largest opening possible without exposing adjacent data. They will benefit by using this feature to balance between the largest opening possible while helping to insure that an abnormally high number of slivers do not result in the process. Should slivers occur, conductive pads could become contaminated, thus creating scrap boards just like a short or open issue could. Another problem here is that, if not found early, this issue will likely not appear until the boards are fabricated and out for assembly. Once the boards have components on them, the cost of scrap increases incrementally.

Solder Bridge Detection
Designed to work hand-in-hand with Soldermask Sliver Detection, Solder Bridge detection allows you to locate situations were the soldermask openings are too large. When a mask opening is too large, it will typically expose adjacent conductive objects, which can result in shorts during the pre-tin or assembly phase of manufacturing. Once again the benefit here is to let you balance between maximum soldermask coverage while maintaining the largest possible opening for ease in fabrication.

Pin Hole Detection
Similar to Copper Slivers in physical shape, Pin Holes are actually the reverse. Commonly found in both solid- and hatched-filled areas, Pin Holes are small pockets or voids within a given copper area. These voids typically will not fabricate well for two reasons: A.) either the Resist flakes off or B.) The void over-etches and becomes larger than normal, thus leaving small pockmarks in the offending copper area. These Pin Holes are a big issue within hatch-filled ground shields where hatch lines are spaced around a border such that they do not touch or close that area. You benefit by quickly being able to scan any conductive layer and locate potential Pin Holes, which in turn helps to avoid costly scrap boards on a given job run. Additionally, you can make quick corrections to these problems by applying the AutoCorrect feature found within GerbTool – Pin Holes will be filled and sealed for a small, clean copper fill.

Starved Thermal Detection
Starved Thermals are one of the biggest issues with Designers, as most of the CAD system DRC functions do not look to see if a thermal has been choked off or restricted by adjacent data. This is because most CAD systems do not provide a “true” representation of the thermal aperture. GerbTool represents the thermal aperture shape that will be used during fabrication, and you benefit by using this feature to validate the thermal connections and their relationship to adjacent clearances and thermals. If there is an adjacent object too close to a given thermal, it will starve or restrict the connection of that thermal to a given plane layer. In some cases, restrictions are so severe that the thermal loses connection all together.

Isolated Thermal Detection (Unique to GerbTool)
Similar to Starved Thermals, and a bigger problem with Designers, Isolated Thermals are those that have become cutoff from a given plane layer due to objects that are not directly adjacent to the thermal. Situations like this are commonly found in large, multi-pin connector headers where a thermal is buried in the middle of the connector and the clearances throughout the rest of the header pins are too large -- which results in the thermal being cutoff. GerbTool provides you with an automated mechanism for searching around a thermal for these conditions. In addition, you can even play “what-if” scenarios and apply a fictitious “over-etch” amount to increase the effectiveness of this feature.

Soldermask-to-Trace Spacing (Unique to GerbTool)
Solder Mask-to-Trace Spacing is another feature that allows you to look for “what-if” conditions. Even LPI soldermasks have a certain amount of “float” when applied to a job. Usually this float is very minute -- in the 1-3mil range -- but if you have a mask opening whose edge is only 2 mils off the edge of a conductive object, you could end up with a random solder bridge condition at that location. Allowing you to look for potential “what-if” conditions provides the added security of knowing that your job will be as easy as possible for the fabricator to manufacture, which in turn allows the Designer to benefit from increased time-to-market and fewer scrap boards.

Layer-to-Layer Registration
More of a sanity check than a full out fabrication check, the Layer-to-Layer registration feature lets you find situations where multi-layer jobs no longer stack-up properly. This is a very common problem within CAD tools, like the PowerPCB product, that try to be too smart for their own good and register a layer’s data based upon its physical extents inside a given film size as opposed to sticking with a fixed origin location. While this feature is an option for most systems (PowerPCB included), many users never go in and change the defaults, and simply try to live with misaligned layers. While gross misalignments are pretty obvious, it is those jobs that have the ever-so-slight alignment problems that are the issue. Left untouched, the Designer could end up getting boards back with weakened annular rings on pads, or complete break-out conditions. Either way, the boards are scrap, as even a weakened annual ring is no good – especially in high-current conditions where the annulus can become a fuse, depending on the weakened location. GerbTool users benefit by identifying this situation up-front and rectifying it before the data leaves their hands.

SMD-to-SMD Spacing & Pitch
Equally useful as both a validation check and an information check. SMD-to-SMD Spacing & Pitch lets you look for potential problem areas quickly and efficiently. This check is typically made during pre-analysis quoting scans. By checking the edge spacing and pitch of SMD pads, you can tell whether additional situations might exist, like soldermask and resist slivers.

Enhanced Solder Mask Annular Ring Checking
While this check already exists, you will benefit from the additional enhancement of reporting back negative numbers when a mask clearance actually covers a conductive pad. Most other CAM tools simply report a “zero” clearance; however what you really want to know is how much the clearance encroaches upon the pad, because in certain types of high-density manufacturing it is actually desirable to have the soldermask on top of the edge of pads as it helps to keep the pad planted on the circuit board material. This technique is sometimes referred to as “solder mask capping.”

Minimum Trace Width, with Board Average (Unique to GerbTool)
Used for information and checking purposes, Minimum Trace Width analysis allows you to get a feel for what type of line width will have to be fabricated on a given job. This can ultimately affect the costing of a job, as well as the technique that might be used to perform the fabrication itself. This feature allows Designers and Fabricators alike to benefit from previewing the characteristics of a job before it has been fully tooled.

Minimum Air Gap, with Board Average (Unique to GerbTool)
Like Trace Width checking, Minimum Air Gap also works equally well as an information and validation feature. It provides you with insight as to the density requirements of a given job prior to tooling. This information will again impact both the costing and fabrication technique of a layout, and is typically used during quoting or pre-tooling scans.

Silkscreen-on-Pad Detection
While features already exist to fix Solder Masks-on-Pads. the operator doesn’t know to run the function unless there is something during the pre-tooling analysis that tells them this condition exists. None of the PC-based CAM tools do this today -- only the high-end tools from Valor and Barco offer this type of check. Now GerbTool users benefit from the same pre-tooling analysis capabilities found within the higher-end products, which in turn helps to streamline and improve their overall CAM flow.

Net Open
Net opens are conditions where two or more GerbTool nets are sharing the same coordinates as a single external net. This condition is typically caused by a missing trace or thermal connection. GerbTool will highlight the external net while simultaneously highlighting the internal GerbTool nets, each with their own unique color. You can quickly isolate the situation through GerbTool’s unique method of visualizing the problems.

Net Short
Net Shorts are the opposite of net opens; here two or more external nets are sharing the same coordinates as a single internal net. This condition can be caused by a myriad of things; the more common situation is an extra trace that improperly ties two nets together, or perhaps a thermal connection that is in the wrong location. For this situation GerbTool will highlight the internal GerbTool net while simultaneously highlighting the external nets points in their own unique color (one color per net). This method of visualization allows you to quickly track down where the board has been misrouted.

No Copper
No Copper errors indicate that there is an external net but not corresponding copper at that location. This is typically caused by a missing pad at a particular location.

No External Net
No External Net errors are the opposite of No Copper: here there are nets present within the GerbTool design, but there are no corresponding external nets to validate against. These errors could occur because someone may have added additional circuitry to a design after the original netlist was generated, or the external netlist may only have end-points of nets contained within it.