PCB plotting refers to the process of creating a physical layout or design from a conceptual electronic design as part of the PCB manufacturing process. This is a critical step where the digital blueprint becomes the guide for the actual board that will be produced. Here’s a deeper dive into what PCB plotting involves and why it’s important.

Understanding PCB Plotting

•From Schematic to Design: Before plotting begins, the PCB design is conceptualized in a schematic. Engineers then use electronic design automation (EDA) software to translate these schematics into a digital model of the PCB, including all layers, copper traces, vias, and components. This digital model is what will be 'plotted' onto the physical board.

•Gerber Files: The industry-standard format for PCB design files is "Gerber" format. These files contain all the necessary information for the PCB's layers and are used by the manufacturing machines. Each layer (copper, solder mask, silkscreen, etc.) will have its own file, and these files act as the 'maps' for plotting the PCB design onto the physical layers.

•Plotting Process: The term "plotting" comes from older processes where a plotter (a large, specialized printer) was used to create a highly accurate, to-scale print of each PCB layer on a transparent sheet. These sheets (photo masks) were then used in the photo-lithographic PCB manufacturing process, where they helped transfer the design onto the copper layers. Although technology has evolved, the term persists and now refers more generally to the generation of manufacturing instructions/guidelines from digital designs.

•Modern Photoplotting: Today, the process is more direct. Advanced machines use the information in the Gerber files to directly image the PCB design onto the board layers, often using lasers that are far more accurate than older physical plotters. This allows for the incredibly precise transfer of even the most complex and miniaturized designs onto a physical substrate.

•Inspection and Quality Control: After plotting, the PCBs go through rigorous inspection. Automated Optical Inspection (AOI) is a key part of quality control, ensuring that the layout has been accurately rendered onto the PCB and that there are no defects, like short circuits or missing components, which could cause failures.

Importance of Accurate PCB Plotting

•Fidelity to Design: The plotting process must be extremely accurate to ensure the final PCB precisely matches the original digital design. Mistakes in plotting can lead to short circuits, breaks, or non-functional boards, especially in complex, multi-layer PCBs.

•Reliability and Functionality: Accurate plotting is crucial for the reliability of the PCBs, especially for those used in critical applications like medical devices, aerospace, and automotive systems, where a malfunction could be catastrophic.

•Cost Efficiency: Errors in the plotting process can result in the need for redesigns or re-manufacturing, both of which lead to additional costs and delays. Accurate plotting helps in reducing wastage and improving production efficiency.

In conclusion, PCB plotting is a technical and precise process that plays a critical role in electronics manufacturing. With advancements in technology, especially in direct laser imaging and other forms of photoplotting, this process has become faster and more accurate, catering to the needs of modern electronics that often require incredibly detailed and reliable PCBs.

To plot your PCB click the Tools→Manufacturing→ button.

Plot Preview

The plot preview shown above consists of a ribbon menu, a options panel on the left and a preview window to the right of the options panel and below the ribbon menu.

click to print the selected pages.

Ribbon Menu

The ribbon menu can be split into 2 parts, the View button group on the left and the common ribbon button groups on the right.

The button shows/hides the option panel shown below.

Click to read about the Common Print Menu

The Option Panel

Options Dialog

The options panel lets you scale the printing or have the sheets automatically fill the printed page.

Shows this help page.

Scale

The plot scale. Disabled of Auto-fit is checked.

Check to have the sheets automatically fill the printed page, If you uncheck it, you can set the print scale. Note, it is possible to set the scale such that the sheet will not all fit on the printed page.

Scaled (1:1)

Auto-fit

Labels

Check to print plot layer labels

Check to add a the file name to each plot.

Check to add a date to each plot.

Show

Check add small drill target/centers to each pad/via that has a hole. Set pilot holes below.

 The diameter of the drill pilot hole.

Check to add targets to  the printed output.

Check to include the PCB border in the printed output.

Include the full shape of the holes in the plots. Holes will only appear in copper areas: they will not appear in areas with no copper. You are not advised to add holes as this will lead to drill hole miss-registration.

Drill miss-registration

Drill miss-registration (3D)

The color of the 'dark' material in the plot.

Layers to Plot

Plot

Check/uncheck the check boxes in the Plot column to include/exclude the layer in the print run.

Negative

Check/uncheck the check boxes in the Negative column to print that sheet in negative.

Reverse

Check/uncheck the check boxes in the Reverse column to print that sheet reversed in the horizontal direction.

Restrict

If plotting negative the fill color restricted to the PCB border.

Clicking displays this help topic.

No Hole or Pilot Hole (Negative)	Holes (Negative)
Drill Pilot Hole (Negative)	Hole and Drill Pilot Hole (Negative)
No Hole or Pilot Hole (Positive)	Holes (Positive)
Drill Pilot Hole (Positive)	Hole and Drill Pilot Hole (Positive)

Drill Snatch and Pilot Holes

Drilling pilot holes can help prevent "drill snatch," especially in harder or more brittle materials. Here’s how this works and why it's helpful:

•Pilot Holes Reduce Drill Snatch: A pilot hole is a small guide hole drilled before using a larger drill bit to reach the final size. By removing a small amount of material first, the larger drill bit encounters less resistance, which helps it cut more smoothly into the material. This reduces the chance of the drill bit catching or snagging, which can cause a sudden jolt or "snatch."

•Why Drill Snatch Happens: Drill snatch can occur when a drill bit is forced into the material, catches on a hard spot, or enters the material unevenly, causing the drill to jerk. This is common in materials like wood, metal, and printed circuit boards (PCBs), where drill bits can easily bind if they aren't guided properly.

Benefits of Pilot Holes:

•Controlled Entry: Pilot holes help align the larger drill bit, ensuring that it enters the material evenly and smoothly.

•Reduced Strain on Tools: With pilot holes, drills and drill bits encounter less resistance, which helps reduce strain on the tool and bit.

•Cleaner, More Accurate Holes: Pilot holes help produce cleaner holes, preventing cracking, chipping, and potential misalignment.

When working with delicate materials, such as PCBs, starting with a pilot hole is particularly effective in minimizing drill snatch and achieving a professional finish.

Creating a Rectangular Array

You can create a rectangular array by setting Rows or Columns to more then one.

The number of vertical rows.

The number of horizontal columns.

The spacing between each PCB board.

Creating a Rectangular Array