Gerber files are proven to provide a clear view of the entire PCB design, clearly displaying the overlays and potentially revealing issues that slow down the quoting process or lead to design rework.
The term Gerber file is familiar to the field of PCB design, manufacturing and procurement. But what exactly is a Gerber file? And where did it come from?
Gerber files originated from Joseph Gerber, founder of Gerber Systems, Inc. In order to promote its vector optoelectronic plotters, the company released the "Gerber format: EIA RS-274-D set; Plot Data Format Reference Manual" in 1981. late 1980s, other CAM systems began in the field of PCB manufacturing The late 1980s, other CAM systems began to adopt the "standard Gerber" format in the field of PCB manufacturing. Soon after, Gerber became the industry's practical application of the data format.
As drawing technology continued to evolve and more powerful raster plotters were created, the "Standard Gerber" format was expanded in 1991 to include polygons and other parameters. This improvement also allowed users to create graphics of various sizes and shapes, and to fill them without drawing them; they could be defined using only openings.
In April 1998, Barco acquired Gerber Systems, Inc. In September 1998, Barco introduced the RS-274X format, an extended version of the Gerber format, to consolidate and unify all the sub-versions then in use in the industry for specific plotter models. This new version soon became the actual data format in use.
Over the years, the 274X format has undergone several revisions that have enhanced both the format and its functionality. the most recent update to the Gerber format was the addition of PCB metadata, a move that made the relatively simple image representation more intelligent. The current intelligent format is called X2, developed by Karel Tavernier, Ludek Bruckner and Thomas Weyn of Barco's PCB division Ucamco.
The Gerber format may not be the only choice for designers today, but the format has been widely used for many years, so it is important to understand the value that Gerber offers.
Checking design rules before converting to Gerber files
Using the design rule check (DRC) tool in your CAD software can prevent many problems from occurring. Once the DRC tool is configured, more information can be obtained. Are all layers included in the file? Is the spacing sufficient? What is the tolerance?
Just because the software can help design the board doesn't mean the manufacturer can produce it, and these answers provide a good basis for manufacturability. Design rules are checked before converting to Gerber files, and the manufacturer's capabilities and manufacturability are considered in this process.
Checking Gerber files
Converting to Gerber format provides a more comprehensive and simplified view of the design. Below are some categorized items that can be more easily checked when viewing a Gerber file and making changes if necessary.
Minimum Feature Size
When reviewing minimum feature sizes and the issues allowed by the DRC.
Find unintentional necking
Locate locations where the alignment is barely touching the pins
Find broken alignment locations or endpoints that barely touch
Finding pads that are too small
Eliminate unnecessarily small alignments or features that may add cost
Verify minimum hole sizes and locate unnecessarily small holes that could significantly increase costs
Feature spacing
Prevent gap problems before they occur. When looking at Gerber files, a sharper understanding of pitch types can be gained and problems can be identified such as
Between alignments
Between solder pads
Between copper
Between drilled holes
Between drilled holes and copper
Between solder pads
Look at each layer
This is the only way to confirm with the naked eye that each layer is correct. By doing this, you can speed up the quoting process and avoid cost overruns in the PCB production process. The following should be considered before submitting a request for quotation.
Has each layer been imported at the proper scale and size?
Is the number of copper layers correct?
Are the number of silkscreen and soldermask layers accurate?
Are the drill files reading as expected? Is it a single file or multiple files? If not, what is the reason for the discrepancy?
Are the drill files and Gerber files updated at the same time?
Do the drill holes and schematics match?
Were all filled areas updated before the Gerber file was generated?
Were the more costly blind or buried holes intentionally used?
For the questions under this category, just one error can cause problems for subsequent processes. The list of issues may seem long, but the potential return on investment from those few minutes is significant.
Checking the solder resist layer
When carefully inspecting each layer, be sure to pay attention to the solder resist layer. An oversight here will not only cause delays in delivery, but will also cause the PCB to not function properly.
Do all pins have soldermask openings?
The through-hole under the component should not have a soldermask opening, does it meet this requirement?
Are the soldermask openings slightly larger than the component pads (at least 0.004" larger)?
Are the plated through-hole pads 0.015" larger than the drilled holes to avoid hole breakout?
Leave clues to the manufacturer
Manufacturing instructions can determine whether a product will be produced quickly or delivered late. If the file name consists of confusing numbers or it is not at all clear exactly what service is required, look to the instructions for guidance.
Do the manufacturing instructions conflict with the order form?
Do the instructions call for unnecessary services?
Is the manufacturer unable to access the referenced documentation?
Does the design service selected include instructions that require inspection by a technician?
Not all quick sample manufacturing services offer human intervention, so when a conversion to Gerber format is selected, a few minutes should be spent checking the design and documentation before contacting the manufacturer partner.
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