You know the story of RMS Titanic and how just before midnight on April 14th, 1912, it struck an iceberg in the Atlantic Ocean and sank. What you may not know though is how one small item may have saved the ship from sinking. During the inquiry, one of the surviving crew members who was a lookout reported that they did not have a pair of binoculars to use in the crow’s nest. When asked if having the binoculars would have made a difference or not, he replied that they would have given “enough time to get out of the way.”
The tragic thing is that the binoculars were there, they just weren’t accessible to the crew members who needed them. According to one story, another crew member who had been replaced just before the ship sailed accidentally took the key to the binocular locker with him. Without the key, the lookouts couldn’t get the binoculars and therefore weren’t able to see the iceberg in time for the ship to steer around it.
It is often the little things that we forget to check that end up causing the biggest problems. This is why we have processes to check for those small things that may end up sinking our boat or causing our printed circuit boards to be non-manufacturable. Traditionally you will check for errors related to how the circuit board will perform by using design rule checks (DRCs), and the manufacturer will check for errors related to the manufacturing of the board by using manufacturing rule checks (MRCs). We will see here how these checks need to be used together in order for the finished PCB to make it through manufacturing without errors and match up with its bill of materials.
Manufacturing Rules Checking
The PCB manufacturer has always checked the board for manufacturing rules violations, and for a long time that was the only place that those checks happened. The older layout tools that we used would run the traditional DRCs, but they weren’t set up to run all of the checks needed to make sure that the PCB could be manufactured. Once we finished the design and confirmed that the board had passed its DRCs, we would then turn it over to the manufacturer and they would run MRCs with their own specialized tools.
I was always frustrated when one of my designs was rejected by the manufacturer because of a problem that I couldn’t check for with my layout tools. Some of these unchecked items included searching for solder mask slivers, acid traps, or silkscreen to silkscreen clearances. A lot of time was wasted waiting for the manufacturer to check my design and then report back to me so that I could make corrections.
Full design rule checking is the best way to get your board through manufacturing with no errors
Design Rules Checking
DRCs, on the other hand, are those violations on a printed circuit board that will affect its electrical functions as opposed to how the board is manufactured. For instance, an incorrect size of the conductors on a PCB, such as trace widths or the spokes of a thermal relief pad, can cause the board to not work as it should. Objects like these are among those DRC items that typically don’t have any effect on the manufacturing of the board. There are however other DRC items such as object clearances between traces, component pads, or area fills that will affect both the electrical functionality of the board as well as its manufacturability.
DRCs are an essential design tool and should be available to you as an online function while the board is being laid out. Prevent your design errors from occurring due to components being too close together, or net shorts due to traces touching each other with real-time rule checking in your layout tool. In addition, at any time during the design, a batch DRC pass can be run as well. You can use it to catch any DRC errors that were ignored during design, or if the online DRC was not used.
The layout check design rules menu contains a complete set of DRCs and MRCs
Your Bill of Materials Will Also Benefit From Rule Checking
The best checking solution is enabling you to check all aspects of the PCB design at once. This includes both the traditional DRCs and the MRCs as well. Fortunately, the MRCs that used to be only available as part of the specialized tools owned by the manufacturers, are now included in the DRC options of advanced PCB layout tools. Circuit board designers are able to detect MRC errors along with DRC errors and correct them all at the same time.
With the PCB design entirely checked for errors and ready for manufacturing, you are able to create the bill of materials (BOM) with confidence in its accuracy. CAD tools today have functionality that allows the creation of the BOM with different formats, groupings and other customizations that make your BOM part of the design process instead of a simple report. Even finding a specific part on the schematic can be easily accomplished by selecting the part from the BOM.
If you’re looking for both advanced rule checking functionality and advanced BOM creation utilities, then consider PCB design software like Altium Designer. It has Active BOM which is more than an independent or auxiliary document, it is part of the entire unified design platform giving you more control and power with your design. Find out more information by talking to an expert at Altium.
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