When committing to PCB, these key strategies will help you get it right...
You're just about to make the most important decision of the design process; committing the PCB from Easy-PC to a set of manufacturing outputs - but have you got it right? Here Iain Wilkie, from Wilkie Electronics discusses simple key strategies employed at the point where the design is ready to be manufactured.
Take control of styles and layers in your Technology
Before you press the Plot button, ensure that you have a full set of layers that will be utilised at the plotting phase. It is easy to forget non-electrical layers such as solder resist and mask layers. Although Easy-PC can automatically create solder resist and mask layer plots for you, by manually adding these layers, you can also add layer shapes to create additional detail that can be used on the layers. As an example, you need more solder mask for BGA thermal pads that have been created from copper shapes. Pad exceptions in the Pad Styles Technology dialog will enable you to size pads ready for plotting. Save these Layers and Pad Styles to your Technology files for use on subsequent designs.
Sanity Checking in Easy-PC
Checking is everything, the tools are there in Easy-PC, so use them! It often surprises me when I hear of Easy-PC users not checking even basic items such as Spacings. If unsure about what Spacings you should use, ask your manufacturer. It's an obvious statement but they know what they manufacture. They'll also advise you on costs; generally speaking, the smaller the tracks and gaps (spacings), the more expensive the board will be. Ask yourself if you really need very small tracks and gaps when larger ones are fine - and cheaper!
Track lengths, especially when designing differential pairs, are another essential facet to introduce and check. By simply defining additional Net Classes and Track Length rules for critical nets, a report can be run to verify that these nets adhere to your rules. Again, another very useful feature in Easy-PC is the Net Match feature for Spacings. These will ensure critical nets are spaced at the required distance from each other.
Verification is everything
When creating multi-layer designs (and even 2-layer designs) your verification stage of the design is vital. If creating a design with more than 4-layers, this becomes even more critical, getting it wrong now will mean a big expense in time and money once the board is produced.
Running Design Rules Checking (DRC) is mandatory, and one of the last operations before hitting the 'plot' button. The Copper Shape Verification check is essential if your design contains poured copper areas and is quite often overlooked. The Nets check should also be used; Net completion and Dangling Tracks must always be checked and resolved. The Track Lengths check should be used if your design has critical nets defined.
Outside of the DRC dialog, use the Connectivity Check report to check for split nets and single pin nets. Again, errors here can cause the design not to be manufactured correctly further down the line.
3rd Party Reassurance
Finally, you are satisfied that all your checking and verification is as expected and your design has no perceived errors. My final sanity check is to export the PCB design as an IPC356A testpoint format file. This is done alongside the export to Gerber and Excellon. This file is read into the Fab3000 program along with the Gerber files. A check using a netlist derived from the Gerber data is then compared and analysis provided. At this point, I am satisfied that I have done everything I can to ensure my designs leave me ready for manufacture.
About the Author
Iain Wilkie is the Managing Director of Wilkie Electronics based in Perth, Scotland. Iain has over 40 years experience in the PCB design industry, many of which have been using Easy-PC.
If you would like to contact Iain, his web site is: www.wilkie-electronics.co.uk
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