One of the more thrilling events in track and field is the 400 Meter relay race. Understand, I don’t run; rather I enjoy watching. However, the most critical part of every race is the transferring of the baton to the next runner. I was watching a race some time back where one team was way ahead of the others and was coming around the final turn for the last hand-off. But, THEY DROPPED THE BATON, and they ended up losing. How frustrating that must have been. Everyone trained as hard as they could, and it all came down to a split second mistake near the finish line.
As we saw in a previous blog on “What are some common issues with PCB design workflows?”, the PCB design workflow is a process chain. It is a series of interconnected stages, inputs being used and modified by a resource to create an output which then functions as the input of the next stage, continuing until you reach the desired end or your goal. We need to understand the Tasks, Milestone (Verification) and Deliverables for each stage.
Gatekeeping and Design Reviews
An additional point about these stages and the chain workflow process: Each stage is viewed as a gatekeeping item—meaning that you do not move forward to the next stage until the previous stage has been fully completed and verified for the correct and complete deliverables. So many times, I’ve seen a project pushed forward with missing pieces and the full intention of “coming back to it” at a later date, and for various reasons it would never happen.
Early on in my career, I found Design Reviews difficult because we would get everyone in a conference room and throw the design up on a screen and ask “So what do you think?” Asking a room full of engineers what they think is a perilous proposition. The whole intent of those meetings was flawed because, really, what we were looking for were concise responses, something I can tell you never happened.
When we break down the design into stages with a set of Tasks, Milestones (Verification), and Deliverables, all we have to verify is whether the design is still on track with its original objective, what the deliverables are and if they are correct. Much simpler.
Significant Stages of Every PCB Design
The PCB design can be broken down into four major stages. The Component Creation (Library), Schematic, PCB Layout, and Output stage. These stages each have minor stages within them. While there may be other stages to add in particular situations, this article will cover the four major ones.
With each of the PCB Design stages outputs, the outputs are transferred as the inputs to the next stage. I cannot impress upon you enough the importance of these transfers. Just like our runners in the 400-Meter Relay, the transfer of that baton is the most critical part of this whole race.
Fortunately, Altium has got us covered with the transfer of information throughout these stages and the PCB Design Process. Whenever a transfer of data occurs between stages, you create an ECO with a full breakdown of every change that occurs. Within this ECO panel, you can easily select what changes you wish to do, then Validate those changes, and finally commit those changes. Just a point here, don’t be too quick to commit all the changes in a particular ECO without understanding what exactly is happening there. The rule you must follow is that everything from the beginning to end stays synced.
The Component Creation (Library)
The advantages of using a great software package like Altium is that you can create a unified Data model for components, which we will look at in more detail in other blogs. However, it suffices to say at this point that within that component is all the information required to do a complete PCB design: Name, Description, and sourcing, as well as the models of Schematic Symbol, Footprint, 3D models, and quite often simulations models such as SPICE or IBIS. A complete package.
The stage deliverable is all the components with all the needed information and models. A review of the component verifies it. The transfer of the data occurs when you lay down a component into the schematic.
A great tool in Altium to use at this point is its Item Manager Tool. It tells you all the sources of the components (finding of those Rogue Libraries) and the state of each component if they have been checked and verified.
The objective of this stage is to take the components created in the previous stage and wire them up using various methods—with the deliverables being a completely wired schematic that has been verified using the ERC and Connectivity setup and rules.
All this is a significant step in a PCB Design process, in which you push the schematic into the PCB.
With the transfer of the Schematic input PCB, there is a shifting of the information used. Earlier, in the schematic, you were using the component information and the Schematic symbol model. Perhaps even the SPICE Model (which is another subject). However, moving into the PCB, you now focus on the physical component of the Footprint and the 3D Model. This is also where your expertise as a PCB designer comes into play.
Your deliverable for this stage is an entirely laid out PCB, verified by using the DRC Rules.
Here, the verified PCB Design is transferred into your Output Job files. This will include the Fabrication and Assembly Drawing. Then, your two design packages of Fabrication data and Assembly Data. This is your final stage, and your PCB design is now complete.
When this workflow is followed, it is a beautiful thing. You can step into any point of the design knowing that specific stage’s deliverables, and see if it fully synced up with every stage before it. Be careful not to cut corners during this process and break this chain of data. I can promise you’ll have problems if you do.
Would you like to find out more about how Altium can help you with your next PCB design? Talk to an expert at Altium. You can also learn more about PCB Data Management in the PCB design process with Altium Designer® - the most advanced set of PCB design tools that you can get.
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