Gathering your information and configuring your data is essential in multi-board design.
Schematic capture and PCB layout is still the same, but now involves working with all the system boards in the same environment.
Multi-board system design gives you the ability to check and simulate the entire system instead of just a single design.
To learn more, what are the specifications required in system connectors, and how does a designer optimize connectors for electronic designs?
Multiple circuit boards and other components inside of a system
Designing a printed circuit board can be a complex project. Translating the requirements of the device into working circuitry that supplies the needed functionality involves a lot of design decisions. The size, shape, and performance of the PCB have to be counterbalanced with standards, schedules, and cost requirements. It is a major puzzle that has to be carefully put together, and fortunately, PCB designers have become very good puzzle solvers.
Now a new piece of the puzzle has emerged with system design of multiple PCBs, only it’s not so much of a “piece” as it is a whole new puzzle. System design used to involve many participants and tools, but now is becoming more and more the job of the PCB designer. This is good in that all system design decisions can now be centralized, but it does put a lot more responsibility on the PCB designer. With the following multi-board PCB design process overview, we can offer some insight into how to establish a useful workflow for system design.
Multi-Board PCB Design Process Overview Starts with Good Information
Understanding how a single printed circuit board is going to fit into and interact with the system that it is designed for requires a lot of information. Now that you are working with all of the boards of the system, the need for complete information is even greater. For instance, are the boards going to be manufactured together in the same panel? If so, then you will need to plan out their layer stackups accordingly.
Not only will you need to work together with all members of your design team to make sure that the software and mechanical requirements are clearly stated, but with your manufacturers as well. Multi-board design is intended to reduce development time by organizing multiple designs together within a single environment. To ensure that you benefit from this new design paradigm, you need to make sure that your processes and workflows are updated and ready. The last thing you want is to slow down your multi-board design process with single board design practices and procedures.
Schematic Capture in Multi-Board Design
You are already used to working with a single board schematic, and you’ve probably worked with hierarchical schematics as well. System schematic design is similar to working with hierarchy, but instead of the upper-level blocks representing different areas of circuitry, they will represent different circuit boards instead. The process here is to link your individual schematics together in the system schematic. You will still design and simulate your schematics at the individual level, but you will also be able to simulate at the system level as well.
Organize and Set Up Your Design Rules
A portion of every PCB layout is setting up the design parameters and the rules and constraints of the design. With a multi-board design, you need to do that with every layout that you are working with. This will cover everything from PCB part libraries, layer stackups, and design rules. The more that you can do to maintain consistency between the different layout databases, the less you will have to adjust when shifting between designs.
If you haven’t done so already, you should consider saving different board outline templates, layer stackups, and design rules off in a central location like your PCB library parts. This will help your design organization, and enable you to get started on your layouts much sooner than if you have to re-enter all of this information manually for each design. Working with templates and copies like this will also help to reduce the chance for human error when inputting the same rules over and over again.
With multi-board design, you can view added boards to your design as with this DIMM
Multi-Board PCB Layout
PCB layout will be very similar to what you are already used to because you still have to design each board separately. The advantage though is that you can view the different boards and mechanical elements of the design to verify your parts placement while in layout. This will help you to avoid clearance problems between parts, enclosures, or other objects that have to mesh tightly together in the final system. With some CAD systems, you can also split the work up and assign different portions to other team members as needed, all while staying within the confines of the multi-board system.
With the 3D capabilities of your CAD system, you will also be able to get a clear view of how different aspects of the design will look when put together. Not only will you benefit from the 3D obstacle checking, but you can visually verify portions of your design that you haven’t been able to do before. For example, you can see how a connector is going to fit onto your board along with the other boards, mechanical obstructions, and system enclosures. It may pass your design rule checking, but once you view it you may realize that there isn’t any room for someone to physically reach in and access it.
Full System Design in Review
Throughout the multi-board system design process, there will be different opportunities for checking the boards against each other and the entire system. The 3D modeling capabilities of a multi-board system will allow you to virtually prototype the boards of the system before you commit to an actual build. This can save you a lot in time and money over the standard prototype building process. Meanwhile, the connectivity checking between the PCBs in a multi-board system will allow you to verify that your intra-system connections are correct without having actual hardware in your hands to physically test.
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