Physical Multi-Board Assembly Strategies Created with Superior PCB Design Tools

June 26, 2019 Cadence PCB Solutions

Multiple blue circuit boards in a physical multi-board assembly computer system

 

As the electronics market becomes more and more competitive, PCB design is evolving in order to reduce the expense and time of circuit development. For the PCB designer this has resulted in a change to the more traditional approach to circuit board design. Where designers used to have the luxury of long design cycles and multiple prototypes to develop a single board, the emphasis now is on developing full system design with less time and fewer resources.

To keep pace with this new paradigm, PCB designers are finding that they need to become experts in designing for physical multi-board assembly systems in addition to regular single board designs. This will require new skill sets for the designers, and enhanced PCB design software systems to give them the tools they need for the job. Fortunately, the tools to handle these requirements are already here and ready to be used. Here’s how you can leverage these tools to your advantage in full system design.

Physical Multi-board Assembly and How it Impacts PCB Design

PCB design used to involve many more design iterations and physical prototypes than what design schedules allow for today. Design tools were more isolated in how they worked and required a lot of personnel within separate design teams for their operation. Communication between design teams wasn’t always the best and relied on elaborate tracking systems and time spent in meetings. The mechanical team might make a change to the system enclosure, but the details might not get to the PCB layout team in time for changes. This would result in additional time for redesigns, another round of prototypes, and more expense. The question then was, with the need to get product to market sooner, how can these problems be resolved?

The answer was to create efficient PCB design tools that were able to design multiple circuit boards that were part of an entire system, and not just individual board entities. Not only did that help to design better boards and systems but it also helped to improve the communication between design teams. In order to accomplish this, the design tools were enhanced with the ability to seamlessly work together with other systems such as mechanical design tools. With the ability to import the mechanical design constraints of the system along with the other system board designs, PCB designers now have the advanced tools they need for full physical multi-board assembly design.

Full System Design All Under Your Control

Starting from the top down, today’s PCB design systems are able to model the entire system at the top level of the schematic with blocks representing the different system board designs. As you descend into each block you will be able to work on the schematic for that specific design, capturing and simulating schematic circuitry as you have always done.

In addition to board level simulation though, another advantage to the top level system design is that you also have the ability to perform circuit simulation of the entire system. This gives PCB designers much more visibility into their design so that they know how each individual part of the system is interacting with the rest. In addition, this top level design approach provides the ability to assign design tasks and responsibilities to team members. This helps to improve department communication and establish a more precise design workflow.

As you move into PCB layout you will work with each individual board as you always have, but with the enhanced capabilities of the design tools you will have additional features available to you as well. You will be able to work with your design in a full 3D environment giving you a new perspective for checking your placement for clearance violations. Additionally you will be able to import the system enclosure data from mechanical design team, as well as other system board designs. This will give you the ability to do a full form, fit, and function verification of the entire system.

With a PCB design system that is built for full system design, you can then start focusing on some of the details that were more difficult before. For instance, intra-system board connectivity is something that was difficult to work with from an individual board design perspective. Now designers have the tools they need to better solve some of these problems by being able to work with multiple boards at once.

 

Image of a man with his finger on the cpu of a full system design

With the proper PCB design tools, full multi-assembly system design is under your control

 

PCB Design Considerations for Physical Multi-Board Assembly

With the capabilities offered by today’s advanced PCB design systems, designers have the ability to focus more on areas of multi-board design that had previously been more difficult when working on a single PCB layout.

Starting off, choosing connectors and having knowledge of the connectors available to you will be invaluable in your multi-board assembly. After, learning how to properly discuss with mechanical teams and manufacturers for assembly instructions will suit you well as will understanding material considerations for your board designs. Finally, it never hurts to refresh yourself on multi-board design techniques.

Working with Connectors in Multi-Board Design

There are several considerations that you should look at before selecting the connectors you are going to use for your multi-board design. These include functionality of the circuit where the connector used to be, what the connector will be used for, how many pins are needed, and signal performance requirements. You also need to be careful to lay out your multi-board designs so there is a consistent ground return path for signals between boards through the connectors. Some connections will require multiple ground pins on the connectors while others, such as differential signaling, will allow you to reduce that number.

For more information on working with connectors in multi-board designs, read about it here.

For Multi-Board Applications, Choose High Power Connectors for PCB

Multiple high-speed PCBs in full system designs will be conducting more power and have more stringent signal integrity requirements. To make sure that you have the most reliable intra-board connectivity, you should choose high power connectors. You also need to make sure that you have designed your boards to handle the additional power and signal requirements that these connectors will be carrying. You can have some potentially serious problems if your board design doesn’t match the current that your connectors can handle.

Here is some additional information on high power connectors for your multi-board systems.

 

Screenshot of physical multi-board assembly 3D layout in Cadence tools

With the right 3D tools, working with multi-board system assemblies is more efficient

 

Designing for Multi-board System Assembly Configurations

One advantage of multi-board systems is the ability to separate circuit functionality onto different boards. This will give you the ability to have a digital board and an analog board, and not have to deal with the complexities of mixed signal designs. Linking these designs together will require care, and it is important that all system boards be grounded to the chassis. You also need to exercise caution when connecting signals between digital and analog boards. It is very similar to routing traces over a split plane in a mixed signal board, and you might introduce crosstalk into the system if you aren’t careful about using shielded cables for the intra-board connections.

If you’d like to learn more about multi-board system assembly, read about it here.

Selecting PCB Materials for High-Frequency Applications in Multi-Board Systems

Selecting the correct material for your multi-board application is critical. The standard materials that designers are used to, such as FR-4, may not have enough insulating properties with the additional power, voltage, and heat of multi-board systems. There are several materials out there that your PCB fabricator can use in combination with other materials to give you the best results for you specific needs. There is more to consider than just performance however, and cost and fabrication ease are important. You need to make sure to consult your manufacturer for the best material options for your multi-board system.

Read this for more information on how to best select PCB materials for high-frequency multi-board applications.

 

Screenshot of Cadence cross-section editor used in physical multi-board assembly designs

The Cadence Cross-Section Editor helps with the selection of PCB materials

 

Multi-Board Enclosures and System Design Techniques

Multi-board assemblies start in the schematic. You need to set your design up with block symbols that will represent the individual PCB designs projects. Each individual board represented in the top level schematic can be worked on by one or more team members. This will give the maximum advantage to both schematic capture and PCB layout. In addition to circuit simulation of each individual design, you can do a simulation of the entire system.

Read here for more information on multi-board system design techniques.

PCB Design Tools that Make Full System Design Possible

Today’s PCB design systems is what makes physical multi-board assembly and full system design possible. With the ability now to start at the top level of the schematic and work down through the design into the individual PCB layouts, designers today have the advantage in their work like never before.

With Cadence’s Allegro PCB Designer you have the option for concurrent team design to improve communication and involve others in your design process. The interactive 3D canvas and seamless mechanical collaboration will also give you the ability to work with system enclosures and other PCBs for complete control over how all of your system boards will work together. In addition, Allegro PCB Designer gives you the state of the art design system functionality that you expect from Cadence such as signal integrity analysis, constraint driven design flow, and circuit reuse features.

 

Screenshot of multi-board 3D design

Working with multiple boards in a 3D environment is critical for the success of full system designs

 

You need the best PCB design tools available to keep pace with today’s accelerated design cycles and the requirement to get to market sooner. Allegro PCB Designer is the design system that you have been looking for that will support your physical multi-board assembly needs.

If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.

About the Author

Cadence PCB solutions is a complete front to back design tool to enable fast and efficient product creation. Cadence enables users accurately shorten design cycles to hand off to manufacturing through modern, IPC-2581 industry standard.

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