It Takes Two: Modern Circuit Board Design

Today, the entire world is abuzz with the Internet of Things (IoT) and smart, connected products.These interconnected trends are affecting practically every industry, transforming business models, and impacting almost every phase of a product’s lifecycle.

At the center of these offerings sit circuit boards and the software that runs on them. Together, they act as the brain of the smart, connected product. They process sensor data. They send signals to actuated components. They communicate with IoT platforms.

Developing modern circuit boards, however, is no simple task for an engineer. In fact, it requires tight coordination between the electrical engineer and mechanical engineer on several fronts. We’ll be exploring those activities in this post.

Electronic Design: A Job for One

While the development of a circuit board requires many aspects of collaboration between the electrical engineer and the mechanical engineer, electrical design is not one of them. Mostly, the creation of the schematic is a lone job carried out in an Electrical Computer Aided Design (ECAD) application. The only aspect that might require some coordination is the selection of components, which carries some implications into the form and fit characteristics of the board. Most of that, however, is determined by the processing requirements or by the architecture developed by system engineers.

Form and Fit: Board, Assembly, Enclosure

The real points of coordination between electrical and mechanical fronts happen during the layout of the circuit board. Sometimes, the mechanical engineer will provide the outline for the board, developed based on the space that is available in the 3D mechanical assembly built out in a Mechanical Computer Aided Design (MCAD) application. Sometimes, there is more flexibility here, where the focus is on claiming a space for the enclosure instead of the board. Either way, the electrical and mechanical engineers must coordinate the outer boundaries of the board before components can be placed in the layout.

Once that outer boundary is defined, the electrical engineer can place components as needed. This is done in a two dimensional (2D) layout in the ECAD application. This populates a three dimensional (3D) assembly of the circuit board in the MCAD application.

Depending on the constraints and requirements, a lot of compromise and coordination happens in this phase. The mechanical engineer might need a tall component moved because of an interference. The electrical engineer might want to move it somewhere else because a trace connecting that component might violate a minimum length design rule. Modern design of circuit boards isn’t a linear path. It is iterative. It is collaborative. All that is because many constraints must be negotiated together between mechanical and electrical engineers. Associativity between the ECAD and MCAD applications is key.

Electronics Cooling: Don’t Slag the Chip

Form and fit, of course, aren’t the only considerations when developing a circuit board. Modern circuit boards can use an immense amount of electrical power in a very small space. As a result, the processors and other components used on the chip can get hot. Extremely hot. So hot that it can not only affect the performance of the board, but some components can melt.

On this front, the electrical and mechanical engineers must ensure that heat generated by the circuit board is evacuated out of the enclosure, the casing that houses the circuit board. There are many approaches to moving that heat including natural convection, forced convection, liquid cooling, conduction and a few other approaches. Other options include moving those electronic components around to affect heat flow. Yet another alternative is to change the design of the enclosure in an effort to improve how heat leaves the space.

There are all sorts of calculations engineers can perform by hand to cover these kinds of physics. However, this is where fluid and thermal simulations are particularly powerful. These analyses can accurately determine the peak temperature of those electronic components, offering insight into where the circuit board might overheat. Furthermore, these simulations can be run, again and again, with each change that the engineers consider. That immediate feedback empowers engineers to make better decisions.

The Alternative: Physical Prototyping

Now, let’s be clear: the application of simulation isn’t required. Alternatively, engineers can develop physical prototypes to check for these issues. For each issue, you can make a change and build another mockup.

The implications, however, of following this path can get ugly. Prototype boards can take some time to get into your hands. Building that out, time and time again can eat up a significant amount of time in the schedule. And if there’s one thing about today’s smart, connected products, it is that getting them to market as fast as possible is paramount.

That is why empowering engineers with tools to coordinate and collaborate is so key. They can not only identify these kinds of issues but avoid them. That, then, allows the company to accelerate their plans.

Recap

• Circuit boards, and the software that runs on them act as the brain for smart, connected products.
• Electrical engineers can develop the design of the circuit board, the schematic, on their own in ECAD applications.
• Developing a circuit board’s layout is a back and forth affair between the mechanical and electrical engineer based on its fit into the enclosure and the enclosure’s fit into the product. Associativity between the ECAD and MCAD applications is key.
• Modern circuit boards generate a tremendous amount of heat. Tradeoffs on the placement of components–means of dissipating heat, design of the board and of the enclosure–all factor greatly in successfully managing the thermal traits of the design. Fluid and thermal analyses provide powerful capabilities to explore alternatives on this front.
• An alternative is physical prototyping. However, this can be incredibly costly, both from a monetary and budgetary perspective. Most companies simply can’t afford that kind of cost in their development process.

Well, folks, that’s my take. Would love to hear your thoughts in the comments below.