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What is PCB Routing?

PCB routing is a very important step when designing PCBs. It usually builds on the preceding step, referred to a placement, which tells the location of each PCB component. PCB design comes with a quality similar to that of games, most especially when we talk about routing. Here, we are dealing with lines, colors, and shapes on a screen and the goal is to connect everything before the space is used up.

Seriously speaking, completing a PCB design routing using PCB router bits could prove difficult. Some people may see it as a game, but it is not. Rather, it requires much skill and patience from the designer. How can PCB designers be sure of success while routing? Just like all other things, the secret here is making use of the best tools. Here, we’ll be considering some of the challenges that designers usually face while routing, and the routing tools that can be of help.

Using PCB Routing to Connect the Nets

The conversion of schematic nets to physical traces on PCBs has for long been the layout engineers’ major responsibility. This was usually done manually, making designers go through a drawing and redrawing process of their circuitry at enlarged sizes on gridded mylar sheets.

When you are ready, the circuit drawings will be photo-reduced and covered using opaque tape so as to create the right tool for fabrication. For years now, the requirement for performance of new electronics had to force the utilization of board elements that are smaller, which could not be created accurately by making use of tape. Due to this reason, along with many others, cause the evolving of circuit board designs to a higher level – which is the CAD system.

There have been many benefits since these systems were introduced. First, from schematic data, designers can transition automatically to layout data. To do this, they don’t need to input the spreadsheets’ connectivity manually. Another benefit here is you can automatically check clearance tolerance found between the boards’ objects like trace to pad or trace to trace.

With CAD tools for PCB design, the work produced experienced an exponential growth rate. Things changed, and soon the electronics technology that continues to evolve started to demand more tools for PCB design, most especially in the routing area.

Challenges Designers Face During PCB Routing

pcb cnc router

The connection of traces during the layout of printed circuit boards could be fun. Pulling these traces and then hooking them to ensure the nets are completed could be cathartic. Every day, simple board designs, which allow for basic routing having minimal rules, are beginning to disappear.  

Design rules with high speed, tight requirements for manufacturing, as well as other constraints requiring much attention rather than just connecting dots have taken their place.

Below are some of the challenges designers face when handling PCB bga routing:

Shorter times for design: To ensure the competitive advantage is kept, the times required for circuit board design should be trimmed back. Asides from this, board spins have to be scaled down. This will help in reducing prototyping expenses. By this, the designer will be more pressured to perform the routing correctly for the first time.

Analysis expectations: To perform the trace routing the right way, layout designers have to understand how their designs are configured before time. Asides from tools for your PCB cnc router, this also requires analysis and simulation tools.

Multiple design restrictions: There was a time where all the board’s nets had the same spacing rules and trace width, asides from ground and power, which needed to be wider. Different spacing rules and width for multiple nets have now replaced design rules.

Requirements for complex routing: So much routing on the high-speed boards of today will need some specific topologies and routing patterns. For example, DDR memory routing used in the past requires using the routing patterns of T-topology, while DDR4 and DDR3 require fly-by-termination topologies. More so, some impedance lines must be configured in order to match the stackup of the board layer, some differential pairs have to be routed together, as well as other requirements.

One way of managing all these routing challenges effectively is by getting yourself equipped with tools that serve advanced design requirements of circuit boards.

Tools for PCB Routing

Routing a PCB successfully requires more than just features of advanced routing. Routing begins long before laying down a trace. Therefore, we’ll begin this list with some other functions your tools for PCB design should have.

Component placement checks and aids: To route a trace the right way begins with placing the components correctly. This entails putting the right spacing between those parts to be observed. Also, signal paths must be optimized and the board must pass manufacturability checks. Just like circuit simulators, ripping up your routing in order to correct problems associated with component placement could have a ripple effect on the whole design which you would want to avoid at all costs.

Circuit simulation: These tools will not just help get your design to the market earlier by revealing the problems with the design before building a prototype, they will also assist your routing. Most high-density, high-speed designs feature tightly-packed trace routing. This is important for impedance control, signal timing, as well as other reasons. Whenever you need to reroute and rip up incorrectly captured traces, however, the whole design can be thrown off-balance. By using tools for circuit simulation, from the beginning, you can use the right schematic data.

Analysis tools: You don’t have to wait to build the prototype before analyzing how effective your routing is. The best process for your design is to utilize embedded analysis tools, which can be found in the design system of your PCB to check your power and signal integrity as you route. This allows you to make changes to errors made while working, rather than go back to redesign the board.

Design constraints and rules: You don’t just have to control the trace spacings and widths for multiple areas and nets, however there are some design parameters that have to be managed too. Constraint managers will give you some control over the design’s physical and electrical attributes. With this, you’ll be able to set up length matching, trace lengths, differential pairs, as well as many other constraints and rules.

Having all these features, you will be ready for your PCB router machine. Below are some of the routing tools you’ll find very useful:

Slide routing: This grants the ability to clean traces quickly, grab trace segments, and pull it to your desired location. Even better, is its ability to move other objects such as traces and vials from the way while sliding.

Manual Interactive Routing: For sure, you’ll always have to hook some traces up manually. Your tools for design should allow this to be performed easily with different editing options to help in complimenting your routing.

Differential pair routing: Differential pairs have to be routed together ensuring that the spacing is consistent between the pair’s traces. These routers actually work in line with the differential pair rules, which are set up for the spacing and trace width values.

Fanout routing: This is also referred to as escape routing. With this automatic feature, you can pull out traces from high pin-count parts quickly and then connect them to vias.

Auto-routing: Auto-routing can take many forms. This ranges from single trace to the full batch type. Full batch means that the whole board will be routed.

Bus routing: This is another great and useful feature where some traces can be grabbed and then routed together.

Cleanup routing: Several tools that can clean up your board’s routing are available. Some cab mister your traces’ corner, while some others will get rid of unnecessary segments and jogs.

Trace tuning: The routers work in line with the constraints of the design. It also helps in increasing its length overall by adding some serpentine segments to your trace.

There are lots of other routing features to be used, and you can call them different names with respect to the tools used for the PCB design.

How to Makes These Tools Work

When a PCB design system has more routing features, then you’ll have more capabilities to get this job done. Usually, designers combine these tools to achieve the results they want to see in their design.

For example, you may wish to begin by making use of the Fanout editor in doing the escape routing. Then you may want to utilize the interactive router with your set up constraints to route the controlled impedance lines and differential pairs at the right spacing and width and in the right locations.

After this, you may decide to put in your main routing using different auto-routing features and then tune up your transmission lines (high speed) to the right lengths making use of the tuning features. Finally, you will make use of different combinations of cleanup tools to optimize the routing, which has already been done using the pcb depaneling router.

Conclusion

PCB routing is a very important step when designing PCBs. It usually builds on the preceding step, referred to a placement, which tells the location of each PCB component. Whatever approach you decide to choose for your routing will depend on what your PCB design needs.