Utilizing a Checklist for PCB Design Finalization
Despite my hectic schedule, I try to spend as much time with my son. He’s at an age where football excites him and I promised to take him to the nearest field. But an absent-minded dad yields more disappointment than joy when I forget about bringing the ball after driving all the way to the field. It took a decent serving of ice cream and fries to pacify my heartbroken child.
Absentmindedness can strike anywhere. Fortunately, my son will forgive me and we’ll have many more afternoons playing games together (well, perhaps not as many as I’d like). When it comes to my circuits, though? Forget it—they don’t forgive a single mistake. That’s why I’ve made using a checklist part of my PCB design finalization process. This way, I can ensure that each board receives the same level of attention and eliminates potential oversight.
What Is PCB Design Finalization?
Now, if you’re rushing out manufacturing and Gerber files to send them to PCB manufacturers after getting all the nets routed, I can assure you that you’ve missed out an important process in PCB design finalization. PCB design finalization, in my world, consists of reviewing my board and documentation based on a series of checklists.
Even if you’re an experienced designer and confident in your skill, there are always chances of oversight that may translate into problematic PCBs when the fabrication is done. And if you just started your career in PCB design, it’s an unforgivable sin if you’re not doing the design finalization check. Okay, maybe a tad less dramatic but you get the point.
Common Issues When PCB Design Finalization Is Overlooked
There are so many things that could go wrong after the PCB is fabricated. For instance, a PCB could not be fitted into the mechanical enclosure because of a misaligned mounting hole or component placement. These may not affect board functionality, but they do cause a delay in the final production.
If you’ve received a call from the PCB assembler asking about the right location for certain components, you know you’ve neglected to check on the designators. Some designators may have overlapped while others are placed ambiguously.
But the real nightmare starts when you have functionality issues with the PCB. Traces that overheat because you’ve forgotten about conducting a current density check means a short lifespan on the copper trace. Noise coupling into analog traces because you forgot all about the current return path can also spell doom for your circuit’s functionality.
Ensure the copper trace can take the amount of current
Key PCB Finalization Checklists
After all the hours invested in PCB design, it will be foolish to neglect the finalization check. Here are some key aspects to verify before you get the design fabricated.
1. Mechanical Alignment
You’ll want to get more than the number of screw holes right. When mechanical alignment is concerned, precision is key, and that means double checking the positioning of each screw holes, board size, shapes, and components height. Utilize the 3D design viewer to get a good idea of how the assembled product looks like.
Mechanical precision matters in some PCB designs.
2. Thermal Dissipation
Thermal issues are a major concern and could affect the stability of the PCB if not taken care of. You’ll want to ensure that high-power components like regulators and transistors have ample dissipation via and a dissipating copper plane. It’s also important to keep heat-sensitive components away from these high-power components.
3. Ground Plane and Signal Separation
When you have mixed-signals of digital and analog on the PCB, you’ll want to be wary with the ground plane and what goes on top or below it. It’s good to have proper ground separation, but that would mean nothing if high-speed digital signals are routed over an analog ground. There’s a high chance for noise coupling over the analog components when this happens.
4. Designators Placement
You probably know by heart where all the components are meant to be, but the same cannot be said for the PCB assemblers or technician servicing the PCB. Check to ensure that the placement of the reference designators make sense and none are obscured when the PCB is populated.
5. Design Rules Check
The design rules check helps identify potential errors in what has been configured based on best practices. It is never a bad idea to give it a final run before you finalized the design for fabrication. You’ll never know if you have unintentionally altered some traces while you’re doing the final touch up.
6. Current Density
Sure, you’ve calculated and allocated sufficient trace width where you’d expect a high current path. But did you do the same for the return ground path? Current density issues affect power delivery to various parts of the PCB. You’ll need a good power analysis feature to verify that the power delivery is efficient.
You can save potential heartaches by using a good PCB design software that has a rich set of analysis tools. A power delivery analysis feature can help to clear any doubts on current density issues especially when it is integrated into your PCB Editor.
If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.