PCB engineers share the process concept of PCB design

PCB engineers share the process concept of PCB design

PCB and SOC packaging design is a little like this, which means that it is really a difficult problem consisting of parts, circuit interfaces, power planes, thousands of signals, via conversion and many design rules that need to be combined and perform electrical sound and have the required performance, and can also handle the constraints and restrictions of mechanical shape factors.

Cornerstone of PCB design

The importance of following a good input list

Having an input list allows engineers to think about and create a form of communication in the form of records, and can basically make the ball roll. The list can define many things and provide a starting point for us to start the PCB design journey. This is also the time for engineers to reflect on what they are looking for in the design. So far, engineers have been thinking about electrical problems in most cases, and have been immersed in schematic and part search (I hope so). Now is the time to start physics, ha ha. This means starting to think about how the electrons will flow on the PCB and what is needed.

I have a list of things I use, which contains the basics. The more design you do, the more it boils down to muscle memory. If you are a layout engineer, your mind will be more bent, and now you will think like a PCB designer. For example, you might now consider reference codes more than part numbers. You will do the feasibility study early, and enter the list to start the phase. The basic items required are BOM, mechanical input, wiring/design rules, total thickness, impedance requirements and minimum spacing components to help define the required through-hole structure and do BGA math.

Collaboration with MCAD is critical to starting the project. It is important to be consistent with the mechanical requirements from the beginning. The total board thickness, connector position/rotation, placement exclusion zone and mounting hole must be precisely defined and considered early in PCB design. This is the foundation of the building you are going to build. Frames are physical constraints and dimensions that can be used to accommodate the design, so you can see that accuracy is critical to the success of the design. I have seen in the past that the mechanical plate outline from MCAD displays the bottom view and enters ECad in the top view, which will affect the placement of parts. Do not do this. Make sure your view is correct, and share. idf or. idx files as much as possible. If you have this ability, include the same step model files. This will ensure successful MCAD collaboration. In addition, you may now need to negotiate where to move the radiator mounting holes, but assembly placement will also determine the limits. For example, if it is recommended to place your high pin count BGA in the corner, and it completely fills the signal, then it is time to push it back, because you will be trapped in trying to route from the corner and need more signal layers

Importance of routing rules

Wiring or design rules are the key to control PCB design. I often refer to the recorded rules as the train tracks that trains must pass. Rules are defined in a document, and many e-mails are changing every day or every hour and difficult to track, so it is easy to deviate from the track and miss or forget projects that are critical to design performance, and allow PCB designers to communicate and provide legacy documents. The concept of rules in the form of documents is used to populate rules in CAD tools, usually called constraints or design rules, and the design must follow these rules. This includes the physical and electrical rules that the design will follow to meet timing, noise and manufacturing requirements.

High speed routing and simulation - power supply concept

Now that the design has begun to take shape, the rules have been in place, and the layout and power plane are being defined, it is a good time to lay out the most critical interfaces and the most challenging high-speed circuits (if they exist in your design). It is a good idea to have a stack that applies to the entire design. Using the standard through-hole size and trying to achieve a good yield aspect ratio, it is time to test the circuit, layout and wiring, and then simulate. Yes, once the critical network cabling is completed, the simulation will now be carried out to see if you meet the requirements for optimal performance. It is at this point that you may find that you need different stack or through-hole configurations. For example, if you try to reach 12GBPS, and you use through-hole on a board with a thickness of 0.093 on 18 layers, you may find that performance is achieved through excessive reflection caused by stubs. You may need to consider another option, such as blind and buried holes or back drilling or different board stacking and interface options. The circuit board assembly and processing manufacturers explained that the circuit board engineers shared the process concept of PCB design.

The four steps I described above should lay the foundation for a successful PCB design framework. My experience following these steps has helped to produce consistent results. I think it is important to develop the framework first. Next, is the simulation successful? Do you need to change the PCB design board configuration or through-hole structure or through-hole size or manufacturing materials with low Dk and low loss? You can learn a lot from the simulation, which will help pave the way forward.

Once the simulation or calculation is carried out, and after the initial critical routing/adjustment of the high-speed interface, all these items should disappear. So, if everything is normal, what is the next step? Where are we going from here? Confirm stacking? Design organization?

This is what I will discuss in Part 2:

Stack definition for each technology - track width target

Organize your networks and constraints as well as class to class rules and overconstraints.

Layout planning according to design rules

Transition and planning of routing using Via mode/layout

Advanced SOC chip design and how to plan PCB design using SIP or SOC.