PCB Data Management in the PCB Design Process
Learn about PCB data Management and how it interrelates to the PCB Design process and roles of everyone involved.
TOPICS IN THIS SOLUTION
According to the business dictionary, a process is defined as:
“A sequence of interdependent and linked procedures which, at every stage, consume one or more resources (employee time, energy, machines, money) to convert inputs (data, material, parts, etc.) into outputs. These outputs then serve as inputs for the next stage until a known goal or end result is reached.”
That is an outstanding definition because it is a concise detailed description to the individual parts of a process, the stages, Resources (Roles), Data Input and Data Output and the end result (Objective). We will be using this as the springboard into specifically how this relates to PCB data Management and more importantly how it interrelates to the PCB Design process and Roles of everyone involved.
There is a common practice in the world of computing called Pipelining, also known as a data pipeline. It defined as a set of data processing elements connected in series, where the output of one element is the input of the next one. That is exactly what we are creating here with our PCB Data system and our PCB design process. A data Pipeline. Data is inputted into one end of the pipe as the starting point. Feeds into the process. Along the way individuals with specific “roles” according to our earlier definition by the business dictionary convert those inputs into outputs to keep it moving down the pipeline to the next individual. Until it reaches the end where it comes out the other side as a finished product of a completed and hopefully working PCB design.
As we now really start to “Eat this Elephant” let’s keep in mind that the objective is not the process itself, but rather to meet the end result. Many times, we get lost in the “how” when we should concentrate more on the “What” and the objective we are trying to reach. By looking at it as a pipeline, we can easily than define the required inputs, Roles and expected outputs at any given location in our procedure. But a concern is since everything is intertwined and connected, if the input is not good… no degree of massaging of that data will make it correct. Better said, if the pipeline is connected to the sewer system, don’t expect flowers to pop out the other side.
The very life blood of every PCB design is the electronic component. Everything starts and ends with that. The integrity of a design has a direct correlation to the integrity of the components.
At one time because electronic systems were not as complex as they are today, components were much simpler. They consisted of a schematic symbol, a footprint and a few basic parameters. Matter of fact a common practice was to simply copy a component and simply change the value and use that exact same part throughout the design. Over time, more complex components were needed with much more information and details attached to support the cutting-edge systems.
What we now have can only be described as a treasure trove of information for components. Much of this is being readily available at our fingertips.
The modern components in our library have several very important facets to them. All these individual parts are very important because it will be this information that will be filtered to everyone involved in this process.
The typical electronic component should at a minimum the following information:
An Electronic symbol is a pictogram used to represent various electrical and electronic devices. Every component has its depiction and when placed on the schematic with other parts and the appropriate connections between them form the Schematic sheet of the electronic circuit. Some components and circuits can become very comprehensive with thousands of components with 10,000’s of connections.
This is known by various names either footprint, decal, land pattern but they are all the same thing. It is the physical component with arrangement of copper pads to make connections between the various components. What is vital between the schematic symbol and the footprint is that they match according to the number and identifier for each pin. The Footprint is made up of several items which include: Copper Connections (Pads), 3D Model usually embedded into the part, Silkscreen, placement courtyard (on a mechanical Layer) and other mechanical information as needed.
A very important tool for the Electronic Engineers. They have been become more popular as the need has arisen to simulate a certain circuit to verify its correct operation without having to fabricate and assemble the PCB. The major downside with the Circuit Simulation models is for the more complex Integrated circuits are many times proprietary information and is not available. So, fully simulating a circuit because difficult.
This information is imperative to verify the mechanical design of the enclosure or any mechanical matters. As the push continues to make things smaller the Mechanical Computer Aided Design (MCAD) many times ends up driving the design. We will be seeing coming up, that many sources of 3D Step Models are available including such sites as GrabCAD and 3D Content Central, but many part Manufacturers are now providing the needed 3D model as a part of the component information.
This is where the rubber meets the road. These details of a component. The specifications regarding a specific component. Depending on the type of part, there can actually be 100’s of various parameter details.
Once we determine all the other important facets of a component we must look at this area of Sourcing. Where and how will it be purchased? As we will see coming up, this becomes a very important area. Because we must use parts that we can get. As we saw in the shifting paradigm, of the crisis of part shortages that is becoming more and more difficult. One of the ways to manage such a huge problem is to through information.
Lastly, attached to each component should be its supporting documentation. These would be the datasheet, Technical notes, Rohs, etc. This will especially be helpful once the review procedure is conducted to audit the component as it’s verifying documents.
The foundation for much of this section will be the 5-Pillars that were discussed in the previous chapter. The procedure to start a PCB Management system. Is broken into two stages. The first being the acquisition, storage and the review of the Information. That must be done before any component should be used. The second stage is the usage and maintenance.
Having a reliable resource of information on a wide range of Electronic Components is invaluable. There are many component suppliers such as Digikey, Newark or Mouser, that are good but they only cover the particular components that they supply. But one of the best that I personally have seen that covers all the wide range of vendors is a company called Octopart. Hoping to make this as practical as possible. If you conduct a search on an ATSAMA5D31A-CUR which is a MCU 32-bit SAMA5D3 ARM Cortex A5 RISC 160KB ROM 1.2V 324-Pin LFBGA T/R. First thing that you notice, is the long list of the vendors that supply this component and the present live data. Which includes, Quantity on hand, price and price breaks.
But in addition, also provides everything else you would need. The MFG Page, CAD models which would be the Parameter Information, Schematic Symbol, the Footprint and the 3D Model.
If that wasn’t enough it also has the attached Datasheet. What more could anyone ask for?
Once we find the needed component and its information, need to move all this into our PCB Data system. This is where we find out how strong our building really is. Let me walk through an example of how it was done. Can basically summed up in 3-words…. COPY AND PASTE… lots of copying and pasting. Than creating the schematic symbol and footprint…. Than hoping that you could track down the 3D model. It was tedious and very detailed with lots of opportunities to make mistakes. Also, if you were placing a complex component such as this ATSAMA5D31A-CUR. Even with a rather moderate pin count of 324, it would still take hours to just do such a massive schematic symbol with the naming of each individual pin.
That entire process has been simplified. Now it is as simple as conducting a search for the needed component. The system doesn’t just find the component, but it allows you to automatically bring in absolutely every vital part of the component that is mentioned above all within seconds. Think about that one. Automatic connections between the resource into your PCB Data Management system. With a completed Schematic symbol, Footprint, 3D Model, Circuit Simulations, all Component Parameters, Sourcing Information and supporting documents.
We will still need to know where to place that component. As we have already seen, the structure of the Data System should be broken down by Category and Family. For our above example, this component would have the category of Integrated Circuit with a Family of Embedded Microprocessors. That is where this information would be stored with any of its supporting information.
If the information is linked from such a source as Octopart. Than why the need to conduct and audit review? It is to confirm that the component is correct and correctly stored where it should be. I have experienced several times where the datasheet was not correct. Especially views of whether it is from the top or the bottom or the pin numbering of a connector.
Also, because of changes on compliance Standards such as IPC. There are periodic reviews and rewrites of how footprints should be done. Recently a change done in IPC-7351-C was the rounding of the Component pads. With changes like these it takes the industry some time to catch up.
With a completed review and the part Lifecycle changed to a “Released” state this is component is ready to be used in Electronic designs.
As mentioned before, “As a pipeline, we can easily define the required inputs, Roles and expected outputs at any given location in our procedure.” And because the details of each component are used throughout the process combining that with specific roles of individuals we can develop a road map for the usage of what information goes where. Not everyone will even be interested in the same information. For example, a mechanical engineer would not particularly be interested in the electronic specifications for a component with the detail of a slew rate on a control line for the buss. Rather he is interested in the mechanical package and size of it.
This may vary considerably based on every company. These may not be single individuals for individual roles. A single person could do a single task or multiple tasks. Probably the best way to look at this is to see it not as a certain person but as an area of responsibility.
Starting with the engineering and design teams, this would consist of maybe an Electronic Engineer, PCB Librarian, PCB Designer and early in the process the Mechanical Engineer. Than as the project progresses further information will be given to purchasing to begin part procurement and to Quality to start maybe any compliance testing requirements.
All this will be overseen by a Project manager which is difficult to determine the exact data he would be interested in; their main concern is with how all this affects the schedule. From the chart below, can see the sort of breakdown of how specific details of that component get permeated and used by each role. There are substantial overlaps, and this is not a hard-fast rule, but it is a good starting point to get a grasp on this concept.
If you took this to its logical conclusion and to be true to the PCB design process, there should have the required steps, the who and what information would be used. Than at given milestones, an evaluation is done by those individual roles to appraise the outputs from a specific stage…. We than have a Design Review… but that is another subject.
Although this would be considered a usage of the information, I purposely kept it separated from that Step-4 because once the PCB design process gets to this point it becomes much more important to not just evaluate but rather to validate the PCB design. Since it is sometime the last time the checks will be done before the data is distributed to be fabrication and Assembled, this is probably the last chance to catch any mistakes. This is also where other PCB data information is produced and outputted to join the party to become a finished PCB design.
At this point, there will be 2 main roles involved they will be the fabrication and the Assembly needing their specific PCB data information.
There is much discussion today regarding the security of proprietary information and the protection of intellectual properties. Once we get this data into a PCB design how do we protect it? One way to do that is to keep separate these 2 roles. The Data that is provided to the Fabrication is not shared with the Assembly facility and vis versa. Furthermore, under no condition ever is the schematic or any other source files ever released.
Time to make some phone calls to our fabrication/assembly facility to determine what exactly they are looking for in the data they receive. As the industry is changing some information that use to be common has been replaced with other data.
For example, the progression of the Gerber data… Not to go into in too much detail, What was standard Gerbers or RS-274-D was obsoleted in 2014 by an Extended Gerber RS-274X that included meta-information. Many fabrication facilities prefer their data in a certain format. Know that format. Not all these files will be required.
Fabrication Data (Shown Specific for Altium Output Job File)
-Fabrication Drawing with its appropriate notes and instructions.
Assembly Data (Shown Specific for Altium Output Job File
Bill of Material
Assembly Drawing with its required Assembly notes and instructions
Each individual part of each component creates these various data packages. Combined with the input of the resources of specific individuals in their roles. An amazing thing happens, what was only an idea or concept materializes into a real object. It still amazes me every time when I am holding a completed PCB from what was only days earlier a mess of colored wires and information.
The design process is not a straight line but rather it’s a circle. A finished PCB needs to be viewed as a further output of the process and the Data. That connects back into the input. With a finished PCB, an appraisal is done to determine what improvements can be done on the data or the process at the beginning of the pipeline. Many of times this is supported by some sort of documentation such as Design for Manufacturing (DFM) Report or a Build Finding Report. It is what directs any changes In this way, the PCB Data and the process is always being improved on.