One of the more common plot devices of an action adventure movie is where the hero of the story is in mortal jeopardy due to a rusty bolt, a frayed rope, or some rotten wood. Usually Indiana Jones, or whoever the lead character is, will defy the odds and escape from the bridge, ladder, or staircase just before it collapses. That isn’t so true in real life though where we constantly see examples of “a chain is only as strong as its weakest link,” played out every day.
Take for instance a printed circuit board. The board is only going to be as reliable as its weakest point whether that is a component, the board materials, its design, or how it was manufactured. In order to extend the operating life cycle of a PCB, it makes good sense to look for and improve those areas that may cause the board to fail. Here are some ideas that you should consider for critical area analysis of electronic hardware while in design.
PCB Components: the First Critical Area Analysis of Electronic Hardware
The first area of hardware to analyze during PCB design are the components that are going to be used on the board. Although component analysis can happen at any point during the design, it is better to know before you start what the status of the components are that you will be working with. This way you don’t have to go through a redesign later to replace any parts that have been discovered to have problems.
Obviously you can’t inspect the actual physical components during the design, but you can analyze them based on the data that is available to you. This risk assessment will give you the information that you need to determine if the parts will have any potential vulnerabilities. Here are some areas that you should consider:
Performance: Determine if the part will give you the performance you need for its application. In some cases, choosing a part based on a lower cost may result in a board failure when a more expensive alternative would have been the better choice.
Cost: On the other hand, don’t be afraid to look for lower cost solutions too. Although paying too much may not result in a hardware failure, unnecessary costs can railroad a project just as effectively as a hardware failure.
Compliance: Are the parts you are choosing compliant with regulatory requirements? An example of this is making sure to use RoHS compliant parts for products to be sold in the European Union.
ESD: Some components will have a greater risk of damage to electrostatic discharge, and you need to know which parts fall into this category. You will want to make sure that your board and its components will be handled correctly in order to mitigate ESD exposure for any sensitive components.
Counterfeits: To avoid the problem of ending up with substandard or even counterfeit parts being used in the assembly of your board, be sure to work with known and reputable contract manufacturers.
Status: Make sure that the parts that you specify for your design are available, and not listed with a status of OBS (obsolete) or NRND (not recommended for new designs).
Once you start analyzing your components based off of these considerations, you can help mitigate possible component failures on your assembled circuit boards. The next step is to analyze your design for potential circuitry failures.
Part provider search tools in schematic capture systems can give you a lot of component data
Circuit Analysis Before You Layout the Circuit Board
Circuit simulation has become a standard part of the PCB design process, but even so it should still be considered part of your overall critical area analysis of your electronic hardware design. Not only will circuit simulation help reduce the amount of prototype builds you will have to do, but it can identify potential circuitry problems that bench testing a prototype may not find.
Circuitry analysis is done with SPICE tools and is usually done within your schematic capture program. The important thing is to make sure that your schematic symbols contain the appropriate SPICE models within them to do this analysis. You can usually build these models yourself, or import them from the component manufacturers.
Not only can you simulate the circuitry on the circuit board that you are designing, but by importing other system boards you can simulate the circuit paths throughout the entire system. This will give you a full analysis of your entire system.
PCB Layout and Analysis
Once the circuit simulations are complete and the schematic has been captured, you will then focus on the physical layout of the board. Here there are many different areas that should be analyzed in order to verify the accuracy of the hardware design:
Calculators: PCB design tools usually have a variety of impedance calculators and board stackup generators that will allow you to configure the board layers correctly for your needs. One of the more common hardware failures is excessive electromagnetic interference due to incorrect board layer configurations.
Design rules: Another common problem is manufacturing errors due to incorrect spacing between components and metal on the board. By taking the time to set up your design rules according to the design for manufacturing (DFM) rules of your manufacturer before you start, you will avoid a lot of manufacturing headaches further down the line.
3D Checking: PCB design tools with 3D capabilities will give you the ability to view and check your component placement to each other, and other mechanical hardware in the design. This analysis will save you from a lot of hardware failures due to incorrect part placements. Even if the placement appears to be correct on the board, the hardware may still experience a failure simply because there wasn’t enough room allowed in the design for a human hand to plug a connector in.
Integrity tools: These design features will allow you to verify that the board will operate how you design it. Signal and power integrity tools will tell you if lines are too long, too short, or if there isn’t the correct amount of power coverage in one area of the board.
These tools and features will give you a lot of help, the important thing is to use them.
The 3D tools in PCB design CAD systems will show you potential spacing conflicts
PCB Hardware Analysis Using Your Design Tools
Starting with your components, work through the list of components that you are using and scrub the bill of materials (BOM). The more advanced PCB design CAD systems also offer online part searching capabilities that will supply you with complete data on the parts that you are using. In some cases, those systems will allow you to select a component directly from a list of vendor parts, and place it on your schematic as it downloads symbol, footprint, SPICE, and STEP model information into your database.
Use the circuit simulation tools in your design system to fine tune the circuitry before you complete the design. You can save yourself a lot of prototype costs as well as reduce the possibility of field failures by verifying the circuitry during design. In the same way, use the different calculators and signal & power integrity tools in your design system to verify the layout as you are working with it.
The PCB design system that you need for this high level of critical area analysis of your electronic hardware design is already available for you today. Allegro PCB Designer has the different tools and features that we’ve discussed here, and is ready for you to start working with it to analyze your hardware while you design it.
If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.