My youngest daughter has quite the independent spirit, and she has always charted her own course in life with a careful balance of larger-than-life self-confidence and thoughtful analysis. Once when she was young she was trying to do something that broke a family rule, and I told her that if she continued down this path that I would ground her. Instead of conceding my authority as her parent and following my instructions, however, she instead responded with, “grounded? For how long?” I was stunned. She was doing a risk assessment by balancing the rewards of breaking the rules against the amount of punishment she would receive – and she was only 10!
That incident definitely wasn’t my first experience with failure mode and effects analysis risk assessment, but it will certainly stand out as one of the more memorable ones. One of the more common applications though is when we use FMEA risk assessments to make informed selections of the electronic components that we use in PCB designs. This is an important step in the design of a printed circuit board and will have a long lasting impact on its operational life. Let me explain further.
What is FMEA Risk Assessment of PCB Components?
There are several different criteria used for defining circuit boards such as the materials they are made from, how well they are designed for their intended purpose, and the quality of their manufacturing. Yet there is one area that is often overlooked; the quality of the components that are used on them. Without components that operate at their expected levels of performance, a printed circuit board will not function as it is expected to. For circuit boards that are used in mission critical applications, this can be a huge problem and is a risk that can’t be tolerated.
Another qualifier of components used on circuit boards is their availability. This is very important for circuit boards that are used in low volume products that are expected to have a long service life. These include military applications, such as ships, submarines, and aerospace as well as industrial equipment and other capital equipment that can be in use for decades. Electronic products like these are designed to be maintained instead of replaced, and it is essential that the necessary circuit board builds be built over the lifetime of the product. Components that are at risk of becoming prematurely obsolete and unavailable will put these future builds at risk and is also something that can’t be tolerated.
For these reasons it is very important that PCB design engineers accurately project the full life cycle of the boards that they are designing by knowing the potential for risk in the components that they are using. This is done by considering all of the possible problems that can happen with PCB components by doing a failure mode and effects analysis risk assessment on them before committing to their use. Here are some of the concerns and risks that PCB design engineers should consider in their analysis when making their component selections:
Performance: Not all component vendors or suppliers are the same, and some will produce or supply components that are of higher quality than others.
Compliance: There are different regulatory requirements that must be followed depending on where your products will be sold. Laws such as the restriction of hazardous substances (RoHS) will affect which components are available for you to use.
Substandard and Counterfeits: Parts that are not compliant, have been restocked after non-use, or are not recommended for use can cause problems when they are distributed as good parts.
Obsolescence: Components that are obsolete or are going obsolete can create future difficulties for procurement if used in new designs.
All of these concerns should be part of the risk assessment that you do on the components that you are planning on using in your designs before you commit to using them.
FMEA risk assessment will help you to select the best PCB components for circuit simulation
Mitigating Risk in the Selected PCB Components
Working with trusted vendors and suppliers for the highest quality components to select from is half the battle. By using these components you should be able to rule out problems with substandard parts and counterfeits. Those parts that do end up getting used however must still be verified to assure their useability. Whether in house or at your manufacturer, the parts you use should be carefully inspected to make sure that you have gotten the correct parts, and that they are correctly packaged and ready for assembly. Inspection like this will help to mitigate further component risk by utilizing some of the following methods:
Inspecting incoming components according to industry standards such as IDA-1010.
First article physical inspection and documentation of all new types of components.
Verification of components according to physical specifications of the data sheets.
Component lead finish evaluation.
Component die verification.
Once the best quality components are verified and ready to be used, there still is another step to go through in order to make sure that failure risks are mitigated. Components must be handled according to specific guidelines by trained personnel to ensure that they are not damaged before they are used on the board. Some of the problems include moisture that can be absorbed during handling, and electrostatic discharge (ESD) contamination that can potentially damage an unprotected part.
Once you have confirmed that the parts are of good quality, have been inspected for correctness, and are being handled according to strict guidelines, you will have greater assurance on the quality of your circuit boards.
Make sure to select good quality and reliable components before you begin circuit simulation
When choosing the proper component, simulation is an invaluable tool for any design engineer. SPICE tools with vast model libraries will provide you with the options to choose the absolute optimal component (based on supplier availability of course) for your design’s needs. However, knowing what the optimal component would be for your design is also in the domain of your SPICE tool’s operations.
Being able to model several different varieties of the same component against each other within the same circuit design or area of a circuit enables you to see the effect directly of using, perhaps, a more heat-resistant component versus one that requires a hair less voltage to operate at peak efficiency.
The Long Term Goal of Your Component Management
FMEA risk assessment means understanding and identifying the problems with component supply management, and mitigating those risks. This will require you to put into practice methods and procedures that will ensure that the parts you use will be of the best quality and available for the full life cycle of the product. These policies will reduce your exposure to the liability of component problems, and help you to build products that will perform the way you intended them to.
For manufacturers and part procurement personnel, this will mean qualifying vendors and suppliers as well as inspecting and validating the parts that are to be used. For PCB design engineers this will mean working with and scrubbing their bill of materials (BOM) before they engage in schematic capture and simulation. By working ahead with the BOM, PCB designers can identify and eliminate counterfeit or non-comforming components. With a scrubbed BOM containing parts approved by procurement, designers can then work towards developing their schematics for simulation.
Once your parts are ready to be used in your design, you will need the best circuit simulation software that you can get. The Cadence family of PCB design tools has one of the most trusted simulation tools on the market today that is used by scores of design engineers just like you. PSpice is fully integrated into the Cadence schematic capture tools and is feature rich with its functionality and capabilities. From there the Cadence suite of design tools will allow you to design all aspects of your printed circuit board including advanced tools to work with and scrub your bill of materials.
If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.