PCB Design to Ensure Mechanical Reliability

December 10, 2019 Cadence PCB Solutions

Man with a broken down car

Lack of mechanical reliability

 

It’s true, life is full of ups and downs. Maybe the trick is to keep your feet on the ground during the highs and stay on your feet during the lows. Undoubtedly, one of the lows is when your vehicle breaks down and leaves you stranded on the side of the road. There are a plethora of reasons why this situation could happen; however, it seems to be more of a downer when the cause is a mechanical anomaly, as opposed to a more common issue like a blown tire.

The lack of mechanical reliability can strike almost any mechanism or structure. This includes electronic systems that contain a PCB. Depending upon the system, the mechanical failure of a circuit board can result in loss of time, money or even life. Fortunately, the probability of these types of failures can be significantly reduced with a good plan, design, manufacturing process and effective stress testing. Let’s see how to create a design that will facilitate the building of PCBs that have good mechanical reliability.  

What is PCB Mechanical Reliability? 

The first step in devising a good plan for PCB mechanical reliability is to qualify our objective, which is as follows:

PCB mechanical reliability may be defined as the degree of certainty or probability that a circuit board will not suffer a structural failure over its expected operational lifetime.

The definition above assumes that the board will not be subjected to internal or external forces; such as stresses, strains or temperatures that are outside of the tolerance ranges for which it was designed and built. This leads to the next step, which is the determination of the board’s reliability requirements. 

How to Determine Your Board’s Reliability Requirements

Now, that we have qualified what PCB mechanical reliability is we need to quantify it. This means that specific criteria must be established which we can use to set up the manufacturing process. 

 

PCB development standards

IPC Standards for PCB Design, Manufacturing and Testing

 

In order to do this, we must be able to answer the following questions:

 

  • What are the regulatory requirements for your board’s operation?

The minimum mechanical reliability requirements for your board are to meet all applicable regulatory standards. Therefore, you should be aware of how your IPC classification impacts the manufacturing of your design.

  • Will the board undergo vibration?

If your board will be installed as part of an automotive, industrial or aerospace system it is likely to be subjected to vibration, which can have immediate negative effects on the mechanical structure of your PCB. 

  • Will the board be in continuous or intermittent motion?

A single motion may not be felt immediately; however, continuous or intermittent

movement may result in mechanical breakdown or failure.

  • What is the temperature range of the environment where the board will be installed? 

Another significant threat to mechanical integrity is temperature variation or excessive heat or cold. 

  • What are the ranges of voltage and current that will be present during normal operation?

Excessive voltages and currents can cause arcs and shorts that if severe enough causes board material damage.

  • What is the operational lifecycle for the PCB?

No board is expected to last forever; however, it should be designed to operate reliably for its projected lifetime in its nominal environment. 

 

Once these metrics are determined, they must be incorporated into your design to ensure that PCB mechanical reliability.

Designing Your Board to Meet Its Mechanical Reliability Requirements

Designing your board to ensure that it meets or exceeds mechanical reliability requirements and objectives extends into virtually every stage of the design. And your ability to achieve the best design, effectively and easily depends upon what PCB design tool you employ. 

 

PCB design workflow

OrCAD PCB Editor design workflow

 

As shown in the figure above, the OrCAD PCB Editor is comprehensive and provides easy access to all pertinent design criteria. This is but one of the capabilities that are standard as part of Cadence’s PCB Design and Analysis package OrCAD. Additional advanced functionalities; such as real-time DFM checks, 3-D visual integration and new product integration (NPI) make front-to-back design integration faster and simpler. 

If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts

About the Author

Cadence PCB solutions is a complete front to back design tool to enable fast and efficient product creation. Cadence enables users accurately shorten design cycles to hand off to manufacturing through modern, IPC-2581 industry standard.

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