Military Standard 217F Questions

[qualitygoddess]

Couple of questions for the experts, since this is out of my league. We want to do a reliability calculation to get MTBF for a populated circuit board. It's a device that runs a computer touch screen. Is Mil std 217F the right standard?

When doing the calculation, can we use either the Part Stress Analysis or the Part Count calculation? I read the difference in the standard's introductory pages, but can someone explain the difference in practical terms?

Thank you!

[Al Rosen]

Originally Posted by qualitygoddess

Couple of questions for the experts, since this is out of my league. We want to do a reliability calculation to get MTBF for a populated circuit board. It's a device that runs a computer touch screen. Is Mil std 217F the right standard?

When doing the calculation, can we use either the Part Stress Analysis or the Part Count calculation? I read the difference in the standard's introductory pages, but can someone explain the difference in practical terms?

Thank you!

Let me start by stating I'm not an expert, but my understanding is that the parts count method is used early in the design to determine whether your design is in the ball park. The stress analysis is performed later in the design process when you know the operating (voltage, current, power) and environmental (temperature, etc) parameters.

If you are looking for an MTBF of 50,000 hrs and you calculate an MTBF of 10,000 hrs using the parts count, you probably should reconsider your design. Remember also, that this is a prediction used to compare designs and you will not necessarily see the same numbers in actual use.

Reliability Prediction Analysis