According to who?

To be honest, I do not know who. But that is the spec, so I don't ask those questions.

 

To be honest, I do not know who. But that is the spec, so I don't ask those questions.

Use your common sense. How many pieces of military equipment do you know of that are still being used after 100 years?

 

Use your common sense. How many pieces of military equipment do you know of that are still being used after 100 years?

I think your are missing the point. The system is not actually going to be used in 100 years, the "one failure in x amount of time" is no more than a measurement of a systems reliability. As time (x) increases the system reliability increases.

And just for laughs the M2 Browning is still in service after 103 years and will probably be used to conquer other galaxies in another 100 years.

 

I think your are missing the point. The system is not actually going to be used in 100 years, the "one failure in x amount of time" is no more than a measurement of a systems reliability. As time (x) increases the system reliability increases.

So how's that working out with Starliner?

 

Then you start with the box making sure it meets mil spec for waterproof integrity to a specified depth and once the guts are in the box you do mil spec shock and vibration testing and any other testing the contract calls out. I have no idea what the product is and really matters not to me. Your board and any / all components must be mil spec. For example you would not use a SN7400 IC on your board, you would use a SN5400 (standard versus mil spec), the latter is a mil spec version of the same chip.

Many Military Standards have been replaced over the years where ISO and AMS specifications are called out. Really depends on the product which specs may or may not apply. Often if a contract is involved the contract will spell out what specifications need to be met. Again, it all depends on the product. Whoever is making the product should know what specifications the product must meet and any testing methods and procedures for final acceptance of the product. There is much more to it than opening a widget factory.

I generally start with a theme tablet and a pencil with a large eraser. Oh yes, you may want to start with IPC-A-610E class 3 standards as an intro to circuit boards.

Ron

Good points, I have started going through and checking to make sure all components meet AEC-Q200 standards and our boards are class 3 compliant. What I am most worried about is breaking solder joints or critical connectors being interrupted during extreme shock or vibration.

 

That was on some things that had internal crypovarables.

The systems I am working on aren't handling any sensitive information. It is mostly physical durability that I have to be concerned with. But thank you for sharing this!

 

Good points, I have started going through and checking to make sure all components meet AEC-Q200 standards and our boards are class 3 compliant. What I am most worried about is breaking solder joints or critical connectors being interrupted during extreme shock or vibration.

Best I can tell you is when a board is made and soldering done the board should run through an inspection process. Solder joints are inspected, usually under magnification. The board may even go through a board test checking functionality.

Ron

 

Nsaspook;
You have considerable experience in the intelligence community.
By any chance were you able to visit Berlin’s Teufelsberg while it still was operational?

I visited the ruined compound in 2019. An awesome place it must have been.

 

In our pcb shop we had IPC certified inspectors and trainers. Here is the table of contents for their big book, IPC-610. The specs for the MIL projects we did that had PC boards referenced this standard.

https://www.ipc.org/TOC/IPC-A-610J_TOC.pdf

https://www.ipc.org/ipc-610-acceptability-electronics-assemblies-endorsement-program

https://www.ipc.org

ak

 

If I put a PCB in a box, throw it into salt water, and set off a bomb next to it, what are some not-obvious ways I can modify the PCB/components to protect it from the shock and elements? It needs to operate flawlessly under these conditions with no faults in 114 years.

This is the maximum acceptable rate of failure. One hiccup in 114 years.

A failure rate is an estimate of the probability of failure. While a MTBF of 114 years seems like overkill if you field 114 copies of this unit you can expect one to fail every year.

 

A failure rate is an estimate of the probability of failure. While a MTBF of 114 years seems like overkill if you field 114 copies of this unit you can expect one to fail every year.

No, you can't. First, that would be an average rate of 1 failure every 57 years. Second, for example, if all 114 units last 114 years and then they all fail, that is an average time-to-fail of 114 years. IIRC, MTTF is not dependent on sample size.

OTOH, I get the point you are trying to make. A variation of that theme was put forth by Wernher von Braun, talking about super-rush, crisis-crisis projects:

"Crash programs fail because they are based on theory that, with nine women pregnant, you can get a baby in a month."

ak