Life calculations for circuit boards

[siliconsage]

Hi Guys,

I'm working on a new design for a customer and I've been asked to predict the lifetime of the PCB under certain conditions.

I've used Milspec 217 before but I know it is very pessimistic and doesn't do the design any favours. I also know that using the calc, it suggest what components I should look at when seeking to improve the design.

I was just wondering what methods the rest of you are using ATM, and if there are any online references that are free.

Thanks

 

[IRstuff]

There are several other approaches; Bellcore is probably the most common alternative.

However, a PCB has other life killers beyond just the components. Solder joint life requires knowing how the board flexes under actual conditions. Physics of failure models have been developed to account for that type of phenomenon.

TTFN

FAQ731-376

 

[siliconsage]

Hi IRstuff,
Any idea where I can get a copy of the Bellcore spec from?
I've tried google, but it isn't showing a place to download it.

Regards,
Ad

 

[mcgyvr]

Bellcore is known as telcordia now. (and they all typically cost alot for each spec)
Search for SR-332
and ARPP Version 10.0 (excel program that uses Sr-332)

and

http://www.relex.com/

 

[uWaveFDL]

Try this program...it's free and easy to customize.

http://home.comcast.net/~pstlarry/MH217F1.htm

 

[siliconsage]

Hi everyone,

Just to point out, I'm already using MILSPEC 217F.
I was after something else to put forward in front of the customer.

ATM the FETs and electrolytic cap are the worst offenders. The capacitors I can mitigate, but the FETs are always an issue no matter what parts I use.

So, if I can find a reliability spec that is "kinder" to the design, I'm all ears.

Thanks,
Ad

 

[IRstuff]

Why are you using 217 if you don't need to? HAve you looked at Telecordia?

If you are having that much of a problem with single transistors, then you need to either reduce the operating temperature or lower the environment.

TTFN

FAQ731-376

 

[uWaveFDL]

Try this one at Freescale.
I haven't used it but it's product specific. Find a similar FET. The data should be more reliable.

MTTF calculator available at

http://www.freescale.com/rf.

Select Tools/Software/Application Software/Calculators to access the MTTF calculators by product