Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Accelerated testing to Service life conversion

Brad R.

#17111

Accelerated testing to Service life conversion | 6 August, 2001

I am having some SMT assemblies undergoing thermal shock testing per MIL-STD-883, Method 1011, Test Condition B. I was wondering if anyone has a chart, equation, article, etc. that will give me an idea of the service life of the assembly after it survives X number of cycles. I have seen a table from the IPC-SM-785 standard that gives this information for temperature cycling but I haven't seen anything similar for the MIL standard. Does anyone have any suggestions?

Thanks, Brad

This message was posted Add this forum to your site! Click to learn more. the Electronics Forum @

reply »

#17133

Accelerated testing to Service life conversion | 7 August, 2001

First, we know that MIL types are wont to use charts like that. Give �em Weibull distribution tables and then they�ll be happy, happy. A good book is Nelson �Accelerated Testing: Statistical Models �� Wiley

Second, we don�t use that very nice stuff coz it makes our heads hurt. Here�s two angles that you can play with and see how they compare to other things you find:

1 From G Grossman over at Swiss Federal Institute for Materials Testing and Research � A rough estimate of the lifetime in a real time environment by: Nfr=Nft*(dTt/dTr)exp(1.7) ... where: Nfr = Number of cycles to failure reality Nft = Number of cycles to failure test dTr = Temperature swing reality dTt = Temperature swing test

2 From Process Sciences [512-259-7070], Arrhenius Product Life Calculator/Estimator: Tm2=Tm1*(10^(Ea/2.303R*(Tp2-Tp1)/(Tp1*Tp2)) � where: Tm1 = Component's original life span in days Tp1 = Component's original operating temperature in Celsius (�C must be less than or equal to 95�C) Tp2 = Component's elevated test temperature in Celsius (�C must be less than or equal to 95�C) R = Universal Gas Constant 8.314 J/mol*K Ea = Activation Energy for corrosive reaction in Sn/Pb/Cu substrates 50,000 J/mol Tm2 = Component's calculated life span at the elevated temperature

Finally, we are aware of IPC-9701 "Performance Test Methods and Qualification Requirements for Surface Mount Solder Attachments", but don�t have a clue of what�s in it. [If you get it, but two and send us one.]

reply »

Boundary Scan

JTAG Live PCB Debug Software