Designing accelerated life test

[project]

Iam planning an experiment to estimate life of a PCB module using accelerated life testing.The accelerating variable is temperature.
I need to know how to determine the temperature range (Tmin,Tmax)for this experiment analytically, especially the temperature Tmax such that failure mechanisms/modes of the module dont change. Operating temperature max is 70 degrees.

[Highkeas]

I'm surprised that you did not receive a response to your query yet.

All I can say is that I use an Arrhenius based equation to determine test time (on chemical-mechanical-electrical devices).

HL = HT x 3^((t1 - t2)/11.1)

where:
HL = service life in hours
HT = test time duration in hours
t1 = test temperature in degrees C
t2 = in-service median storage temp in deg C
3.0 = reaction rate factor.

I select t1 based either on the physical properties of its components or adding 11 deg C to the max service temp. I use this method to verify customer service life requirements.

[jfkey]

How can I follow your calculation method?Could you please suggest any book, article etc to calculate service life?

[Highkeas]

ASTM G172 - 03(2010) Standard Guide for Statistical Analysis of Accelerated Service Life Data

AIAA-S-113-2005 (source for above equation)

Try googling Arrhenius equation for service life

[johnmcrin]

I am currently running an Accelerated Life test of a part and using temperature cycling as a stress. 3 upper levels of stress are being used 800 F, 650F, 500F and lower level is 250F. The current design has the swing between 200F to 115F but I just found out that the design stress level is going to vary with a new design and the lower limit of 115F does not hold good in the new design which runs between 170F to 50F. My original plan was to compute Life Vs stress as a function of Delta T, but since the lower limit does not hold good, I tried computing Mean Temp and used Delta T to calculate life at design stress. The life prediction using Mean Temp varies using Delta T quite significantly. To the order magnitude of 10^3. Can somebody provide any ideas to model this accurately in ALTA.

Regards
John