ALTA Life-Stress Relationship

[swalex]

Is it possible to use Life-Stress relationship as below in ALTA?

TTF(x)= A exp (-Bx)

or

TTF(x) = A exp (B/x)

-Swalex

[David]

Hi Swalex,

Basically, you are referring to the Arrhenius life-stress relationship, correct? Yes, this model is included in ALTA 7. Additional information on the Arrhenius model can be found at http://www.weibull.com/AccelTestWeb/arrhenius_relationship_chap_.htm. The equation that is used in ALTA is:

L(V) = C*exp(B/V)

where:

V = stress
B and C = parameters to be estimated

An overview of ALTA's features can be found at http://www.reliasoft.com/alta/features.htm. In addition, a demo version of ALTA can be dowloaded from our Download Store at http://www.reliasoft.info/download/product.php?productid=9&cat=6&page=1.

I hope this helps.

[swalex]

Thanks David for your reply.
How about below relationship?

TTF(x)= A exp (-Bx)

I am testing TDDB test on insulator layer in semiconductor and was told to use above equaition to calculate lifetime of the layer.

Thanks,
-Swalex

[David]

Yes, this equation can also be used via the General Log-Linear (GLL) model. Additional information on the GLL model can be found at http://www.weibull.com/AccelTestWeb/general_log_linear_model.htm. The GLL model allows you to specify a stress tranformation for each stress. In your case, you would not apply a transformation. So, for the GLL model with a single stress:

L(V) = exp(Alpha0 + Alpha1*V)
= exp(Alpha0)*exp(Alpha1*V)

Therefore, to get your equation:

Set exp(Alpha0) = A and Alpha1 = -B

You end up with the following:

L(V) = A*exp(-B*V)

Keep in mind that ALTA will return the parameters Alpha0 and Alpha1 in this scenario. The GLL model is very flexible and allows for the analysis of data with up to 8 stresses. In addition, it can be reduced to the Arrhenius model if the proper stress transformation is used. The available stress transformations are presented in the link above.

I hope this helps.

[swalex]

David,
Thanks a lot for your help!
-Swalex