Mary,
As long as your "PC's" are not laptop types then thermal cycling will be enough.
The stress level is very dependent on the temperature range as well as the rate of change and dwell
times.
Remember that even though different materials may have close CTE's they may have widely divergent
rates of temperature change (I. E. metals vs polymers vs ceramics).
David A. Douthit
Manager
LoCan LLC
Mary Lin wrote:
> Thanks for all of your response!
>
> David, you are right, what I am looking for is ALT (accelaerated Life
> Test)correlation with field application. Given our products are PC,meaning end
> user environemt is not complex, is a math equation available if performing
> thermal cycling or vibration to manifest the solder joint failure over the
> warrenty period?
>
> If only for the purpose of detecting solder joint failure, since it takes a
> lot of efforts to make the RS vibration fixture, will thermal cycling as the
> stimuli be efficient enough due to common failure mechanism--low cycle
> fatigue?
>
> Thanks again.
>
> Mary
>
> n Tue, 09 Apr 2002 13:00:18 -0700
> David Douthit <[log in to unmask]> wrote:
> >Mary Lin
> >
> >
> >(1) Whichtest is more efficient, thermal cycling or RS Vibration? Yes!
> > Why do you think it is necessary to choose?
> > They are not capable of being separated if the end use has vibration
> >and temperature changes.
> >
> >(2) how to correlate number of cycles of test (either thermal cycling or
> > vibration) with service time in the field application?
> > That is not the purpose of these tests!! These tests are ;
> > 1. HALT is used to find the "destruction" stress limits of the product.
> > 2. Hass is used to screen the products at stresses below the limits
> >determined by HALT to detect
> > latent defects and/or poor processes
> >
> >These tests are primarily used to lower warranty or infant mortality
> >problems.
> >What you want is sometimes referred to as ALT (Accelerated life-cycle
> >Testing)
> >Creating protocols that can correlate to field exposure levels is very
> >complex and time consuming.
> >
> >Usually there is very little accurate data about the end use conditions
> >available.
> >The test equipment would need to be capable of synergistic combinations of
> >numerous stresses.
> >All in all attempting to determine the long term reliability of products is
> >very problematic.
> >
> >David A. Douthit
> >Manager
> >LoCan LLC
> >
> >
> >
> >
> >Mary Lin wrote:
> >
> >> Hello-
> >>
> >> As we know both thermal cycling test and RS vibration test in HALT (Highly
> >> Accerlated Life Test) are effective in detecting solder joint related
> >> failures.
> >> Right now we are in the process of developing HASS profile, can someone help
> >> me on fllowing questions?
> >>
> >> (1)Which test is more efficient, thermal cycling or RS Vibration?
> >> (2) how to correlate number of cycles of test (either thermal cycling or
> >> vibration) with service time in the field application?
> >>
> >> Thanks for your time.
> >>
> >> Mary
> >> _________________________________________________________________________
> >>
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