Mary,
One must be mary careful not to inadvertantly remove life from your
product. We have found that the vibration spectrum of the HALT/HASS chamber
does not represent in any way the vibration / shock encountered in the
actual application. What is particularly important is the effect HASS has
on connectors within the module with respect to fretting. HASS can actually
cause very severe fretting (large amounts of energy at high frequencies) in
connectors. Any fretting reduces the life/reliability of the connector.
We have many examples where the module will pass qualification tests of:
Shock Life (500K pulses, 40G, 10ms)
Vibration Life (spectrum from product @ +6dB)
showing no connector fretting. However, HALT test for the same module
results in severe connector fretting wear.
HASS may induce unwanted wear in UUT connectors.
Mark
Mary Lin
<mary2001@ROAD To: [log in to unmask]
FLY.ORG> cc:
Sent by: Subject: Re: [TN] test method to detect solder joint weakness
TechNet
<[log in to unmask]
RG>
04/09/02 04:55
PM
Please respond
to "TechNet
E-Mail
Forum.";
Please respond
to Mary Lin
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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