sowohl als ein Municum

Inge

----- Original Message ----- 
From: "Werner Engelmaier /*" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, March 31, 2009 3:46 PM
Subject: Re: [TN] {Spam?} Re: [TN] solder fatigue predictions for highly 
asymmetrical duty cycles


> Inge,
> Alas, Ich bin ein Unikum.
>
> Werner
>
>
>
>
>
>
>
> -----Original Message-----
> From: Hernefjord Ingemar <[log in to unmask]>
> To: TechNet E-Mail Forum <[log in to unmask]>; [log in to unmask] 
> <[log in to unmask]>
> Sent: Tue, 31 Mar 2009 3:38 am
> Subject: RE: {Spam?} Re: [TN] solder fatigue predictions for highly 
> asymmetrical duty cycles
>
>
>
>
>
>
>
>
>
>
> ...the tricky part is getting all the necessary info, AND getting correct 
> info.
>
> You see what I mean? Try to solve this equation: x+y=
> nothing after the equals-sign, not easy to do any calculation.
>
> has nothing to do with age, rather lack of knowhow. That's why we need 
> many
> werners..
>
> Inge
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
> Sent: tisdag 31 mars 2009 02:01
> To: [log in to unmask]
> Subject: {Spam?} Re: [TN] solder fatigue predictions for highly 
> asymmetrical
> duty cycles
>
> Hi Inge,
> You are going super-conservative in your old age. Heck, I have had 
> accelerated
> tests with mean cyclic lives of 100 cycles and others with no failures in
> 100,000 cycle---It all depends.
> If you understand the load drivers and the connections to cyclic life, you 
> can
> execute a proper Design-for-Reliability in almost all cases; the tricky 
> part is
> getting all the necessary info, AND getting correct info.
>
> Werner
>
>
>
>
>
>
>
> -----Original Message-----
> From: Inge <[log in to unmask]>
> To: [log in to unmask]
> Sent: Mon, 30 Mar 2009 6:28 pm
> Subject: Re: [TN] solder fatigue predictions for highly asymmetrical duty 
> cycles
>
>
>
>
>
>
>
>
>
> not an answer, but some reflections....?
> ?
>
> I'm not a guru, more of a practical gnu. We have some math specialists who 
> have
> produced models and calculations that make a normal reader exhausted to go 
> from
> page 1 to page 200. After going through some reports like that, you feel 
> rather
> disoriented. So, in order to know about the failure modes and six sigma, 
> Time to
> Failure and such parameters, we decided to go the hands-on way. We 
> 'simply'
> produced a lot of cloned boards with a substantial lot of components on, 
> and
> started temp cycling with various symmetries and limits. Believe it or 
> not, we
> have passed 10,000 cycles in some cases. The result will not be known 
> until the
> end of this year. This method is not very comfortable either, making all 
> these
> hundreds of microscope inspections and measure daisy chains and other 
> stuff.
> Because our customer wants this way, we simply do it. Personally, I prefer
> neither of the ways, but more of a cautious and well performed design. 
> Follow
> the derating rules, don't buy components from unknown manufacturers,  hold 
> back
> when the design engineers excess in very large or very odd boards,  keep 
> to a
> board producer you know, don't mix extremly hot components with mW 
> components
> and a lot more of goodies .  Sounds like stopping the development of new
> technology, but after reading Toyota's LEAN thinking, it seems as making 
> many
> small development steps are safer, than to make a brand new super design. 
> In
> earlier days, we had time to make prototypes, take our time and make a 
> small
> pre-series, then introduce improvements, longlife test and slowly start 
> series
> production.
> Now we go directly from CAD engineering to production....?
>
> says an old dog?
> ?
>
> Inge?
> ?
>
>
> ----- Original Message -----
> From: "Nieznanski, John A - SSD" <[log in to unmask]>?
>
> To: <[log in to unmask]>?
>
> Sent: Monday, March 30, 2009 10:05 PM?
>
> Subject: [TN] solder fatigue predictions for highly asymmetrical duty 
> cycles?
> ?
>
>
> Hello Tech-Net Gurus,?
> ?
>
> The solder fatigue parameters called out in IPC-D-279, IPC-SM-785 and
> IPC-9701 all assume symmetrical (i.e. 50%) duty cycles and temperature 
> swings.
> This raises the question as to how far these calculations can be pushed to
> predict solder fatigue in low duty cycle, variable duty cycle or high duty 
> cycle
> applications.?
> ?
>
> In particular, Tsj ( = mean cyclic solder joint temperature), and tD ( =
> half-cycle dwell time in minutes) are both used and are directly affected 
> by
> duty cycle. It is simple enough to recalculate these values based on
> asymmetrical duty cycles, but how do we know that the predicted solder 
> fatigue
> results are still valid? If we know, do we know what assumptions are 
> required to
> make the results valid? This seems like a fairly common situation. Has 
> anyone
> correlated measured results to predictions in this regard??
> ?
>
> Specifically, there are numerous caveats in the specs including for 
> example,
> high-frequency (e.g, vibration) conditions where tD < 1 second, but none 
> of
> these caveats apply here.?
> ?
>
> For example, with a power on dwell time of 6 minutes (system reaches 
> thermal
> equilibrium in < 1 minute) and a power off dwell time of 54 minutes (10% 
> duty
> cycle), I assume I can simply use tD = 6 minute dwells and Tsj = average 
> solder
> joint temperature over 60 minute cycle. Do you agree with this approach??
> ?
>
> Another potential case of interest is if the duty cycle is reduced to 
> something
> less than 1 minute (but more than 1 second; not a vibration situation), 
> such
> that the stabilized operating temperature is not reached.
> Can any valid fatigue calculations be performed in these cases if I can
> determine a valid Tsj for a 1 minute tD??
> ?
>
> Thanks in advance for your insights and assistance.?
> ?
>
> Best regards,?
> ?
>
> John N.?
> ?
>
>
> ________________________________?
>
> This e-mail and any files transmitted with it may be proprietary and are
> intended solely for the use of the individual or entity to whom they are
> addressed. If you have received this e-mail in error please notify the 
> sender.?
>
> Please note that any views or opinions presented in this e-mail are solely 
> those
> of the author and do not necessarily represent those of ITT Corporation. 
> The
> recipient should check this e-mail and any attachments for the presence of
> viruses. ITT accepts no liability for any damage caused by any virus 
> transmitted
> by this e-mail.?
> ?
>
> ---------------------------------------------------?
>
> Technet Mail List provided as a service by IPC using LISTSERV 15.0?
>
> To unsubscribe, send a message to [log in to unmask] with following text in?
>
> the BODY (NOT the subject field): SIGNOFF Technet?
>
> To temporarily halt or (re-start) delivery of Technet send e-mail to
> [log in to unmask]: SET Technet NOMAIL or (MAIL)?
>
> To receive ONE mailing per day of all the posts: send e-mail to
> [log in to unmask]: SET Technet Digest?
>
> Search the archives of previous posts at: 
> http://listserv.ipc.org/archives?
>
> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
> for additional information, or contact Keach Sasamori at [log in to unmask] or
> 847-615-7100 ext.2815?
>
> ----------------------------------------------------- ?
>
> ---------------------------------------------------?
>
> Technet Mail List provided as a service by IPC using LISTSERV 15.0?
>
> To unsubscribe, send a message to [log in to unmask] with following text in?
>
> the BODY (NOT the subject field): SIGNOFF Technet?
>
> To temporarily halt or (re-start) delivery of Technet send e-mail to
> [log in to unmask]: SET Technet NOMAIL or (MAIL)?
>
> To receive ONE mailing per day of all the posts: send e-mail to
> [log in to unmask]: SET Technet Digest?
>
> Search the archives of previous posts at: 
> http://listserv.ipc.org/archives?
>
> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 
> for
> additional information, or contact Keach Sasamori at [log in to unmask] or
> 847-615-7100 ext.2815?
>
> -----------------------------------------------------?
>
>
>
>
>
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 15.0 To
> unsubscribe, send a message to [log in to unmask] with following text in the 
> BODY
> (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start)
> delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or
> (MAIL) To receive ONE mailing per day of all the posts: send e-mail to
> [log in to unmask]: SET Technet Digest Search the archives of previous posts 
> at:
> http://listserv.ipc.org/archives Please visit IPC web site 
> http://www.ipc.org/contentpage.asp?Pageid=4.3.16
> for additional information, or contact Keach Sasamori at [log in to unmask] or
> 847-615-7100 ext.2815
> -----------------------------------------------------
>
>
>
>
>
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 15.0
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt or (re-start) delivery of Technet send e-mail to 
> [log in to unmask]: SET Technet NOMAIL or (MAIL)
> To receive ONE mailing per day of all the posts: send e-mail to 
> [log in to unmask]: SET Technet Digest
> Search the archives of previous posts at: http://listserv.ipc.org/archives
> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 
> for additional information, or contact Keach Sasamori at [log in to unmask] or 
> 847-615-7100 ext.2815
> ----------------------------------------------------- 

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------