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Subject:
From:
"Igoshev, Vladimir" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Igoshev, Vladimir
Date:
Thu, 11 Dec 2008 18:59:28 -0500
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Hi Werner,

A sibgle crack is a result of a non-uniform loading but that is what happens in solder joints almost all the time and in the joints on SMD pads in particular.



With all due respect, I don't think that once a ckack is created its kinetic can be described only based on the fatigue-damsge accumulated in the bulk of solder.



Regards,



Vladimir





________________________________



From: Werner engelmaier 

To: Igoshev, Vladimir; [log in to unmask] 

Sent: Thu Dec 11 18:26:54 2008

Subject: Re: [TN] Xbox360 BGAs 





Hi Vladimir,

A single crack signifies a non-uniform loading condition/stress concentration geometry. Even than, "accumulation of creep-fatigue damage" is still the life-time controlling process.



Werner







-----Original Message-----

From: Igoshev, Vladimir <[log in to unmask]>

To: TechNet E-Mail Forum <[log in to unmask]>; Werner engelmaier <[log in to unmask]>

Sent: Thu, 11 Dec 2008 9:42 am

Subject: RE: [TN] Xbox360 BGAs





Hi Werner,







 







That is a completely different story J and "Yes" it is one possible



scenario where the life time prediction can be made based on



"accumulation of creep-fatigue damage". In other words, to predict the



life time one would have to know the rate of accumulation of total



damage (voids, as I wouldn't call them cracks in that particular case)



distributed throughout the joints.







 







However, in many-many case a single crack starts growing in a joint,



finally causing its failure. That is the scenario I was referring to in



my original e-mail and "accumulation of creep-fatigue damage" my not be



the life-time controlling process.







 







Regards,







 







Vladimir











-----Original Message-----



From: TechNet [mailto:[log in to unmask] <mailto:[log in to unmask]> ] On Behalf Of Werner engelmaier



Sent: Wednesday, December 10, 2008 10:05 PM



To: [log in to unmask]



Subject: Re: [TN] Xbox360 BGAs







 











 Sorry,



that's what comes from doing things waiting for an airplane- should have



been "...micro-voiding at grain boundary intersections,..."







Werner











 







-----Original Message-----



From: Igoshev, Vladimir <[log in to unmask]>



To: [log in to unmask]



Sent: Wed, 10 Dec 2008 4:26 pm



Subject: Re: [TN] Xbox360 BGAs











































Hi Werner,







 







I got used to calling it grain boundary triple junction (it's just



probably different terminologies). However, since I know what you meant



I'm confused with the whole sentence: "In any case, grain coarsening



comes first, micro-voiding and grain























boundary intersections next...", triple joints are there to begin with.







 







Regards,







 







Vladimir







 







________________________________







From: Werner engelmaier [mailto:[log in to unmask] <mailto:[log in to unmask]> ] 



Sent: Wednesday, December 10, 2008 4:21 PM



To: Igoshev, Vladimir; [log in to unmask]



Subject: Re: [TN] Xbox360 BGAs







 







 







Hi Vladimir,







"Grain boundary intersections" occur where 3 or more grain boundaries



come together. 



















Purely metallurgically speaking, things get more messy on a scale



smaller than grain size, but 



















in terms of SJ rel consideration on the grain-size level is sufficient.










































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