Hi Al,
How to you relate strain measured on the package to the strain in the solder joints? What do you mean be "saturated state cycle"?

 The strain range is only a adequate measure under some circumstances, but not all—in others you also need the stress range.
I suggest you follow the procedures in IPC-D-279.
Werner


 

-----Original Message-----
From: al shirazi <[log in to unmask]>
To: [log in to unmask]
Sent: Fri, Jun 19, 2009 11:38 am
Subject: [TN]










Dear TechNeters,

I am measuring strain of a corner joint of a lead-free Lidless FC-PBGA 
package.For the purpose of looking into the fatigue life of the joints under 
thermal cycling (ATC profile).

Is recording strain for one cycle after cycling the package for some cycles is 
good enough to be referred as the saturated state cycle?After how many cycles 
maybe for this type of the  package?Any previous experience?

I appreciate your inputs from either experimental point of view or modeling,
Thanks
Al


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