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Date: | Wed, 16 Nov 2005 18:45:37 -0000 |
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Thanks Werner, THAT was a professional answer! I'll dig in that topic and come back later. FYI we have created a big LF group, all specialists and production people within the whole company. What we recommend is spread to all instances worldwide.
Inge
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: den 16 november 2005 19:36
To: Ingemar Hernefjord (KC/EMW); [log in to unmask]
Subject: Re: [TN] [LF] Reliability prediction of LF soldering
Hi Ingemar,
We have been aware for some time that the lead-content is higher near the IMC layers, because some of the Sn has been used to form the IMCs. However, any Pb-nonuniformity that might otherwise be present in solder joints would have its impact felt [but not directly recognized] in the results of any accelerated testing.
Now if there is a difference between the Pb-uniformity between the short-term ACT samples and the long-term product solder joints, that is a different matter--and I do not know how to currently address it.
We do, however, know of a difference between the short-term ACT samples and the long-term product solder joints. that is the coarseness of the solder grain structure which changes over time with temperature and loads. The difference can be as high as a factor of 2 to 3. that is why IPC-SM 785 and IPC-9701 recommend artificially aging [meaning grain coarsening] solder joints prior to ACT.
Werner
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