Yes, nothing new, old stuff. But Universal will start intense
accelerated tests with various board and package configurations in order
to find the optimums. The last report this year is indeed optimistic.
Peter is just now discussing these details with us before the tests
start. I have proposed even superBGAs, but not many are using them. LGAs
are also of interest, but they will neither be included. It's a large
program, Peter will have a very tough year(s) before the program is
ended. I suppose many TN members are involved in Universal's program.
We are soldering LF every day and we have been lucky so far. Until
today, in fact. One BGA won't melt. I performed analysis of the balls
and found that it wasn't LF but something like 63Sn37Pb. Why I say
'like' is because there was a difference between the ball surface and
the bulk. The balls had a peculiar surface structure, composition
approx. 95Sn, while the bulk was more like 63Sn. So, that was a
surprise, and will not be the last one.
Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Mike Buetow
Skickat: den 19 april 2007 20:25
Till: [log in to unmask]
Ämne: Re: [TN] Fragility of Pb-free Solder Joints
That's a 2004 paper they did. It's on the Universal website.
http://uic.com/wcms/WCMS2.nsf/index/Resources_75.html
Mike
Mike Buetow
Editor in Chief
Circuits Assembly
30 Glenburnie Road
Boston, MA 02131 USA
W/mobile: 617-327-4702
The 2007 Directory of EMS Providers: circuitsassembly.com/cms/dems
>>> [log in to unmask] 4/19/2007 2:19 PM >>>
This just came in my email from SMT Net. I have not been able to link
to the
article yet but the title and first paragraph sounds familiar.
Joe
_Fragility of Pb-free Solder Joints_
(http://www.smtnet.com/adsystem/redir.cfm?adid=831)
_Universal Instruments_
(http://www.smtnet.com/company/index.cfm?fuseaction=view_company&company
_id=46383)
Credit/Source: Peter Borgesen, Surface Mount Laboratory, Universal
Instruments; and Donald W. Henderson, IBM Corporation
Recent investigations have revealed that Pb-free solder joints may be
fragile, prone to premature interfacial failure particularly under
shock loading,
as initially formed or tend to become so under moderate thermal aging.
Depending on the solder pad surface finish, different mechanisms are
clearly
involved, but none of the commonly used surface finishes appear to be
consistently
immune to embrittlement processes. This is of obvious concern for
products
facing relatively high operating temperatures for protracted times
and/or
mechanical shock or strong vibrations in service...
************************************** See what's free at
http://www.aol.com.
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