So, here is a million dollar question:
Can we get money to do the research???;-)
Vladimir
----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Wed Jul 16 17:32:04 2008
Subject: Re: [TN] FW: [LF] [TN] SN100 for Reflow Application
Yup, but only on the ones they built for demo's at
exhibitions..................The real boards were on things like the X-Box
360.........................
John Burke
(408) 515 4992
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, July 16, 2008 12:45 PM
To: [log in to unmask]
Subject: Re: [TN] FW: [LF] [TN] SN100 for Reflow Application
Yeah, I hear ya.
I haven't heard of any solder companies going bankrupt lately. All I
ever hear from them is "Umpteen gazillion boards built without a single
failure!"
Uh huh.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Igoshev, Vladimir
Sent: Wednesday, July 16, 2008 2:27 PM
To: [log in to unmask]
Subject: Re: [TN] FW: [LF] [TN] SN100 for Reflow Application
Other very interesting and almost overlooked things to know (data to
have) would be the fracture toughness for fracture nucleation and
propagation, as well as how and where an initial microcrack gets formed
in the first place.
I wish I had funds for it :-)
Vladimir
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, July 16, 2008 1:52 PM
To: [log in to unmask]
Subject: Re: [TN] FW: [LF] [TN] SN100 for Reflow Application
Thank you, Werner.
All is as I expected. The data probably does not exist.
I wholeheartedly endorse your suggestions, that these "families of
stress-strain curves for various T's and strain rates for Sn37Pb, SAC305
and SN100C and their creep rates be determined, at least on a
comparative basis between SAC305 and SN100C".
I agree this would be helpful in understanding the stresses potential
impact on these alloys. Good project for the solder companies to work
on.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Wednesday, July 16, 2008 11:59 AM
To: [log in to unmask]
Subject: Re: [TN] FW: [LF] [TN] SN100 for Reflow Application
Hi Dean,
You asked the following-post-facing with "I am not a metallurgist, and I
am at a loss as to where to find this information."-unfortunately, there
is no easy way to find the information, and some of it may not as yet
exist.
> 1. Does the elimination of such a small amount of silver from the
> alloy contribute to any significant increase in the solder's ductility
> after soldering is completed?
> A: It is not so much the reduction of the Ag-content (which by the way
> on a
general basis leads to reduced creep-fatigue lives under ATC), but the
addition of Ni and Ge that changes the metallurgical structure of the
alloy. While Keith states that SN100C has better ductility than SAC305,
I have not seen any data, and ductility is not as important as is the
modulus of elasticity (stiffness).
>
> 2.Specifically, can you provide data as to exactly what the ductility
> delta is between all three alloys? I would expect a significant
> difference between 63/37 and SN100 or SAC305, due to the percentage of
> lead.
> A: See above.
>
> 3. Also, with the understanding that VPS would probably provide better
> wetting, how would it otherwise affect the ductility of the alloy
> after soldering is completed? The profile used is essentially the
same.
> A: Typically it is the resulting grain structure that determines
> properties,
so it is not whether you use VPS or something else, but the cooling
rate.
However, please note that the grain structure of solders is unstable and
will coarsen over time, temperature and stress-level enhanced.
>
> 4. For a given assembly that has inherently high CTE stresses due to
> design issues as Amol's assembly presumably has, are you saying that
> using SN100 and VPS rather than SAC305 and convection reflow will cure
> his problems?
> A: Cannot be determined a priori.
>
> 5. How do the long-term creep fatigue rates of Sn100 compare with
> SAC305 and SN63Pb37?
> A: I have not seen data as yet.
>
>
> Werner Engelmaier
Future workshops:
Solder Joint Reliability: Parts 1 through 4, July 17/18, Thal,
Switzerland Pb-Free Soldering Processes-Survival, Quality, Reliability,
August 18, Orlando Reliability Issues with Lead-Free Soldering
Processes, September 22, Schaumburg Failure Mode and Root Cause Analyses
Reliability (Fatigue, Brittle Fracture, ENIG), September 22, Schaumburg
Solder Joint Reliability: Parts 1 & 4, Oct. 9, Moscow, Russia Solder
Joint Reliability: Parts 1 & 4, Oct. 22, Tallinn, Estonia
**************
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