Guenter,

How sad!  Getting the "plug pulled" half way through. I suppose the 
powers that be
figure it is cheaper to find the problems in the field. Well that gives 
Werner some job security!

David A. Douthit
Manager
LoCan LLC

Guenter Grossmann wrote:

>Pascal, David
>
>Well I'm glad someone looked at my article about the concerns of accelerating tests of lead free solder (patting my shoulder). 
>Due to the slower creep rate of lead free solder compared to tin lead and the strong dependency of the temperature on the creep rate dwell times will have to become longer if lead free solder is to be tested. Especially  below 0°C lead free solder creeps very slow. The longer I work the more I am afraid that there is not much about accelerating thermal cycles. Another point to be mentioned is a fact I discussed with Jean Paul Clech lately: We have to expect that the slopes of the Nf-dT lines in a Coffin Manson graph are not the same for SnPb and for lead free solder. This means, that there must be a point where the lines cross each other. It could well be, that tests run with large strain amplitudes might indicate that one solder has a better creep fatigue resistance but a test with small amplitudes (or the application) will show the opposite. 
>Right now we run a slow thermal cycling test -20/120°C, ramps of 2°C per minute and dwell times of 20 min at 120°C and 40 min at -20°C. End of January 4000 cycles will be done. Additionally our Phd student should be finished with his work about deformation behaviour of SnAgCu by the end of this year. This year we planed slow tests with small amplitudes. Seems all well so far, except that we had a cut of founding which left me all alone without a cent left to pay for the analysis of the specimen. I am running around right now to organise money to pay at least for my salary. I don't know if I will make it to the point where I can afford  a person again working in my lab doing the microsections. 
>However, whenever we publish new results they will be posted on our web site.
>
>Best regards
>
>Guenter
>
>
>
>EMPA
>Swiss Federal Laboratories  for Materials Testing and Research
>Centre for Reliability
>Guenter Grossmann,  Senior Engineer
>
>8600 Duebendorf
>Switzerland
>
>Phone: xx41 1 823 4279
>Fax :     xx41 1 823 4054
>mail:     [log in to unmask]
>
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