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Subject:	Re: Antw: Re: [LF] Lead-Free Acceleration Factor
From:	Jack Sherman <[log in to unmask]>
Reply To:	[log in to unmask]
Date:	Mon, 10 Jan 2005 09:00:22 -0800
Content-Type:	text/plain
Parts/Attachments:	text/plain (55 lines)

Guenter,

When my lab at Motorola Schaumburg was changed into a condominium, I asked for and received permission to move the cross section and polishing equipment to my personal lab off site.

Personally sensitive to reduction in available resource constraints, If it is worth considering, I will be happy to cross section some of your product without cost to you if you send it to me. Tell me what procedure you want followed, blade speed, location and angle of cut, etc. I have two slow speed Buehler saws and two variable speed polishing platens and lots of potting and polishing materials - - 0.05 micron and up. I use the cold cure Buehler potting materials. I can remove the items from the test penels or you can send me the potted samples. I will not disclose anything I see to anyone else and will not archive photos.

Regards
Jack

Jack Sherman
1395 Highland Blvd
Hoffman Estates IL 60195

Guenter Grossmann <[log in to unmask]> 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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