Thanks for all the help.

But all of these results are with SN63Pb37. How is this different with
Sn96Ag4?

Paul Stolar
Materials Engineer
Houston Technology Center
Baker Atlas
713-625-5376
713-625-4949 (fax)

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guenter Grossmann
Sent: Thursday, October 02, 2003 10:29 AM
To: [log in to unmask]
Subject: Re: [TN] Reliability solder

Paul

Yes we did some work on the item. Let me outline the results as an
extract from several IEEE publications:
- Degradation is strain driven (Coffin-Manson, with an exponent of
approx.2 for GBS)
- Solder joints degrade due to slow cycle fatigue (creep)
- Creep takes place with 2 main deformation mechanisms (Grain boundary
sliding GBS / Dislocation climb DC). GBS=low strain rate, high
temperature; DC= high strain rate, low temperature
- Deformation mechanism influences degradation
- Strain rate is stress dependent
- Strain = deformation divided through solder thickness 
- Experiments show that a joint as soldered consists of large tin
domains with finely dispersed lead. A joint with plastic deformation
shows refinement of the tin phase and growth of the lead phase
- Recristallisation enables GBS ==> if a recristallised zone is formed
all deformation takes place in this zone. ==> Transformation from global
strain to local strain (higher)
- Shear tests show that slip bands of recristallised solder approx. 15um
on each side of the solder layer form during plastic deformation. ==>
further recristallisation in the middle of the solder joint is slowed
down or stopped

> Decreasing the space between lead and pad causes higher strain thus
faster degradation. Because of Coffin Manson exponent 2: 1/2 of
thickness = 1/4 of Number of cycles to failure
> Decreasing the space between lead and pad leads to increasing strain
rates with given deformation rates (temperature ramps in a test)
> Increasing the space between lead and pads runs into kind of a
saturation because of the formation of slip bands where local strain in
the bands becomes dominant to the global strain over the whole thickness
of the solder

> This only applies to the area between lead and pad. The role of the
fillet is another story.

Sorry for the short form. My wive called me, it's time to go home.


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]

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text
in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at:
http://listserv.ipc.org/archives
Please visit IPC web site
http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------