Hi 'jyazdanpanah',
There is a good reasons why no 'pull test' standards exist.
First, there cannot be such thing as a real 'lead pull test;' while you are
of course pulling on the lead, what you are doing to the solder joint is
peeling it--the proper reference is a lead peeling test.
Second, the solder joint strength, as determined by a lead peeling test, has
no bearing on the reliability of the solder joint, provided the peeling test
does not reveal inadequate wetting or poor metalization, e.g., 'Black Pad.
Third, in a peeling test you always need to observe the whole peel-load
history for the whole peeling process; with a 1T or larger heel fillet, the largest
load will be at the initial portion of peeling through the heel fillet, with
lower loads subsequently depending on whether or not (or to what extent) side
fillets are present.
Fourth, the fracture surface of the peeled solder joints give typically more
information than do the peel-load histories, because the ONLY really important
finding is whether or not adequate wetting has taken place, i.e. the
separation is mostly in the solder vs. being onterfacial.
Fifth, the reliability in actual use does to a large extent depend on the
heel fillet and the 'bottom flat' wetting; if the foot length is <3W, than also
on the presence of a toe fillet, because short feet 'rock' during thermal
cycling. Side fillets are less important, unless you have wetting problems.
Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com
---------------------------------------------------
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 847-615-7100 ext.2815
-----------------------------------------------------
|
