Hi,
I specified pull/peel test in one occasion: the designer plugged the hole from the secondary side with laminate for isolation of the metallic layer (safety). Hence, the only through hole component (which is the power connector, is partially penetrating into the PCB, with no support in the secondary side and no way to inspect the vertical fill. I specified the pull out torque of a press fit connector and it work.
However, I refer to this test as destructive, hence I scrap the tested units. The sample is being taken from all the operators working on this product.
Regards
Ofer Cohen
Manager
Quality Assurance, Reliability and Production Technologies
Seabridge Ltd. - A Siemens Company
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Werner Engelmaier
Sent: Thursday, October 28, 2004 14:59
To: [log in to unmask]
Subject: Re: [TN] Standards that refer to cosurface mount component pull test
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
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