Possible low copper foil peel strengths.  PTFE and Ceramic HydroCarbons
have fairly low peel strengths, but are less affected by temperature
excursion like FR4 and other thermo-setting resins.  Your PCB supplier
should have copper foil peel strength numbers from monthly testing and a
drop off would be noticeable.  Construction also has an impact on bond
strength as well as copper foil type. 

Jeffrey Bush
Director, Quality Assurance and Technical Support
VERMONT CIRCUITS INCORPORATED 
           76 Technology Drive - POB 1890 
              Brattleboro, Vermont 05302
                Voice - 802.257.4571 ext 37 
                    Fax - 802.257.0011
                       <http://www.vtcircuits.com/> 
                           

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Thursday, January 19, 2006 11:43 AM
To: [log in to unmask]
Subject: [TN] PWB SMT pad retention

Hi, Folks,
Is there a standard that specifies how well SMT pads should adhere to
the pwb? By pads I mean BGA pads that have no trace attachment, and I.C.
(gullwing) pads.
A client has circuit boards with pads that come off extremely easily
during standard rework and reflow processes. It is not limited to the
BGA pads, many other unused I.C. lead pads are also being found out of
place in the solder joints after reflow, and are easily peeled away. The
pads are not tiny flip chip pads, but standard .035" diameter pads and
rectangular .020" by .030" pads. The reflow peak temperature is only 210
deg. C for about 40 seconds. The rework is at 200 C. for 30 seconds.
Also, any speculation on the cause? This problem is limited to a single
PWB part number.

---------------------------------------------------
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
-----------------------------------------------------

---------------------------------------------------
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
-----------------------------------------------------