Hi Evamaria:
I appreciate all your knowledge sharing. Please let
me share a clarification. Seagull lead can be represented by a leg. The
part of the lead that comes off the body is the thigh, the first bend is
the knee, the second bend is the heel and the tip of the lead is the
toe. The foot is made out of the heel, the toe ( this foot has only one
toe ), and material between the last two. I may be wrong, but my take is
that in the below mail toe reference should be foot. Toe down is when
the heel is higher than the toe (standing on your toes ) and toe up is
when the heel is lower than toe (standing on your heels). On toe down
the solder has to be to 1/2 up the foot thickness for class 2 and up to
the foot thickness for class 3. For flat foot or toe up the solder has
to be up the middle of the heel, at a minimum for previous cases.
Best Regards,
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jones, Evamaria
Sent: Tuesday, March 07, 2006 1:12 PM
To: [log in to unmask]
Subject: Re: [TN] Heel Overhang
Kevin,
A heel fillet is required for class three. It plays an important part of
the mechanical bond for the SMT device. Additionally, minimum side joint
length could be violated. J-STD-001 rev D for class 2 & 3 states, when
the length of the toe is greater than three times the width of the lead,
the minimum side joint shall be three times the width of the lead or 75%
of the toe length (whichever is longer). When the length of the toe is
less than three times the width of the lead; the minimum side joint
shall be 100% of the toe length. That portion of the toe (hopefully all
of it) is a mechanical bond to the conductive pattern on the PCB. The
side joint length is visual evidence that solder flowed under the lead
and bonded the lead to the land pattern. The goal is to bond entire toe
portion of lead to land. There is an exception call toe down
configuration where the toe portion of the lead doesn't make adequate
contact to form a good mechanical bond to the land pattern. Hence, the
minimum heel fillet shall extend to the mid-point of the outside lead
bend at a minimal. This provides more surface area to bond to.
Eva Jones
Instructor
Quality Engineer
________________________________
From: TechNet on behalf of Kevin Glidden
Sent: Mon 3/6/2006 11:29 AM
To: [log in to unmask]
Subject: [TN] Heel Overhang
Hello again.
Question on IPC-610 (class 3) criteria. For SMT solder joints, there
appear to be criteria set for TOE overhang, but not HEEL overhang. Is
this an oversite or a purposeful omission? Is there a limit on how much
the heel of an "L" shaped SMT lead can be off the pad lengthwise? The
obvious and defined limit is "does not violate minimum electrical
clearance", but does anyone else have info on this criteria?
Thanks again,
Kevin Glidden
---------------------------------------------------
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
-----------------------------------------------------
---------------------------------------------------
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
-----------------------------------------------------
|
