Hi Jeff,

You're in luck as far as machine placement.  Components will move closer
to the center of their respective pads due to the surface tension of the
solder.  If you do double sided boards, the components riding upside
down will get a second chance to re-center without the friction of their
leads slowing them down.

Unfortunately for your designers, it is not uncommon for the laminate of
the circuit board to stretch 0.005" over 10".  No matter how accurately
you place the components on their pads, the laminate could push the true
position out of tolerance.  However, this can be solved by setting a
mating datum close to the placement of the bezel.  This will restrict
PCB stretch or shrink to a local area and will only be on the order of a
mil or two.

Ryan Grant

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of McGlaughlin, Jeffrey
A
Sent: Monday, February 16, 2004 1:54 PM
To: [log in to unmask]
Subject: [TN] Pick-and-place Tolerance


Help all -

I need to know if there is a predictable tolerance on parts placement
AFTER REFLOW.  I am fairly sure the pick-and-place equipment we" use is
stated to be repeatable to 0.005" with an angular accuracy of 1/2
degree, but that is before reflow is there a metric or formula for
determining true position tolerance of component placement for post
reflow?  The reason I am asking is that our mechanical design group has
designer a bezel for a display panel that has a true positional
placement requirement of 0.006 on our finished array of 246 large SMT
LEDs.

Thanks for the help,

Jeffrey A McGlaughlin, CID
Engineering Designer
Battelle Memorial Institute
Columbus Ohio
http://www.battelle.org
[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
-----------------------------------------------------