Your concern is valid. I have had experience here where handling large
boards prior to reflow increases defects because of flexing of the board,
tilting and shock and the bad effects that has with parts sitting in paste.
This problem affects both leaded components and BGAs. The board I had a
problem with was actually a routed 6-up panel, 11x13, that was quite flimsy.
It was an older product we build in our batch SMT cell and had not converted
over to our in-line cell. Therefore, the panel had to be hand carried from
the p&p machine to a bench then to the reflow oven. The more typical process
for you would be to have a fixture that takes the board right thru paste,
p&p and reflow without handling. I know the following companies make these
types of fixtures:
http://www.emcgti.com/products/fixture_pc.shtml
http://www.mb-mfg.com/mb-5000.htm
https://ascentec.securesites.com/products/process.shtml

Your customer has a choice...do the job right or accept the rework costs.
Good luck. Unfortunately, the "customer is always right."

=========================
Bob Barr
Manufacturing Engineering
Formation, Inc.
=========================

> -----Original Message-----
> From: Rick Thompson [mailto:[log in to unmask]]
> Sent: Wednesday, May 07, 2003 1:49 PM
> To: [log in to unmask]
> Subject: [TN] Reflow Fixture Opinions Sought
>
>
> We have a customer who is requesting that we use a reflow
> fixture consisting of a Durapol plate with removable tooling
> pins to accomodate several different large PWBs through the
> reflow process. These fixtures would run on the flat belt
> rather than edge rails and would require that we remove large
> (16"x12") fully loaded boards from the conveyor rails to
> install on these fixtures prior to reflow. Components on the
> board range include a number of BGAs and micro-BGAs.  The
> intent of the fixtures is to keep the board from flexing
> during reflow. My concern is that all the handling and
> flexing of boards with components in solder paste is going to
> increase the chances of soldering problems due to part
> separation from the paste if the board is flexed.
>
> Question: Has anyone used this type of concept on large,
> densely populated boards. Comments on pros and cons? Any
> other insights would be appreciated as I'm looking for
> supporting evidence to dissuade them from this approach which
> is primarily aimed as saving fixture costs over dedicated SMT
> fixtures.
>
> Thanks in advance.
>
>
> Rick Thompson

---------------------------------------------------
Technet Mail List provided as a free 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/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------