Chris,
Most tape pockets have holes in them on the bottom of the pocket. Some
older feeder designs had push up pins to push the part up for the nozzle to
grab the part. I don't know of many modern machines that use this
technique, but the tape still employs this feature. The fine pitch pockets
may not have these holes (that could allow moisture) , but, nonetheless, I
would still wonder about moisture "leaching" through the seal (if it's not
absolutely sealed). This assumption is that the reel was left out of a
controlled environment.
Jason Gregory
SMT Production Supervisor/
Integrated Product Team Leader
LaBarge Inc.
(918)459-2367
(918)459-2221 fax
[log in to unmask]
http://www.labarge.com
Chris Murphy
<chris.murphy@TAI To: [log in to unmask]
T.CO.NZ> cc:
Sent by: TechNet Subject: Re: [TN] SOT 23 placed upside down
<TechNet@listserv
.ipc.org>
07/10/2003 03:22
PM
Please respond to
"TechNet E-Mail
Forum."; Please
respond to Chris
Murphy
Hi Howard,
we have been picking fine pitch QFPs up to QFP100 size from tape for years
with no coplanarity or moisture issues.
There are no problems with lead damage caused if the tray is knocked by an
operator when loading the tray into the tray
feeder and parts jump out, there is no possibility of incorrect rotation
caused by an operator putting the tray in the
wrong way around, less downtime from reel / tray changeovers as we can fit
many more parts onto a reel than a tray, no
reduced placement efficiency if you have a placment machine with a slow
tray feeder.
I am curious as to why people are baking their parts? Surely if you keep
it in it's vacuum package until it is needed
and store it in dessicant cabinets when off line then it should be OK?
(Sorry if this is a stupid question.)
Regards,
Chris Murphy,
Production Engineering,
Tait Electronics
Francois Monette wrote:
> Howard,
>
> For your second question, another important consideration for Tape Vs
Tray
> is whether the components are classified moisture-sensitive and what MS
> level. Even for robust components like BGAs, keep in mind that the
benefits
> you get from tape and reel can be more than offset by the fact that you
will
> have more parts per unit resulting in longer exposure time and especially
> the longer bake time required. In a high temp tray the default bake cycle
is
> 48 hours at 125C and in a reel it is 79 days at 40C...(ref. J-STD-033A).
>
> Francois Monette
> Cogiscan Inc.
>
> Date: Wed, 9 Jul 2003 10:16:59 -0600
> From: Howard Watson <[log in to unmask]>
> Subject: SOT 23 placed upside down
>
> Dear Technet folks,
>
> I am obviously not following the search protocol properly for the
> information that I need, so I'll just post my Q's anyway. First question
> relates to a problem I'm experiencing with some SOT 23's that get placed
> upside. This occurs on multiple machines/feeders, and my hunch is that
> the component somehow is flipping upside down in the pockets while in the
> feeder. Anyone have experience with this problem? I did change the
laser
> centering parameters so that it gets rejected now if it's upside down,
but
> I'd like to figure out the root cause.
>
> My second question is regarding QFP components in trays or tape & reel -
> is there a standard or recommendation for putting fine pitch QFP's in
> trays verses tape & reel? In other words, are 25 or 20 mil pitch gull
> wing QFP's OK to be supplied in tape & reel, or should they be in trays
to
> avoid lead damage? We always get these components in trays, and I
figured
> it was to protect the leads, but now I wonder if tape & reel is fine.
I'm
> sure it depends somewhat on the feeders, and their ability to deliver the
> components without damaging the leads. Any advice will be greatly
> appreciated.
>
> Howard Watson
> SMT Manufacturing Engineer
> AMETEK/Dixson
>
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