> How do you put the glue down and place the parts(auto/manual)?
Automatically with a Aysemtek piece of equipment utilizing syringe feeders.
> Is it all SMT components or fine pitch only?
SMT components Chip resistors & capacitors at this point. We anticipate
having more problems when we start seeing the fine pitch devices we are
currently designing into new designs though. this is the reason for our
concern today.
> And your process is glue, place, wave, correct?
Glue, place, cure, wave.
> reflow? No
> And the parts come out of wave skewed or out of the placement process
skewed?
Our problem is that at times not only are parts skewed before curing but
they are missing because the glue dot did not contact the part properly
(according to our mfg. people pad height is the suspected problem). We use
Universal GSM equipment for placement.
I really appreciate the feedback on these subject thanks again.
Steve
----------
> From: Lainie Loveless <[log in to unmask]>
> To: [log in to unmask]
> Subject: Re: [TECHNET] SMT Coplanarity issues
> Date: Friday, September 26, 1997 7:35 AM
>
> >... not shelf life but rather
> > the ability to place surface mount components on a dot of glue
> > consistently. What we are seeing is a variation of up to several
> > thousandths of an inch in pad height. Our vendor has done the required
> > tests to J-STD-003 and he complies to the solder float test for
> > solderability.
>
> I'll take a stab at this one. Your "vender" is for the boards? How
> do you put the glue down and place the parts(auto/manual)? (I apologize
if you've
> covered these before, I wasn't paying attention before this message).
> Is it all SMT components or fine pitch only (mentioned later in your
> message). And your process is glue, place, wave, correct? No
> reflow? Cure of the epoxy? And the parts come out of wave skewed
> or out of the placement process skewed?
>
> If your problem is w/ placement, do a repeatability check on your
> placement equipment. Calibration is limited by repeatability
> achieved.
>
> If your problem is only evident after wave, then perhaps your epoxy
> is not strong enough for the weight of the part at the given
> temperature? We only glue, place, cure, wave with discrete chip type
> components on the bottom side of boards. We also use the
> SMALLEST glue dot that will hold the part. While this causes us to
> lose the occassional part in the wave (inadequate glue), it limits
> any shifting.
>
> One last question, are the boards somehow subject to a jarring motion
> prior to the cure of the epoxy? I know we occassionally have a
> problem with a smooth transfer on conveyors...
>
> Tell me what you think.
>
> Regards,
> Lainie Loveless
> General Atronics Corp
> Wyndmoor, PA
> (215) 242-7336
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
##############################################################
|
