>>> Ryan Grant <[log in to unmask]> 09/18/01 02:14PM >>>
Hi Rich,
I've seen that problem. The fix is bigger build orders; not exactly
possible with prototypes. Luckily for you, your situation does force you to
employ good shop practices. First, make sure your pick and place programs
are built from CAD data and NOT manually at the machine. Second, make sure
your fiducial data for pick and place programs are built from CAD data and
NOT manually at the machine. Third, if component placement is off, fix the
machine (i.e. calibrate) and not the CAD locations. Fourth, if an
individual component is off, but all others are on, go back to the CAD file
and find out why the centroid is not correct, and fix it there. In short,
you should never "tweak" your pick and place machines or their programs.
Although I will admit that it is easier to "tweak" than fix the source of
the problem. Finally, make sure you have a feedback loop. Through the
course of fixing problems, make sure the "fix" is incorporated back into
program generation. For example, if a part definition is made or fixed,
make sure the new definition or fixed part definition is put in a data base
that will cause it to be used the next time around.
Good luck!
Ryan Grant
Advanced Technology Engineer
MCMS
(208) 898-1145
[log in to unmask]
> -----Original Message-----
> From: Jack Crawford [SMTP:[log in to unmask]]
> Sent: Tuesday, September 18, 2001 12:20 PM
> To: [log in to unmask]
> Subject: Re: [TN] SMT Process Validation
>
> >>> Rich Lasko <[log in to unmask]> 09/18/01 12:56PM >>>
> Good afternoon everyone,
>
> We have been doing some smaller qty prototype or very low volume
> production
> runs (Qty 5-10pcs) on our SMT equipment. We have been encountering some
> low
> yields at the SMT inspection for this type of production/prototype runs
> (They are nearly fixing each board for some reason or another). The
> feedback that I am getting from that department is that they can not
> accurately "tweak" the process with this low number of qtys (by the time
> they get close to having the machine programs set, they have completed all
> the boards in that order). So the next time we run the job, we continue
> to
> "tweak" the process in order to improve the yields.
>
> What this has caused us is some continuous rework at the end of the SMT
> line
> repairing the slid, shifted, or tombstoned components or incomplete solder
> reflow.
>
> Have any of you encountered a similar type experience and if so how was it
> handled in order to improve the yields?
>
> Thanks in advance for your help on this matter.
>
> Rich Lasko
> Badger Electronics
>
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