Steve,
I see where you're leaning with this. My thoughts (maybe 1 cent worth) are
that if you're charting your measurements solely for the sake of charting,
then it's useless to measure. However, if you chart on an X bar chart, then
you will be able to see any trend info that may tell you if you're
screening process is starting to go south. Only then can you see if
something is starting to fail and then can be rectified before you produce
many boards badly. In the high volume world, you can have around 20 or so
boards on a line that potential problems wouldn't be seen until they get to
an AOI, AXI, ICT or other system. By then, you would anticipate rework or
you would pull boards off the line. At this time you could have lots of
partially or fully populated boards to investigate. The best way to do this
would be to place an inline checker (like a Cyberoptics Sentry) after
screen printing. Checking randomly (such as 20 or 25 boards) still leaves
the potential to run many bad boards.
See, I told you it would only be worth about a cent.
Jason Gregory
Manufacturing Engineer
LaBarge Inc. --- Houston
[log in to unmask]
http://www.labarge.com
Steve Gregory
<[log in to unmask] To: [log in to unmask]
M> cc:
Sent by: TechNet Subject: Re: [TN] Paste Deposition
<[log in to unmask]>
12/30/2003 12:43
PM
Please respond to
"TechNet E-Mail
Forum."; Please
respond to
SteveZeva
Hi Tom!
Yes, and those systems aren't that cheap either!
Let me just throw this question out to everybody; let's assume that the
stencil has been ordered correctly (correct thickness for the type and
pitch of the
components being placed), the printer has been set-up correctly (correct
squeegee speed, pressure, and separation speed, along with proper board
support),
is there REALLY any value added, or will things vary THAT much when using
METAL squeegee blades, that thickness measurements need to be done every 25
boards
or whatever, during a run?
I have my own opinion, and experiences about this...but I would like to
hear
what everybody else thinks.
-Steve Gregory-
> Use ASC212 for solder paste thickness and volume. Currently check the
first
> two boards at beginning of the run and every hour thereafter. Have
> experience with CyberOptics LSMII and Sentry- running a gage R&R will
reveal a lot
> about the measuring system. Depending on the system the GR&R ranged from
5 to
> 25% .
>
> Tom Gervascio
> Senior Process Engineer
> Sparton Electronics
> (352) 540-4040
>
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