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September 1998

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Subject:
From:
Mike Barmuta <[log in to unmask]>
Reply To:
Date:
Tue, 22 Sep 1998 13:16:48 -0700
Content-Type:
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TEXT/PLAIN (97 lines)
        Afri: Since no information was provided on your current process it's
hard to give you an objective critique on what to change. Let me give you some
information that may help you.
First you will not be able to keep mask out of all the holes with this type of
equipment, although it can be minimized.
Second, the mask in the holes of the outside edges on the panel is due to the
physics and dynamics of sreen printing.
Third, it is very important that the squeeges are parallel in all axisto
minimize mask deposition in the holes.

I will assume you are printing 18"X24" panels that are 0.062". If the panel size
or thickness is different then you will have to make changes.

1. Use the smaller off contact blocks, typically 3/4".

2. Make sure the printing edge(not the flat edge face)of the front and back
squeeges are parallel = to each other, and not crossed X. Even though you are
using blocks to set these, a better way is to extend the squeeges out against
each other with out screens or a board to verify this. Also the squeege angle
should be set at about 30 degrees.

3. Independtly extend and check the front squeege then back squeege to make sure
it is parallel - left to right of its printing head and shuttle track, not
canted /. This can be further checked by placing a board between the two
squeeges when they are extended at the same time. The board should be slightly
raised out of and above the shuttle track about a 1/4". The panel should be
directly above the shuttle bar and parallel to it. It should be true to X znd Y,
not skewed or slightly rotated. If it is then your squeege extension bars and/or
heads are not set right.

4. Orient the panel so it is in the 24" top to bottom, 18" left to right
direction. make sure you set your shuttle stops so the panel is centered to the
screen, not offset. You want to print as close to the "sweet spot" i.e. center
of the screen as possible.

5. Use a 22" squeege(1-2" wider per side than the panel), squeege pressure 90psi
fixed head, 80psi floating head; you can try backing this off as long as you
don't get skipping of the print. Start with something around a 90 mesh screen at
20 newtons, you can go to a higher mesh count to lesen the deposit but make sure
you don't get too thin or a starved print.

5. Start with a print speed around 2.5 ips you can go faster or slower to vary
the deposit depending on the rheology of your mask.

One word of caution, the Circuit Automation is a great machine but it seems like
everyone out there is a little different. You know the old constant improvement
creedo. So these are things we have found to work for us, yours may be
"different".

                                                Regards
                                                        Michael Barmuta
                                                        Staff Engineer
                                                        Fluke Corp.
                                                        Everett Wa.
                                                        425-356-6076
On Mon, 21 Sep 1998 15:11:50 -0700 Afri Singh wrote:

> From: Afri Singh <[log in to unmask]>
> Date: Mon, 21 Sep 1998 15:11:50 -0700
> Subject: [TN] DP-1500 (fwd)
> To: [log in to unmask]
>
> HELLO . CAN SOMEONE TELL ME WHY DO WE GET SO MUCH INK BEING PUSHED INTO THE
> HOLES ,ESPECIALLY ON THE CORNERS AND THE BOTTOM 2 INCHES OF THE PANEL ON
> THE CIRCUIT AUTOMATION UNIT.
> WE WERE TOLD TO MAKE SURE THE SQUEEGES WERE ALIGNED USING THE BLOCKS.  THIS
> HAS NOT HELPED.  I HAVE HEARD MANY PEOPLE HAVE HAD THIS PROBLEM AND
> MODIFIED THE UNITS THEMSELVES -CAN THEY SHARE THIS INFO
> THANK YOU
>
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