Todd

I had come across this problem few months ago and the printing was
nightmare. The aperture width was 8 mils.
Try the following(it worked for me with aspect ratio below 1.5):
1. Lasercut with Eletropolish
2. Ni plate-it really improves release
3. If still not okay, try Type4 paste if you are using Type3 paste.
4. Snap-off might also help.Metal sqeegees , press and speed adj may
help.
5. Use fresh paste (first time usage)
or Try out electroformed stencils. Expensive stuff. I could not try that
due to cost constraints.

Talk to me offline if you need to discuss your case in specific.

Ashok Dhawan P.ENG.
Manufacturing Engineering
Unisys Canada Inc.
51 Burmac Road
Winnipeg R2J4C9
CANADA
Fone 204-257-9199
Fax   204-257-9104

> ----------
> From:         Charles Barker[SMTP:[log in to unmask]]
> Sent:         July 10, 1998 1:28 PM
> To:   [log in to unmask]
> Subject:      Re: [TN] Electropolishing Laser-Cut Stencils
>
> Todd, you do not say how thick this stencil is.  With all this
> polishing
> and plating, could your opening have decreased below the 1.5:1 ratio?
>
>
>
>
>
>
> Todd Ness <[log in to unmask]> on 07/10/98 04:13:28 AM
>
> Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please
> respond
>       to Todd Ness <[log in to unmask]>
>
> To:   [log in to unmask]
> cc:    (bcc: Charles Barker/US/I-O INC)
> Subject:  [TN] Electropolishing Laser-Cut Stencils
>
>
>
>
> Hi all,
>
> We are currently having problems with a laser-cut stencil that is
> electropolished and nickel plated with 9-mil openings. The paste does
> not release well from the apertures. We are having to wipe after every
> print. The board is fixtured well and we have been using the same
> paste for the last two years. We had a different laser-cut stencil in
> production from a different manufacturer with the same 9-mil opening,
> but this stencil was not electropolised or nickel-plated. With this
> stencil, the paste release was excellent and we never had to worry
> about wiping.
>
> Does anyone have any input into whether or not laser-cut stencils
> should be electropolished and nickel plated? I have heard
> contradicting opinions on this subject. One source has said that you
> do not want to electropolish laser-cut stencils because the
> rough laser walls will give you a better paste release. Whereas,
> another source has said that the smooth laser walls will give you a
> better paste release.
>
> Also, what benefit does nickel plating give you? Does the paste tend
> to roll better with nickel plating? Do you tend to get more or less
> paste deposit on the boards with nickel plating? Does it increase the
> life of the stencil?
>
> Has anyone using laser stencils seen major differences between
> the quality of different stencil manufacturers?
>
> Any input into this subject would be greatly appreciated.
>
> Thanks,
> Todd
>
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