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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


fine pitch printing

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#41597

fine pitch printing | 17 May, 2006

I'm having trouble printing leads on a fine pitch part. The lead is only .008". I'm using a DEK 265 with metal squeegee and using WS200 multicore solder paste.The stencil is laser cut and polished. I've experimented with different pressures and different angle squeegee's. I still cannot get a consistant print (voids). Please help!!-----Pitch is .017" and stencil thickness is 8mil.

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RDR

#41598

fine pitch printing | 17 May, 2006

So, what is the pitch of the part and the pad size, also tell us the thickness of stencil.

Russ

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Chunks

#41628

fine pitch printing | 18 May, 2006

Hi dwelch123,

8 mils seems a bit thick to me. I would normally go 6 or 5 mil for fine pitch such as this. One other area to check is the the snap off. Are you using the slow snap off or just lowering the board right after print? If so you should notice the solder paste stuck in the stencil apps. where you have voids on the board. If not, your voids may be caused by the paste not getting through the apps of your stencil.

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#41634

fine pitch printing | 18 May, 2006

Russ asks good questions and I think Chunks pretty much nailed it.

Aspect ratio (aperture width/stencil thickness) s/b 1.2 minimum (I like 1.5 if I can get it). If your aperture width = lead width (.008"), yours is 1. Tough to get consistent paste release with a 1/1 aspect ratio. Personally I would go to a 5 mil foil for anything below 20 mil pitch.

Also the condition (age, storage methods) of your paste can contribute, as well as you alignment (gasketing), lift speed, and squeegee pressure and condition.

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RDR

#41647

fine pitch printing | 18 May, 2006

Go 5 or 6 mil thick with stencil, i am not familiar with that pitch but I would recoomnd a 5mil.

Was the thickness in this post before and i missed it?

Russ

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#41656

fine pitch printing | 18 May, 2006

I think he edited his original post.

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