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Paste in hole question

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#56014

Paste in hole question | 18 August, 2008

We are in the process of preparing for a new board that requires paste in hole processing. The hole is a .020" via, and our customer wants it filled with solder, but not bulging past flush. For printers,we use a DEK 249 with a squeegee, and a DEK 260 with a ProFlow cartridge. Our paste is 90% metal, and our screens are .006" thick. Does anyone have experience with this processing that could offer advice? Any thoughts on apperature size? Thanks for any help.

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#56015

Paste in hole question | 18 August, 2008

I belive this could be done in the board fab process better than trying to do it with paste.

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#56016

Paste in hole question | 18 August, 2008

Stencil apertures are cut to deposit solderpaste onto the annular ring, provided its wide enough. Then you can place a solder preform if needed to ensure there is enough solder to fill the barrel. Here is some information on solder preforms:

http://www.indium.com/products/solderfabrications/preforms.php

Also, web search "pin in paste process" and there is a wealth of info on the process. DEK I'm sure is a good resource too.

Here;'s a link to an article in SMT mag.:

http://www.indium.com/documents/techpapers/SMT_PIP_article-English_6.05.pdf

Also, what Doug says has merit. I guess he's referring to the SiPAD process?

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#56018

Paste in hole question | 18 August, 2008

No I was actually thinking more on the lines of this. http://pcdandf.com/cms/content/view/3845/95/

I think if you try and put solder in the hole you will not have a flat or well filled hole in the end.

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#56021

Paste in hole question | 18 August, 2008

We do it all the time for air pressure reasons. Use a 6 mil stencil, print right on the via, aperture opening 100% same size as the via, on an 0.063" thick board. Doesn't leave a bulge and plugs the air. You can have your board house do this for you too fat a cost.

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#56025

Paste in hole question | 18 August, 2008

Real Chunks, Does "aperture opening 100% same size as the via" mean, aperature the same size as the hole, or the barrel of the via. If that makes any sense. Thanks

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#56029

Paste in hole question | 18 August, 2008

Oops, I thought it was for components- not filling via holes. Yeah, getting it fab'd in would be the way to go I would think.

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#56030

Paste in hole question | 18 August, 2008

Open the same size as the via's anular ring. Any slight off print will wet its way back into the via hole.

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#56038

Paste in hole question | 18 August, 2008

Volume of paste = 2X volume of the hole

Questions are: * Why does your customer want the hole filled with solder? * Would materials other than solder be acceptable? * We assume 0.020" is drill size. What is the finished size of the hole? * What is the finished thickness of the hole? * What is the surface finish of the board in the vacinity of the hole?

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