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SMT electronics assembly manufacturing forum.

Solder Paste Printing to 0.005

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Solder Paste Printing to 0.005 | 27 December, 2010

Does anyone have any experience in printing solder paste on a 0.0065" pad?

I have a requirement to attach single chips with 600 to 2400 connections. The chip has a 0.005" solder ball, 0.010 pitch. Attaching to a substrate with a 0.0065" pad.

Any suggestions on a good solder paste that will print this fine? I'm not having any luck with a standard stainless steel stencil. I am going to try a stick-n-peel stencil.

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Solder Paste Printing to 0.005 | 28 December, 2010

Use a 0.002" to 0.003" thick stencil. Use an electroformed stencil from Photo Stencil or one of the others. Use -500 +635 paste or a -500 paste or type 5 or greater paste.

I have printed at 0.008" pitch with 0.004" pads. It can be done.

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Solder Paste Printing to 0.005 | 4 January, 2011

We've been doing this for over 10 years using flux. We print a tacky flux first using an 0.002 or 0.003" thick stencil, then print paste using a thicker stencil with the underside half etched to keep it away from the flux. In our case, we can't just print paste for everything using a smaller stencil because we're in the high reliability market. Another option would be to dip flux the component.

We do have one application using solder paste with a type 5 powder and a 0.002" thick stencil. In that case, we have to use paste instead of flux because the device uses a stud rather than a solder bump.

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