Electronics Forum | Thu Feb 23 23:24:14 EST 2006 | KEN
Depends what is adjacent to the step. 1206 chips could reside closer than say a 16 mil fine pitch. Larger apertures are more forgiving to height variations than small apertures.
Electronics Forum | Mon Feb 18 12:09:17 EST 2013 | pbarton
What type of flux material does your solder paste have? I have seen difficulties when attempting to print small apertures with water washable and rosin types. Do you get a good first print and then have problems or is it the same from the start?
Electronics Forum | Sat Sep 30 12:14:32 EDT 2000 | jarnopy
Hi Maybe you have too small apertures in stencil. Good apertures size is 90% from pad. And one thing what you can try is that you cut your stencils(blades) aperture corners round (i mean like a oval). I hope that these advices can help you.
Electronics Forum | Wed Sep 01 11:09:45 EDT 2004 | burgosa
We are considering the CyberOptics SE300 for solder paste inspection at post-stencil print. Does anyone have experience with this AOI machine? How it works with small apertures like 0201's and uBGA's? Comments are welcome. Thanks
Electronics Forum | Mon Jan 09 08:25:30 EST 2006 | grantp
Hi, If the stencil was not cleaned well from the previous run, dried paste residue can cause the paste to grab in the stencil. If you have a microscope, check the small apertures for contamination. Regards, Grant
Electronics Forum | Mon Nov 12 09:13:50 EST 2007 | russ
Chunks is right, reduce center pad by 50% print the signal pads at 1:1. this will ensure you solder QFNs fine regardless of the actual part. If you are not printing then it is process capability issue and has nothing to do with QFN but rathjer small
Electronics Forum | Thu Apr 30 13:09:53 EDT 2009 | scottp
One factor I see missing is separation speed (or snap off speed). I've run experiments with different pastes where it was the biggest factor in standard deviation of print volume for small apertures.
Electronics Forum | Fri Jul 05 11:45:47 EDT 2002 | stefwitt
I have seen the U-shaped aperture on a customer site, being used with success. However, the problems with the stencil and the �loose� tabs where reportedly a reason to search for different aperture designs. Before this company could test their ideas
Electronics Forum | Fri Nov 10 09:13:34 EST 2006 | russ
Dave hit the cons pretty well for type 4 type 4 is used when you have extremely small apertures and type 3 will not fit into them or release adequately basically. I have not yet had application that requires it but got very close once, .007 circle
Electronics Forum | Mon Aug 13 12:38:38 EDT 2012 | grahamcooper22
Maybe the area ratio between the sides of the stencil apertures and the aperture opening is too low for the spec of the paste ? So it will tend to stick in the apertures. ...only solution is thinner stencil or a paste that can release easily when are
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