Electronics Forum | Wed Mar 07 14:19:04 EST 2007 | cyber_wolf
We use quite a few Invar stencils. I have several stencils that have apertures that fall below aspect ratio that work very well.
Electronics Forum | Sun Sep 27 22:39:55 EDT 2009 | rajeshwara
The same issue i faced 2 yrs before , i sugest 1. Use stencil of 4 mils ( Take care of Aspect Ratio and Area Ratio ). 2. Use Solder Paste of Type 4.5 and Viscosity in between 1100 to 1300. ( Try Solder Paste of Cookson or Alpha metals : OM338 T45-L
Electronics Forum | Thu Mar 03 18:09:06 EST 2005 | gpaelmo
We also use Indium NC-SMQ92J. We do the same as mentioned per Russ. We reduce apertures mostly on QFP's with pitch of 25 mil or less (we place down to 15 mil QFP). All other apertures we keep 1:1. We print resnet 0805 size with no problems. You might
Electronics Forum | Fri Sep 21 10:56:38 EDT 2001 | davef
Not as such. Look at IPC-7525 �Stencil Design Guidelines� The issues are: area and aspect ratios. They relate the size of the aperture opening to the thickness of the stencil. Check the fine SMTnet Archives for guidelines.
Electronics Forum | Sat Sep 28 05:30:44 EDT 2002 | ivanchu
Stencil cleaning process is taking by machine every 15 boards. We are using wet, vaccune, Dry, Dry cleaning process. The aperture of the stencil is fullfil the aspect ratio.
Electronics Forum | Tue Jun 24 10:38:47 EDT 2003 | ehess
Bruce, I have a spread sheet, in Excel, that helps in determining stencil thickness, based on smallest aperture size. If you are interested, I can email you this.
Electronics Forum | Mon Dec 14 15:08:46 EST 1998 | Jim Mitchell
Provided your software supports board stretch and the board is stretched in a linear fashion, you should not need fiducials for each image. If you do elect to use local fiducials, Quad recommends a single fiducial. This method is faster and you can
Electronics Forum | Tue Jul 31 00:48:55 EDT 2001 | Frank
Sorry I forgot to provide enough information. Stencil thickness is 6 mil Aperture width is 10 mil Aspect ratio (aperture area / wall area) = 0.72 Solder paste mesh size, type 3 (-325 +500) With this aspect ratio we can printing without any probl
Electronics Forum | Thu May 18 10:20:55 EDT 2006 | slthomas
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 r
Electronics Forum | Tue Apr 01 18:21:48 EST 2003 | slthomas
I've never printed adhesive but I assume that aspect ratio still plays a part with release. Maybe that .006" is just to thick to get good release. Can you step your stencil down from .006" to .004" or .005" for the 0402's?
