Electronics Forum | Thu May 29 17:19:51 EDT 2008 | dyoungquist
On 0402s we use 20x25 mil pads with a 15 mil gap between the pads on the pcb with ENIG finish, 5 mil stencil with a 1:1 aperture (20x25 mil) and SAC305 lead free solder paste. We very rarely see any tombstoning on 0402s using this setup.
Electronics Forum | Thu May 29 14:35:37 EDT 2008 | rdmundo
Gents, We've been using a round 1:1 aperture for a 5 mils thickness on our stencil design on 0402 and recently, IPC guidelines recommend oblong, homeplate or reverse homeplate. I believed the PCB pad for 0402's area within the recommended size/dimen
Electronics Forum | Tue Feb 04 17:24:07 EST 2003 | jonfox
we have some pretty tight 0402 placements and our best fix was to reduce the pad (vertically speaking) from .030x.022 to .020x.022. Fewer tombstones and the paste flows out to the edge of the pads nicely. Only difference is that we have a 6mil sten
Electronics Forum | Tue Feb 04 09:03:45 EST 2003 | Russ Roberts
Greetings, I am pretty new to SMT production, and have learned much from this forum. I am getting ready to build a CCA with many 0402 parts that are really close together. I consider these fine pitch. The board also has two QFPS, so my stencil design
Electronics Forum | Tue Feb 04 22:28:16 EST 2003 | davef
You could reduce the paste by about 70%. Solder balling and tombstoning will be the issues to fight. The drivers to these don't change with the component size. Use the fine SMTnet Archives for background. Aperture Size and Thickness of Solder Pas
Electronics Forum | Tue Apr 13 08:25:15 EDT 2004 | arcandspark
I would have gone to a .004" stencil but again, the board designers, which we have no control over or are we allowed to give input to, have made the pads on all connectors and many other parts so small that we are almost seeing insuffecient solder us
Electronics Forum | Thu Apr 29 11:07:03 EDT 2004 | arcandspark
You are right about the very poor support for smaller customers. I had told them we were looking for another paste and now they have sent the reginal manager and the US sales manager has come by to see what they can do for us. All they keep saying is
Electronics Forum | Mon Apr 07 13:02:30 EDT 2003 | kmorris
Sorry, I forgot to include the stencil thickness. It is 5 mil. Thanks for the input, everbody. I just checked with our stencil supplier & I thought that Electro-polish was standard with lazer, but I now find out it is not. Our stencil did not get
Electronics Forum | Mon Apr 07 11:39:55 EDT 2003 | russ
How thick is your stencil? We print 16mil every day with type 3 paste 2 of which you have tried (Alpha and Kester) Stencil should be 5 mil. Russ
Electronics Forum | Mon Apr 07 12:21:02 EDT 2003 | davef
Russ is correct. A 5 thou thick stencil should give good release. Here's how you run through it: * You want at least 5 solder particles across the smallest aperture. So in your case, 8 thou wide, which equals to 0.20mm gives us 0.20/5=40 microns.
