Electronics Forum | Mon Sep 20 17:46:21 EDT 1999 | Dave F
| I've had some trouble pasting a test board for a MicroBGA trial. Most of the paste remains in the stencil apertures. | The stencil is 6 mil thick, laser cut and electo-polished. | The apertures are 12 mil in diameter with 20 mil pitch. | We are usi
Electronics Forum | Tue Sep 18 19:32:49 EDT 2007 | davef
Welcome Jimmy Let's mince words to help focus on the issues. When you say "QFP area solder paste shifted," do you mean: * Paste printed on land pattern perfectly, but moves after printing. * Paste printed off the land pattern, even though the stenci
Electronics Forum | Wed Sep 19 21:08:28 EDT 2007 | wailiang81
Those others parts also happend printed not accurate, but there is no solder problem. Only the QFP area looks bad condition.
Electronics Forum | Wed Sep 19 09:48:38 EDT 2007 | slthomas
In addition to what DaveF said, I'd like to know if there are other parts on this pcb, and if the paste for those parts was printed accurately or not.
Electronics Forum | Wed Sep 19 13:38:43 EDT 2007 | russ
What is your alignment method for printing? Vision? Mechanical? What is the advertised repeatability for your machine? Russ
Electronics Forum | Wed Sep 19 21:04:57 EDT 2007 | wailiang81
Hi,davef, thanks for your concern. The condition was the pasted printed off with around 0.8~0.9mm from the land pattern. This will easy observe at QFP area. At fiducial, the stencil seens aligned accurately. Once solder bridge happend, its easy to
Electronics Forum | Tue Sep 18 12:10:39 EDT 2007 | wailiang81
Hi, good day to all. This is my 1st question post in this forum. Hope able to share some knowledge here. As we know QFP area like 0.4mm pitch was a very critical area to control especially those PCB using silkscreen printing process manufactured. Onc
Electronics Forum | Mon Oct 14 14:11:39 EDT 2013 | island2013
Yes, I agree with Evtimov. It's more about aperature reduction and type than it is the type of machine. Aspect and and Area Ratio are very important. Take a look at this page I found on the internet http://www.qualiecocircuits.co.nz/stencil-techno
Electronics Forum | Tue Feb 07 16:32:13 EST 2023 | glasscake
Good ventilation is also important to removing aerosols and other vapors. Make sure your building HVAC is pulling in a good portion of outside air. If people are complaining try to up the ratio of recirculated/outside air. This will add cost dependin
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
