Electronics Forum | Wed Jan 08 14:36:44 EST 2003 | davef
It depends on your product requirements. We don't like to print off-pad, because: * Tough to control the amount of paste that squirts onto the board, because the aperture is not gasketed to the pad on the board. * Some paste that squirts between the
Electronics Forum | Tue Jun 28 13:04:08 EDT 2005 | slthomas
Are you saying that increasing the frequency of cleaning to every 3 boards *reduced* bridging, or that it's just something you tried? I don't understand why that would help(in my experience it has reduced "insufficient solder" conditions but not brid
Electronics Forum | Tue Jul 08 15:37:14 EDT 2008 | realchunks
Volume that appears to be caused by wetting. Now remember most solder pastes will not "flow" across an entire pad. It will only flow where it is printed. In your pic, if the pad was covered and came out like this - it may be your pad. If it was
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 | Thu Jul 05 15:33:12 EDT 2012 | dmiller
That's a long board! Based on your description, it sounds like board stretch may be your issue. Look at where the paste is printed on the board. If you have board stretch, you'll see the print off to the left on the left side of the board and off
Electronics Forum | Mon May 01 22:55:02 EDT 2006 | KEN
....am I reading this correctly? "Screen Printing" or "Stencil Printing" Screen = agree = off-contact.....it's fuzzy going back into the memory banks to the early 90's. Screen mesh and emulsion will stretch to produce the gasket affect while snapp
Electronics Forum | Tue May 30 16:02:04 EDT 2006 | slthomas
Do a dirty DoE...print ten boards with the worst error you think you can accept, build them up, and count print related defects. At the same time, print ten spot-on and proceed the same. If you don't have any more defects on the off-print batch show
Electronics Forum | Fri Mar 24 09:18:13 EST 2006 | Chunks
For placement tooling holes should get you close. For screen printing pads are fine. Just turn off the post print alignment if doing 2D or 3D.
Electronics Forum | Tue May 02 05:59:28 EDT 2006 | davef
We agree with Ken's points about off contact / screen versus stencil, but this DHolt is talking stencil [regardless of what is typed about screens]. Comments are: * On "smears under the stencil": smearing happens. It makes us wonder about the frequ
Electronics Forum | Fri Jan 19 15:23:22 EST 2007 | SMT GUY
Things to consider... Print alignment - Use off contact Printing and verify board supports - In machine ensure part profile is correct with correct nozzle and thickness - Use support pins in machine to limit placement bounce - Limit input from produc
