Electronics Forum | Fri Dec 05 11:13:06 EST 2008 | dilogic
We are running an older GSM1 machine (sw.runs on OS/2) and I would appreciate any hints which vision algorithm to use for best results with QFN and similar parts. One of the ULC's is 2.6mil/pixel. - Dejan
Electronics Forum | Mon Dec 08 14:11:14 EST 2008 | comatose
We run a bunch of .5mm qfn on a GSM1 with a 2.6mil camera, from 16 pad to 100 pad. Works like a charm. We call them a PLCC.
Electronics Forum | Thu Oct 15 11:04:28 EDT 2009 | spitkis2
Thanks Jim. Pressing the QFN into paste was what I thought of, just wasn't sure if it would cause solder paste to be pressed outside the pad area and possibly bridge with an adjacent pad. Do you recall the ratio of paste coverage to the pad area?
Electronics Forum | Mon Jan 11 13:31:54 EST 2010 | cbart
I know IPC is working on a spec for voiding for QFN'S. However since its not released I'm curious what others have defined as the max allowable % voiding on the leads (not center ground).
Electronics Forum | Wed Feb 24 01:04:08 EST 2010 | dashley
Is it necessary, or beneficial to apply solder paste on the PCB pads for QFN rework? It seems that using micro stencils is not the best approach. Any guidelines or suggestions available for paste deposition techniques?
Electronics Forum | Wed Aug 25 15:02:04 EDT 2010 | spitkis2
I am printing solder paste directly onto a QFN device. Any recommendations on the type of solder paste to use? Namely I am concerned about getting a good release from the stencil. Thanks
Electronics Forum | Thu Apr 05 08:21:52 EDT 2012 | rway
Yes, but no guarantee of solderability. This just puts more paste on the pads. From my experience, unsoldered QFN parts are not due to lack of solder, but reflow.
Electronics Forum | Fri May 17 14:56:21 EDT 2013 | davef
There's not supposed to be any effin 'drain hole.' Where's you get that from? Read this: http://blogs.smtnet.com/smt/other/qfn-btc-design-guidelines-thermal-pads-etc/ BR davef
Electronics Forum | Mon May 20 15:58:55 EDT 2013 | sevenzero
Did you try a thinner stencil? More pressure and speed in the printer? What size is the QFN? Maybe the aperture needs to have a + in the center?
Electronics Forum | Fri May 24 14:42:35 EDT 2013 | dilogic
Google for this: "weight_limit_qfn_smta.pdf" Although it is focused on QFN, formula can be used for most parts...
