Electronics Forum | Tue May 21 09:16:28 EDT 2013 | hussman
What size QFN? What stencil design and thickness are you using.
Electronics Forum | Mon Dec 04 15:23:31 EST 2017 | kojotssss
A new stencil has been purchased. to be continued.
Electronics Forum | Wed Feb 24 15:00:41 EST 2010 | wrongway
We just stencil the part not the pads if you stencil both then you probaly have to much paste the QFN will lift becuse of the center pad. if the question is screen the part or the pad our boards have parts so close to the QFN that stenciling the pcb
Electronics Forum | Mon Feb 28 12:01:30 EST 2005 | Bob R.
We use QFNs in automotive products and have done a good bit of experimenting with pad designs, paste patterns, stencil thickness, and thermal via patterns. All of them have an effect on assembly and thermal cycle reliability. There is not a yes or
Electronics Forum | Wed Mar 15 08:18:29 EDT 2017 | rob
It's well documented in higher power semiconductors where thermal interface materials are used, such as SIL pads, thermal grease etc. There are a couple of papers on the effects of voiding on MOSFET performance, but I haven't got around to reading
Electronics Forum | Wed Nov 14 01:00:20 EST 2007 | reypal
recently, we also have problem with QFN around 3% defect related to soldering. from the cross section it turns out to be solder crack. it could be the paste volume on the center pad is too much causing QFN to float that eventually will cause crack on
Electronics Forum | Thu Mar 28 13:19:14 EDT 2019 | davef
There is no industry standard for BTC stand-off height. "IPC-7093A Design and Assembly Process Implementation for Bottom Termination SMT (BTC) Components" just finished "Final Draft for Industry Review" in December 2018. It mentions stand-off height
Electronics Forum | Thu Mar 28 15:53:49 EDT 2019 | SMTA-Jon
As a CM, we don’t have a lot of input on the PCB layouts we receive. Some engineers/software packages output the paste layer 1 to 1, some do an across the board reduction, and some set each part up individually with different reductions per footprin
Electronics Forum | Wed May 22 19:10:47 EDT 2013 | anvil1021
We do a lot of these devices and I guess I am not familiar the term "Dry Solder". The QFN device is not designed to have a drain hole, but needs to have thermal vias to control heat in most cases. We have used every possible gnd pad design and modifi
Electronics Forum | Mon Mar 25 21:50:10 EST 2002 | davef
Some of this was copped from Fred. There are numerous package types that now fall under the rubric of land grid array [LGA]. Land grid devices [ie, Bumped Chip Carrier� [BCC], LGA, Quad Flat-pack No-lead [QFN], MicroLeadFrame�, etc] are essentially
