Electronics Forum | Mon Apr 16 16:24:20 EDT 2018 | slthomas
Amazingly enough, every one of these held fast where we placed them with a paste brick sized 1:1 with the thermal pad, no sectioning. Yes, there were voids, but we can live with that in this application.
Electronics Forum | Fri Jul 13 19:35:02 EDT 2007 | hegemon
We have had good success doing pb Free QFN work. Typically for the center pad we use ~68% coverage with 1:1 ratio on the perimeter pad. For the 68% coverage we have tried cross hatch pattern, diagonal stripes, dot series, and most successfully a clo
Electronics Forum | Wed May 20 17:56:51 EDT 2009 | dyoungquist
I have attached a pdf showing the dimensions for the QFN we placed. First, The pins on the part are not only on the bottom side but also wrap around to come up each of the 4 sides of the part as shown in the side view in the attached pdf. This i
Electronics Forum | Sat May 18 10:21:09 EDT 2013 | davef
isd.jww: Comments are: * Current thinking has flux volatiles being the major contributor to voiding, not scavanging by via * I have no reason to think that 0.3mm via won't gladly accept solder. Plug them, if that's a concern. * If your concern is ina
Electronics Forum | Sat Jun 05 13:38:22 EDT 2021 | ppcbs
For Linear Tech LGA's we solder bump the LGA using a .30mm solder ball then reflow with a tacky flux. This will provide a void free solder joint and adds a little height to the solder joint in case you use a flux that you want to clean from under th
Electronics Forum | Wed Mar 27 04:32:49 EDT 2019 | pavel_murtishev
Charliem, Thank you for the input. Following this logic, in case if there are no soldering issues, pad coverage and voiding levels are within acceptable limits and a gap between BTC and pad let us say 200um, this could be accepted, right? IPC-A-61
Electronics Forum | Tue May 07 10:36:38 EDT 2019 | slthomas
Probably just means you started out with an optimal profile. I suspect that not everyone does. ;) It seems like we did have some luck with profile adjustments in one instance with some QFN's with a large thermal pad. Like I said, though, the profi
Electronics Forum | Thu Oct 26 10:29:03 EDT 2006 | Mike
First, Voiding under thermal pad is unavoidable(pardon the pun), unless you can find a way to add sufficient amount of solder paste to cover the area, and match that solder volume on your terminal leads. I build HVM qty's of "QFN" components w/ therm
Electronics Forum | Fri May 17 20:11:32 EDT 2013 | isd_jwendell
I am familiar with TI's documents on QFN mounting. I do not have an X-Ray machine, so I worry about excessive voiding that could happen with using the thermal vias improperly. As a general rule-of-thumb, I print paste with a 25% reduction on the ther
Electronics Forum | Mon Nov 19 13:13:51 EST 2007 | hegemon
We have found differing results based on the pattern used when reducing to total % of solder paste on the center pad. We arrived at 68% coverage on the center pad, and 1:1 for the perimeter pads. To get the 68% coverage we used a number of differen
